Indian Patents
Title of Invention

A DRYING APPARATUS
Abstract A drying apparatus for drying articles such as clothing is provided. The drying apparatus includes a chamber for containing articles to be dried and a system for supplying heated dry air at a first temperature to the chamber. The air supplying system comprises an air flow pathway having an evaporator for removing moisture from air exiting the chamber and for decreasing the temperature of the air to below dew point temperature. The air supply system further has a condenser for increasing the temperature of the air exiting the evaporator to the first temperature. The drying apparatus further has a heat pump system having a refrigerant loop which includes a compressor, the condenser, a TEV valve, and the evaporator.
Full Text HEAT PUMP CLOTHES DRYER
CROSS-REFERENCE TO RELATED APPLICATION
[0001] Benefit is claimed of U.S. Provisional Patent Application 60/507,466, filed
September 29, 2003 and entitled "HEAT PUMP CLOTHES DRYER", the disclosure of
which is incorporated by reference herein as if set forth at length.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a dryer for drying clothes and other things made
from fabric and to a washer for washing same.
[0003] Ordinary dryers are a study in simplicity. As shown in FIG. 30, they draw room air,
pass it over a heater, and blow it through a rotating drum containing laundry to be dried. The
air passes through the drum once, and is then vented out of the building. Some of the air
extracts moisture from the fabric, and some of it bypasses the laundry, and escapes without
doing any work. This is the simplest, least expensive, and the most fallacious way to build a
dryer.
SUMMARY OF THE INVENTION
[0004] Accordingly, it is an object of the present invention to provide a dryer which has
improved performance and efficiency.
[0005] The foregoing object is attained by the present invention.
[0006] In accordance with the present invention, a drying apparatus broadly comprises a
chamber for containing articles to be dried, means for supplying heated dry air at a first
temperature to the chamber, which air supplying means comprises an air flow pathway
having means for removing moisture from air exiting the chamber and for decreasing the
temperature of the air to below dew point temperature and means for increasing the
temperature of the air exiting the moisture removing means to the first temperature, and a
heat pump system. The heat pump system comprises means for passing a refrigerant in a
liquid state through the temperature increasing means, means for controlling refrigerant mass
flow and for converting the refrigerant from the liquid state to a liquid/vapor state, and means
for passing the refrigerant in the liquid/vapor state through the moisture removing means to
convert the refrigerant into a vapor state.
[0007] In a second aspect of the present invention, a washing apparatus is provided. The
washing apparatus broadly comprises a washing chamber, means for supplying heated water
to the washing chamber, which heated water supplying means comprises a first heat storage
device having a heat exchanger device and an inlet means for receiving water, means for
draining heated water from the washing chamber and passing heat from the heated water to a
drain side heat storage device, and a heat pump system for transferring heat from the drain
side heat storage device to the first heat storage device.
[0008] In yet another aspect of the present invention, a drying chamber for use in a drying
system is provided. The drying chamber comprises a stationary drum and a plurality of
rotating vanes for tumbling the article to be dried.
[0009] Other details of the heat pump clothes dryer of the present invention, as well as
other objects and advantages attended thereto, are set forth in the following detailed
description and the accompanying drawings wherein like reference numerals depict like
elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic illustration of a dryer in accordance with the present
invention;
[0011] FIG. 2 is a schematic representation of a dryer with a warm up heater;
[0012] FIG. 3 is a schematic diagram of a dryer with an external warm up evaporator and a
refrigerant diverter valve control;
[0013] FIG. 4 is a schematic diagram of a dryer with an external warm up evaporator and a
warm air supply control;
[0014] FIG. 5 is a schematic representation of a dryer with an air economizer;
[0015] FIG. 6 is a schematic diagram of a dryer with an air economizer and a refrigerant
subcooler;
[0016] FIG. 7 is a schematic diagram of a dryer with a heat pipe air economizer and a
refrigerant subcooler;
[0017] FIG. 8 is a schematic diagram of a dryer with a heat pipe air economizer, a
refrigerant subcooler, and a refrigerant economizer;
[0018] FIG. 9 is a schematic diagram of a dryer with an alternate refrigerant subcooler
location;
[0019] FIG. 10 is a schematic diagram of a dryer with a conduction drying heat source;
[0020] FIG. 11 is a schematic diagram of a dryer with an active refrigerant expander;
[0021] FIG. 12a shows a dryer with a conventional air flow;
[0022] FIG. 12b shows a dryer in accordance with the present invention having improved
air flow;
[0023] FIG. 13a shows a dryer with a conventional air flow;
[0024] FIG. 13b shows a dryer with improved air flow;
[0025] FIG. 14 is a schematic diagram of a dryer with a heat pipe air economizer, a
refrigerant subcooler, a refrigerant economizer, and a compressor desuperheater;
[0026] FIG. 15 is a schematic diagram of a dryer with a phase change heat storage;
[0027] FIG. 16 illustrates a stationary drum with internal rotating vane assemblies;
[0028] FIG. 17 is a perspective view of an internal rotating vane assembly for use in a
drum;
[0029] FIG. 18 is a cutaway view of an internal rotating vane assembly;
[0030] FIG. 19 is a rear view of a drum showing an internal rotating vane assembly;
[0031] FIG. 20 illustrates an internal rotating vane assembly;
[0032] FIG. 21 illustrates a drum with a support ring configuration and internal rotating
vane assembly;
[0033] FIG. 22 illustrates a center support ring configuration and an internal rotating vane
assembly used therein;
[0034] FIGS. 23a and 23b show a cutaway view of a drum seal;
[0035] FIGS. 24a and 24b show a drum seal cross-section;
[0036] FIG. 25 shows a graph showing the effect of drum inlet air temperature on drum
exhaust dew point;
[0037] FIG. 26 is a graph showing the effect of drum inlet air temperature on drum exhaust
sensible heat;
[0038] FIG. 27 is a schematic diagram of a dryer having an open air circuit;
[0039] FIG. 28 is a schematic diagram of a washer having a heat pump hot water source;
[0040] FIG. 29 illustrates a drum having a rotating vane assembly and a vertical updraft;
[0041] FIG. 30 shows a conventional clothes dryer;
[0042] FIG. 31 is a schematic diagram of a heat pump dryer in accordance with the present
invention with an air cooled refrigerant subcooler;
[0043] FIG. 32 is a schematic diagram of a heat pump dryer in accordance with the present
invention with a water cooled refrigerant subcooler;
[0044] FIG. 33 illustrates the use of a water cooled dryer subcooler discharge as a hot
washwater source;
[0045] FIG. 34 illustrates the use of a water cooled dryer subcooler discharge as space heat
source;
[0046] FIG. 35 illustrates a water cooled dryer subcooler as hot washwater source for
multiple washers;
[0047] FIG. 36 is a schematic diagram of a heat pump dryer in accordance with the present
invention having a self cleaning lint filter;
[0048] FIG. 37 is a schematic diagram of a self cleaning lint filter with a J fin
configuration;
[0049] FIG. 38 is a schematic diagram of a heat pump dryer in accordance with the present
invention having fabric moisture detection and an automatic shutoff;
[0050] FIG. 39 is a schematic diagram of a heat pump dryer in accordance with the present
invention having standby moisture handling; and
[0051] FIGS 40 - 42 illustrate fabric moisture detection algorithms which can be used in
the system of FIG. 38.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Heat Pump Dryer
[0052] Inside the drum, the basic heat pump dryer functions in the same way as a
conventional dryer. Heated dry air enters the drum, extracts moisture from the clothes, and
then leaves the drum, cooler and wetter. The fundamental difference is in the way the heat
pump dryer provides the heated dry air.
[0053] Instead of continually heating room air and then venting it, the heat pump dryer
dries and warms the air from the drum exhaust, and returns it to the drum. Useful heat is
recovered and reused instead of being vented out of the building.
[0054] This is accomplished by connecting the drum exhaust back to the drum intake,
through dehumidifier means. The heat pump dryer uses a closed air loop, with dehumidifier
means in the flow path. The dehumidifier means removes entrained moisture from wet air
exiting the drum, reheats the air, and returns it to the drum. The drum is a rotating drum
which may be rotated by any suitable means known in the art.
[0055] With reference to Figure 1, heated dry air enters rotating drum, 10, at Point 1, and
extracts moisture from the tumbling fabric. Air then leaves the drum, 10, laden with extracted
moisture at Point 2, and enters the main blower, 12, which circulates drying air through the
drying air loop. Air leaves the main blower, 12, at Point 3, and passes through the wet air
heatsink, (heatsink), 14.
[0056] The heatsink, 14, as taught in U.S. Patent No. 4,603,489, which is incorporated by
reference herein, removes heat substantially equal to the power consumption of the heat
pump compressor, 16. In the preferred embodiment, heatsink, 14, is a simple air to air heat
exchanger that conducts heat from the drying air to the ambient air surrounding the dryer.
The drying air does not communicate with the ambient air, only heat is passed. Heatsink, 14,
is preferably cooled with fan or blower driven ambient room air. In an alternate embodiment,
the heatsink, 14, may be a liquid cooled type.
[0057] As the dryer is a closed loop design, continuous removal of heat substantially equal
to power consumption is necessary to control operating temperature. The heatsink, 14,
removes heat after it has performed useful work in the drum, a desirable feature. Alternate
approaches, as taught in prior art, remove heat from the drying air before it enters the drum,
cooling the air entering the drum, and materially compromising performance.
[0058] Drying air exits the heatsink, 14, at point 4, and enters the evaporator, 18, which
cools the air below its dew point. The moisture previously extracted from the fabric
condenses out of the drying air, is collected by drip tray, 20, and drains into collection tank,
22. In the preferred embodiment, an automatic pump, 24, pumps water from the collection
tank, 22, to an external drain connection. Pump, 24, may be controlled by any suitable
method, such as a float switch or electronic level sensor in collection tank, 22. In an alternate
embodiment, collection tank, 22, may be removable for manual emptying.
[0059] The evaporator, 18, extracts sufficient sensible heat to pull the temperature of the air
below its dew point, as well as heat of condensing of the water removed from the fabric. The
required evaporator cooling capacity is thus equal to the sum of the sensible heat and the heat
of condensing.
[0060] Drying air exits the evaporator, 18, at point 6, cool and effectively saturated
(Nominal RH = 85% ~ 90%), and enters the condenser, 26. The condenser 26, reheats the auto
its original temperature at Point 1. The air then exits the condenser, 26, and reenters the
drum, 10, at point 1, completing the cycle. The heating capacity of the condenser, 26, is equal
to the evaporator, 18, cooling capacity plus the power consumption of the heat pump
compressor, 16.
[0061] The additional heat, equal to the power consumption of compressor, 16, that is
added to the drying air by the condenser, 26, does useful work in the drum, 10, incrementally
increasing the moisture extraction rate. This heat is then removed by the heatsink, 14,
maintaining system heat balance.
Heat Pump
[0062] Referring again to Figure 1, the system heat pump operates as a dehumidifier, as
follows: Refrigerant exits the compressor, 16, as high pressure vapor, and passes to condenser
26, at point 1', where heat of condensation (of the refrigerant) is transferred away to the
drying air. The refrigerant condenses, and exits the condenser, 26, at point 2', as high
pressure liquid, and passes through receiver, 28, to thermal expansion valve (TEV), 30, which
reduces the refrigerant pressure. The refrigerant exits the TEV, 30, at point 5', as a low
pressure, low quality liquid/vapor mixture, (high liquid content) and enters the evaporator.
[0063] The evaporator, 18, extracts heat of vaporization of the refrigerant from the drying
air, and boils the refrigerant to the vapor state. Slightly superheated vapor exits the
evaporator, 18, at point 7', and reenters the compressor, 16, completing the cycle.
[0064] The TEV, 30, controls the refrigerant mass flow by proportionally opening and
closing in response to system conditions. In one embodiment, it maintains a constant low
superheat, to maximize evaporator capacity while preventing liquid from entering the
compressor. A plurality of TEV and control embodiments and are discussed in the System
Controls section of this document.
[0065] Control, 32, serves several functions, such as cycle time and dryness control, also
discussed in the System Controls section of this document.
[0066] The control, 32, may be a control and monitoring system implemented using a
micro-controller, micro-computer, or the like. The control, 32, may receive input from
sensors and user input/output devices. The control, 32, may be coupled to various drier
components via control lines (not shown) for controlling the respective operations. Sensors
which may be used with the control, 32, include temperature sensors positioned at various
locations along the air supply flow path and the refrigerant flow path and moisture sensors
positioned at various locations along the air supply flow path.
Heat Pump Dryer Performance and/or Efficiency Improvements
Warmup Considerations
[0067] Textile drying occurs in three phases, Rising Rate or Warmup, Steady State, and
Falling Rate, as discussed in Appendix A: Theoretical Considerations. When the heat pump
dryer is first started, it must reach operating temperature before steady state drying rate is
achieved. In practice, the rising rate phase in a heat pump dryer can be inordinately long,
undesirably increasing the total drying time. The warmup time is a function of the mass of the
heated portions of the dryer and the wet laundry, and the available heat. It is advantageous
that this phase be as short as practical, and the dryer and the wet fabric brought to operating
temperature as rapidly as practical.
Warmup Heat
[0068] In the basic configuration, as shown in Figure 1, the heat pump is the only source of
heat. At normal operating temperatures, the heat pump supplies more heat than needed for
steady state drying, and the excess is released through the heatsink, 14. However, at low
starting temperatures, the refrigerant pressure is low, and as a result, refrigerant mass flow is
low, the heat pump consumes very little power, and supplies very little heat. This causes slow
warmup, and increases the overall drying time.
[0069] Warmup time may be reduced by the addition of a warmup heater, 34, as shown in
Figure 2, which directly heats the drying air, bringing the dryer and the laundry up to
operating temperature in a comparatively short time. In the preferred embodiment, this heater
is energized only until the dryer reaches operating temperature. The heater is preferably as
large as available power permits, because a larger heater presents a shorter warmup period. It
may be used without materially increasing overall energy consumption, because it is used for
only a short time at the beginning of each cycle.
[0070] In an another embodiment, an electric warmup heater may be incorporated in the
refrigerant piping, to either supplement or replace the warmup heater, 34, in the air loop.
Radiant or conduction heating means, discussed in the section Nonconvective Heating, may
also be used for warmup heat, either in lieu of or in conjunction with, a warmup heater in the
air loop and/or the refrigerant circuit.
Alternate Warmup Means
External Evaporator
[0071] An alternate source of warmup heat may be realized by means of an external
warmup evaporator, 36, as shown in Figure 3 and Figure 4. In both embodiments, during
warmup, refrigerant gas passes from evaporator, 18, through warmup evaporator, 36, before
entering compressor, 16. Warmup evaporator, 36, draws heat from the ambient room air,
which is transported by the heat pump to the condenser, 26. This approach supplies warmup
heat equivalent to warmup heater, 34, but takes advantage of the heat pump coefficient of
performance (C.O.P.), consuming less energy than warmup heater, 34, while providing
substantially the same quantity of warmup heat.
[0072] As shown in Figure 3, warmup heat may be controlled by means of Diverter Valve,
38, which switches warmup evaporator, 36, out of the refrigerant circuit when it is not
needed. Diverter valve 38, is preferably a simple 3 way solenoid valve that is activated by
control, 32; however, any suitable valve type may be used.
[0073] When the diverter valve, 38, is in warmup mode, point 7' is connected through the
diverter valve, 38, to point 6B', and point 6' is cut off. Refrigerant then flows from the
evaporator, 18, to the warmup evaporator, 36, at point 6A'. The warmup evaporator, 36,
transfers heat from the room air to the refrigerant. The refrigerant then exits warmup
evaporator, 36, at point 6B', passes through diverter valve, 38, to compressor, 16, suction at
point 7'.
[0074] When diverter valve, 38, is in normal steady state mode, point 7' is connected to
point 6', and point 6B' is cut off. Refrigerant exits evaporator, 18, at point 6, and passes
through diverter valve, 38, to compressor suction at point 7'. Refrigerant does not enter the
warmup evaporator 36 at point 6A' because its discharge, at point 6B', is cut off. In this
mode, refrigerant bypasses the warmup evaporator, 36, entirely.
[0075] In Figure 4, an alternate means of controlling the warmup evaporator, 36, is shown.
In this embodiment, refrigerant passes through the warmup evaporator, 36, continuously.
Warmup evaporator, 36, is enclosed in a preferably insulated housing that substantially
restricts heat transfer and natural convective airflow. When warmup heat is needed, blower,
40, is energized, preferably by control, 32, forcing ambient room air over warmup evaporator,
36. When warmup heat is not needed, blower, 40, is shut down, again preferably by control,
32, and warmup evaporator, 36, is effectively cut off.
Variable Capacity Compressor
[0076] This approach compensates for refrigerant behavior at low temperatures by
increasing the effective volumetric capacity of the compressor during warmup. With
sufficiently increased volumetric capacity, the compressor 16 will draw normal or near
normal power during warmup, and will pump heat at normal or near normal steady rate. This
will provide warmup heat and good heat pump performance during warmup. Preferably, the
compressor 16 is operated at increased capacity during warmup, and then stepped or ramped
down to normal capacity as the dryer reaches desired operating temperature. Compressor
capacity control is preferably handled by Control, shown as item 32 in Figures 1-4.
[0077] This approach is also useful in conjunction with other warmup methods, to insure
proper condensation of water extracted from the laundry during warmup. Variable capacity
may be a feature of the compressor itself; with means such as unloading cylinders, variable
stroke, or the like. Alternatively, a two speed compressor motor, with separate low and high
speed windings, may be used. A preferred method is compressor speed control via variable
frequency drive electronics.
Variable Drying Air Flowrate
[0078] This approach increases compressor power consumption by reducing the drying
loop mass airflow during warmup. This causes the evaporator saturation temperature to drop
slightly, and the condenser saturation temperature to rise, effectively increasing the AT and AP
across the compressor. This in turn reduces the compressor COP, and increases compressor
power consumption.
[0079] The increased compressor power consumption in this mode is commensurate with
that achieved using a variable speed compressor. This approach may be implemented with a
simple electronic blower speed control, or with a two speed or multispeed blower motor; less
expensive to manufacture than a variable speed compressor drive.
[0080] Variable capacity compressor means and variable airflow means may be employed
together, for combined effect. The warmup heater, 34, is not needed in embodiments with
alternate warmup means; if desired, it may be used to supplement the alternate warmup
means, and further reduce warmup time.
Air Economizer
[0081] Control, 32, has been deleted from Figure 5, and subsequent figures, for clarity.
[0082] An improved embodiment of the heat pump dryer includes an air economizer, 42, as
shown in Figure 5. In this embodiment, the air economizer, 42, is an air to air heat exchanger
which operates as follows: Wet air exits the Heatsink, 14, at point 4, and instead of passing
directly to the evaporator, 18, it first enters the air economizer, 42. Heat from the wet
airstream is transferred through the air economizer, 42, to the cold saturated air exiting the
evaporator, 18, at Point 6. The two airstreams do not communicate, only heat is transferred
between them.
[0083] The cooled wet air then exits the air economizer, 42, and enters the evaporator, 18,
at Point 5. The evaporator 18 cools the air to below dew point, as in previously discussed
embodiments. However, the economizer, 42, has extracted a significant portion of the
sensible heat in the wet air, and as a result, a larger portion of the evaporator, 18, cooling
capacity is available for condensing moisture. This benefit may manifest as a smaller
(reduced cooling capacity) less expensive evaporator, or as increased moisture condensing
rate, as desired.
[0084] Cooled saturated air then leaves the evaporator, 18, and enters the economizer, 42,
at point 6, where it receives heat from the wet air entering at point 4, as discussed above. The
warmed air then leaves the economizer, 42, and enters the condenser, 26, at point 7. The
condenser 26 reheats the air as per previously discussed embodiments, however, the entering
air is significantly warmer, and the required condenser heating capacity is reduced. This may
manifest as a smaller (reduced heating capacity) less expensive condenser, or as increased
heating rate, as desired.
[0085] The heat exchange capacity of the economizer, 42, manifests as additional effective
cooling capacity at the evaporator and additional heating capacity at the condenser, with no
additional energy consumption. For a given evaporator and condenser, the addition of the air
economizer, 42, will result in increased drying rate. If they are made smaller, the compressor,
16, may also be made smaller and less expensive, and the same drying rate will be realized,
with reduced energy consumption.
Refrigerant Subcooler
[0086] The wet air heatsink, 14, is effective as a means for removing heat from the dryer,
after the heat has done useful work. An alternate means for removing heat substantially equal
to the compressor power consumption, an improvement over the wet air heatsink, 14, is
shown in Figure 6.
[0087] In this embodiment, refrigerant exits the condenser, 26, and enters the refrigerant
subcooler, 44, at point 2'. The subcooler, 44, removes heat substantially equal to the
compressor, 16, power consumption, effectively performing the same function as the
heatsink, 14, which is not needed when subcooler, 44, is used. The heatsink, 14, is shown as
dashed lines to indicate that it is not required.
[0088] Refrigerant exits the subcooler, 44, at point 3', and passes through receiver, 28, to
TEV, 30. The TEV, 30, reduces the refrigerant pressure, as in previously discussed
embodiments. However, the subcooler, 44, has removed substantial heat from the refrigerant,
and it enters TEV, 30, at significantly lower enthalpy. Refrigerant exiting TEV, 30, and
entering evaporator, 18, at point 5' is of much lower quality (more liquid, less gas) when
subcooler, 44, is used. This materially improves the cooling capacity of evaporator, 18.
[0089] The subcooler, 44, has additional advantages over the heatsink, 14. The subcooler,
44, is preferably a refrigerant to air or refrigerant to liquid heat exchanger, as opposed to the
heatsink, 14, which is an air to air heat exchanger. Consequently the subcooler, 44, is more
effective, and may be smaller and less expensive to manufacture.
[0090] The refrigerant entering the subcooler, 44, at point 2' is substantially hotter than the
wet air entering the heatsink, 14, at point 3. Consequently the subcooler, 44, has a larger
approach (AT between the refrigerant, and the cooling fluid, e.g., room air) than does the
heatsink, 14, further improving its effectiveness, and permitting additional size reduction.
[0091] The subcooler 44 also changes the system heat balance. Normally, the condenser,
26, capacity is equal to the evaporator, 18, capacity plus the compressor, 16, power
consumption. However, since compressor, 16, power is removed by the subcooler, 44, energy
balance dictates that the condenser, 26, capacity must equal the evaporator, 18, capacity.
Saturation temperatures are reduced when the subcooler is active, evaporator capacity
increases, and condenser capacity drops, until this equilibrium is reached.
[0092] As saturation temperatures in the system are reduced when the subcooler, 44, is
active, either the evaporator, 18, superheat or the refrigerant mass flow will change
accordingly. This is dependent on TEV, 30, behavior. If the TEV, 30, is configured to
maintain constant superheat, it will increase refrigerant mass flow as needed when the
subcooler, 44, is active, This will commensurately increase heat pump capacity and drying
rate, provided loop airflow is sufficient.
[0093] If evaporator, 18, superheat is permitted to float, then it will increase when
subcooler, 44, is active. This may be advantageous in some embodiments, discussed in the
Refrigerant Economizer section of this document. When the subcooler, 44, is used, increased
refrigerant superheat at the compressor suction, point 7', causes increased superheat in the
refrigerant exiting the compressor, 16, at point 1'. This in turn reduces the condenser, 26,
effectiveness, commensurate with the reduced condenser, 26, capacity required when the
subcooler, 44, is active.
[0094] The subcooler, 44, has an additional advantage when used with the air economizer,
42. When the heatsink, 14, is used, the air economizer, 42, performance is materially reduced
because wet air entering at point 4 has been cooled by the heatsink, 14. When the subcooler,
44, is used, and the heatsink, 14, is preferably not used, and the wet air entering the
economizer, 42, is substantially warmer, substantially increasing economizer, 42,
performance.
[0095] The subcooler 44 may be configured as an air cooled heat exchanger. In the air
cooled embodiment, suitable fan or blower means are preferably included to deliver ambient
room air to the subcooler air side. The fan or blower means preferably draws room air from
the front of the dryer cabinet as close to the floor as practical, where the air is generally
coolest, and exhausts the air at the rear of the cabinet, so as to avoid discharging warm air
toward the operator, and to prevent drawing exhaust air.
[0096] Subcooler, 44, may be enclosed in a preferably insulated housing that substantially
restricts heat transfer and natural convective airflow when fan 6r blower means are not
operating, thus facilitating accurate subcooler, 44, effectiveness control, via cooling airflow
control means.
[0097] Alternatively the subcooler, 44, may be liquid cooled. In this embodiment, the
cooling media may be cold tap water. In a laundry room or laundromat venue, the heat from
the subcooler in each dryer 1002 may be used to preheat wash water for use by a washer
1000. Such a scenario is illustrated in FIGS. 33 and 35. As shown in FIG. 35, multiple
washers 1000 and dryers 1002 may be manifolded together. If desired, an optional
accumulator 1004 may be provided. Each dryer 1002 may be fitted with two common
subcooler discharge water output ports if desired. Both ports are the same, and if only one is
used, the other should be capped. They may be used together for daisy chaining the dryers
together, eliminating the need for a manifold.
[0098] Referring now to FIG. 34, the water cooled dryer subcooler discharge may be used
as a space heating source when supplied to an external radiator 1006 for space heating. If
desired, the external radiator 1006 could be used for dryer cooling.
[0099] If desired, a liquid cooled subcooler, 44, embodiment may be used with a separate
air cooled radiator to cool the liquid coolant. The radiator may be used within a unitary dryer
housing to facilitate component fit, or may be remotely located, for example on a roof, or
may provide useful space or process heat. The radiator may be used for cooling a single dryer
or a plurality of dryers.
Heat Pipe Air Economizer
[00100] An alternate embodiment of the Air Economizer, 42, is shown in Figure 7. In this
embodiment, the air economizer, 42, comprises a heat pipe assembly in two heat exchanger
sections connected by heat pipe means, designated 46 and 48, shown connected by a dashed
line representing heat flux.
[00101] This approach offers thermodynamic performance similar to the air to air
economizer, 42, shown in Figure 5, with added practical manufacturing advantages. These
advantages include the ability to install the economizer, 42, in line with the evaporator, 18,
eliminating the need for crossover air ductwork, and multiple changes of direction in the
airflow path. This embodiment presents reduced air loop pressure drop, and requires less
cabinet space.
[00102] The heat pipe air economizer, 42, operates as follows: Wet air enters the heat pipe
air economizer hot section, 46, at point 4. Heat from the wet air stream is transferred away by
the hot section of the heat pipe economizer, 46. The heat pipe transports this heat to cold
section, 48. The cooled wet air then exits the air economizer hot section, 46, and enters the
evaporator, 18, at Point 5.
[00103] The evaporator cools the air below its dew point, as in previously discussed
embodiments. However, the economizer, 42, has extracted a significant portion of the
sensible heat in the wet air, and as a result, a larger portion of the evaporator, 18, cooling
capacity is available for condensing moisture. This benefit may manifest as a smaller
(reduced capacity) evaporator, or as increased moisture condensing rate, as desired.
[00104] Cooled saturated air then leaves the evaporator, 18, and enters the heat pipe
economizer cold section, 48, at point 6, where it receives heat from the wet air entering at
point 4, via the heat pipe, as discussed above. The warmed air then leaves the heat pipe
economizer cold section, 48, and enters the condenser, 26, at point 7. The condenser, 26,
reheats the air as per previously discussed embodiments. However, the entering air is
significantly warmer, and the required condenser, 26, heating capacity is reduced. This may
manifest as a smaller (reduced capacity) condenser, 26, or as increased heating rate as
desired.
[00105] As with the air to air economizer, the heat exchange capacity of the economizer, 42,
manifests as additional cooling capacity at the evaporator, 18, and additional heating capacity
at the condenser, 26, with no additional energy consumption. If the evaporator, 18, and
condenser, 26, are not changed, then the addition of the air economizer, 42, will result in
increased drying rate. If the evaporator, 18, and condenser, 26, are made smaller, the
compressor, 16, may also be made smaller, and the same drying rate will be realized with
reduced energy consumption. In Beta level residential lab tests, the air economizer, 42,
reduced energy consumption by 10% ~ 15%.
Refrigerant Economizer
[00106] Additional operating efficiency may be realized with a refrigerant economizer, 50,
as shown in Figure 8. The refrigerant economizer (RE), comprises two sections, 52, and 54.
For clarity, the drawing shows the RE, 50, as two separate sections connected by a dashed
line representing heat flux; typically the two sections comprise a single assembly. The
preferred embodiment is a flat plate type heat exchanger, but any suitable refrigerant grade
heat exchanger, such as coaxial tube, or the like, may be used.
[00107] In operation, referencing Figure 8, refrigerant exits the subcooler, 44, at point 3',
and enters the hot section of the RE, 52. The RE hot section, 52, transfers heat away from the
refrigerant, to its cold section, 54. The refrigerant then exits the RE hot section, 52, at point 4,
and passes through the receiver, 28, to the TEV, 30.
[00108] The TEV, 30, reduces the refrigerant pressure as in previously discussed
embodiments. However, the enthalpy of the refrigerant entering the TEV, 30, is reduced, and
exits the TEV, 30 at point 5' as a lower quality mixture (more liquid, less gas) than when the
RE, 50, is not used. This increases the effective capacity of the evaporator, 18. This benefit
may manifest as a smaller (reduced capacity) evaporator, or as increased moisture condensing
rate, as desired.
[00109] In the preferred embodiment, the RE, 50, is used in conjunction with the subcooler,
44. In this configuration, heat is sequentially removed from the refrigerant in both the
subcooler, 44, and the RE, 50, reducing the enthalpy of the refrigerant entering the TEV, 30,
at point 4', further than with either component alone.
[00110] Refrigerant enters the evaporator, 18, at point 5' at reduced enthalpy, where it
extracts heat of vaporization from the wet air. The refrigerant then exits evaporator, 18, as
slightly superheated vapor, and enters the RE cold section, 54, at point 6'. In the RE cold
section, 54, the refrigerant absorbs heat conducted from the liquid refrigerant in the RE hot
section, 52, and exits the RE cold section, 54, as very superheated vapor. In Beta level lab
testing, typical superheat has been on the order of 100°F.
[0100] The high superheat substantially increases the refrigerant density at the compressor,
16, suction, point 7'. If compressor, 16, is a constant displacement type, the increased
refrigerant density at point 7' results in increased refrigerant mass flow. The high temperature
at the compressor suction, point 7', also improves compressor isentropic efficiency.
[0101] In Beta level lab testing, the refrigerant mass flow increase has been on the order of
20%. This may manifest as increased heat pump capacity, and concurrent increased drying
rate, or alternatively, a less expensive, smaller displacement compressor may be used with the
RE, 50, with no performance degradation.
[0102] The high superheat delivered by the RE, 50, permits novel control methods. It is not
necessary to maintain a margin of superheat at the evaporator, 18, discharge, point 6',
because with the RE, 50, in use, there is no risk of liquid entering the compressor at point 7'.
An alternate control algorithm that maintains constant temperature of the air exiting the
evaporator, 18, at point 6, may be used, as discussed in the Controls section of this document.
[0103] The refrigerant economizer, 50, is shown in Figure 8 with the preferred heat pipe air
economizer. It may alternately be used with an air to air economizer such as shown in Figures
5 & 6; or with no air side economizer, at some loss of performance and efficiency. The RE,
50, may also be used with the heatsink, 14, with or in lieu of the subcooler, 44.
Alternate Configuration
[0104] Figure 9 shows an alternate configuration in which the relative locations of the
subcooler, 44, and the RE, 50, are interchanged. This is generally not a preferred
embodiment, but can be advantageous if a liquid cooled subcooler, 44, is desired. The
advantage of a liquid cooled subcooler, 44, is the ability to extract more heat, especially in
hot ambient conditions. However, the refrigerant exiting a liquid cooled subcooler, 44, is
sufficiently cold as to restrict or prevent useful heat extraction by the RE, 50, in the
previously discussed embodiment of Figure 8.
[0105] The alternate embodiment of Figure 9, eliminates this limitation; the RE, 50,
receives refrigerant directly from the condenser 26, at point 2', which is sufficiently hot to
permit good RE, 50, performance, and the water cooled subcooler, 44, has sufficient
approach to permit good subcooler performance with refrigerant exiting the RE, 50, at point
3'.
Compressor Desuperheater
[0106] A compressor desuperheater, 56 may be used as shown in Figure 14 to further
increase refrigerant mass flow for a given compressor. The increased mass flow may be used
toward increased drying rate, or a smaller less expensive compressor, may be used, with no
loss in performance.
Low Temperature Drying
[0107] During steady state, increasing the drum inlet temperature does not materially affect
the drum exhaust dew point, as shown in the examples of Figure 25. However, it does
increase the drum exhaust dry bulb temperature. This introduces significant sensible heat that
must be removed by the wet air heat sink and/or the evaporator, before moisture condensation
can commence.
[0108] The sensible heat represents parasitic work that is not used for drying the clothes.
As the drum inlet dry bulb temperature rises, the sensible heat rises concurrently. For a given
evaporator size, it is possible for the sensible heat to exceed the evaporator cooling capacity,
leaving no cooling capacity for condensation of water. An example of this is shown in Figure
26. It is substantially more efficient to operate with the lowest practical level of sensible heat.
[0109] There is a lower limit to this approach. If the drum exhaust temperature is low
enough, then condensate may freeze on the evaporator surface. This has compromising
effects on air mass flow and heat transfer. During steady state, the preferred configuration
employs drum inlet air as dry as practical, and operating temperatures just high enough to
prevent freezing.
[0110] Low temperature drying reduces or eliminates warmup time, uses less energy, and is
gentler to the fabric, with no compromise in performance. This is discussed in more detail in
Appendix A; Theoretical Considerations.
Improved Airflow
Horizontal Updraft Fluidized Bed Airflow
[0111] Conventional residential dryers generally employ downdraft airflow, or airflow with
a prominent downdraft component. Most residential dryers employ a drum inlet high on the
rear bulkhead, and a drum exhaust on the front bulkhead, below the door. A small number of
residential dryers employ horizontal airflow from back to front, employing a door comprising
a downdraft perforated plenum. This design also introduces a significant downdraft
component to the airflow. Another design locates both drum inlet and exhaust on opposite
sides the rear bulkhead, with the inlet located higher on the bulkhead than the exhaust. No
dryers currently employ updraft airflow, or airflow with a significant updraft component.
[0112] Downdraft airflow is disadvantageous to tumble drying. It drives the falling fabric
downward, reducing critical falling dwell time, and compacting the falling items closer to
each other. Fabric is driven forward, as well as downward toward the drum exhaust, causing a
tendency to occlude the exhaust vent. These factors compromise performance and efficiency.
[0113] An alternate airflow path may be advantageously applied, as shown in Figure 12.
Typical conventional airflow is shown in Figure 12A. Air enters the drum near the top, at the
rear, at point 58, and travels forward and downward, exiting under the door, at point 60.
Figure 12B illustrates improved airflow, in which air enters the drum under the door, at point
58', and exits near the top of the rear bulkhead, at point 60'.
[0114] In this embodiment, the updraft component of the airflow tends to fluidize the bed;
falling fabric items are falling against the airflow rather than with it, and fall more slowly,
extending critical dwell time. Falling items tend to fluff and separate rather than aggregate,
and exposure to drying air is substantially enhanced. The effects of the horizontal component
of the airflow are substantially mitigated. Fabric items do not bunch up at the bottom front or
rear of the drum, and do not occlude the drum exhaust. This embodiment provides improved
moisture extraction and drying performance.
[0115] An alternative embodiment, comprises a drum inlet on the rear bulkhead, situated
near or at the bottom, and a front drum exhaust. The door may be constructed as a plenum,
with the front drum exhaust at or near the top of the door, or alternatively, the drum exhaust
may be in the front bulkhead, above the door. These embodiments present the same
advantageous updraft airflow, with the added benefit of more accessible lint filter location.
[0116] If the drum exhaust is in the door, the lint filter may also be located in the door,
preferably near the top, to be reached easily for removal. The filter assembly may be
configured for access from inside the door, from the top of the door, or from the outside of
the door, as desired. If the drum exhaust is in the bulkhead above the door, the filter assembly
may be configured for easy access from the front of the dryer, above the door, or from the top
of the dryer, at the front, as desired.
Vertical Updraft Fluidized Bed Airflow
[0117] Conventional commercial and industrial dryers generally employ vertical downdraft
airflow. This is believed to be a safety requirement commensurate with the use of large
electric or gas fired heaters for heating the drying air. Placing a large heater or burner directly
under a load of fabric is not intrinsically safe. Consequently, the heater is generally located
above the drum, and vertical downdraft air is employed. This approach is disadvantageous; it
drives the falling clothes down toward the bottom of the drum, compacting the falling items
and substantially reducing dwell time. The exhaust draft pulls the fabric to the bottom of the
drum, substantially occluding the drum exhaust.
[0118] The heat pump dryer does not present the intrinsic fire hazard of electric and gas
fired units, and is well suited to vertical updraft airflow. An example embodiment that may
be advantageously applied is shown in Figure 13. As shown in Figure 13A, in conventional
dryers, air enters the drum from the top, at point 62, and travels vertically downward, exiting
through the bottom of the drum at point 64. In the improved embodiment, shown in Figure
13B, air enters from the bottom of the drum, at point 62', and travels vertically, exiting
through the top of the drum, at point 64'.
[0119] This embodiment presents substantially improved tumbling action; longer falling
dwell time, and improved separation of the fabric items, with commensurate improved
exposure to drying air. Drum exhaust occlusion is eliminated, and drying airflow is
substantially enhanced. Moisture extraction and drying performance may be substantially
improved with this embodiment.
Nonconvective Heating
[0120] During steady state convective drying, used by all conventional tumble dryers, and
by heat pump dryer embodiments previously discussed in this document, the overall core
fabric temperature will not exceed the wet bulb temperature of the air in the drum. This
phenomenon is not affected by the dry bulb temperature of the air entering the drum, as
discussed in the above section, Low Temperature Drying.
[0121] Nonconvective heat sources do not suffer this limitation, and present effective and
novel methods for enhancing dryer performance. These methods are capable of achieving
fabric temperature and drum exhaust dew point substantially higher than convective heating,
thus reducing warmup time, increasing drying rate, and improving efficiency.
Electric Nonconvective Heating
[0122] In one embodiment, radiant heat means may be placed so as to directly heat the
fabric, for example in the door, facing rearward toward the drum interior. This approach is
effective, but consumes additional energy. An alternate approach employs electric resistance
heaters attached to a portion of the drum wall, also effective, but also consumes additional
energy. This latter approach also introduces the need for rotating electrical connections, or a
stationary drum, as discussed in the next section of this document.
Heat Pump Nonconvective Heating
[0123] In a preferred embodiment, conductive heating means are implemented, as shown in
Figure 10, comprising a heated drum wall, 66, that directly heats the fabric via conduction.
The drum wall, 66, includes a refrigerant heat exchanger, of any suitable construction, over a
suitable portion of its circumference.
[0124] At any given time during normal tumbling, a portion of the fabric items are falling,
a portion are being lifted by the drum vanes, and a portion of the items are resting in a dense
pile at the bottom of the drum. In the preferred embodiment, the portion of the drum
circumference that is heated corresponds with the portion of the drum circumference that is
occupied by fallen fabric during tumbling. This is typically the bottom third of the drum
circumference.
[0125] In one embodiment, serpentine tubing may be bonded to the heated portion of the
drum wall, 66, by welding, soldering, or other suitable means. Alternatively, the heated
portion of drum wall, 66, may include integrated flow channels, of the type commonly used
in small refrigerator evaporators. The drum wall exterior is preferably insulated to minimize
heat loss.
[0126] In operation, high pressure superheated refrigerant exits the compressor, 16, at point
1', and enters the drum wall, 66, heating the drum wall, 66, and conducting heat to the fabric
resting on the bottom of the drum. The fabric temperature is thus raised above the wet bulb
temperature of the surrounding air, substantially increasing the moisture extraction rate.
[0127] In the preferred embodiment, the drum wall heat exchanger, 66, substantially
desuperheats the refrigerant, but does not condense it. This permits simpler, less expensive,
drum wall design, and provides ample heat for substantially increased drying rate. The nearly
saturated refrigerant then exits the drum wall, 66, at point 1A' and enters the condenser, 16.
[0128] The remaining portion of the refrigerant cycle is effectively similar to previously
discussed embodiments, except that the heating capacity of condenser, 16, is reduced by the
heating capacity of drum wall, 66. This is not a disadvantage, as the total heat applied to the
drum is the sum of the heat supplied by the condenser, 16, and the drum wall, 66.
[0129] In this embodiment, the drying air entering the drum, 10, at point 1, is slightly
cooler than in embodiments not using heated drum wall, 66. This air functions primarily as a
carrier to remove extracted moisture from the drum, and need only be hotter than the wet
bulb temperature exiting the drum, nominally equivalent to the surface temperature of the
fabric. Performance using heated drum wall, 66, will be substantially improved over
convection heated embodiments.
[0130] If the refrigerant economizer, 50, is used with the heated drum wall, the resulting
increase in compressor discharge superheat will increase the available heat at the drum wall,
further increasing the moisture extraction rate in the drum.
Rotating Drum
[0131] In a variation of this embodiment, the entire rotating drum circumference may be
heated, and preferably with insulated exterior. Refrigerant may be coupled to the drum wall
heat exchanger through rotating fittings. Alternatively, electric drum wall heat may be
similarly implemented with electric heaters on the drum wall, and slip rings for the electrical
connections.
Stationary Drum, Rotating Vane Cage
[0132] The fundamental purpose of drum rotation is to tumble the fabric being dried.
Tumbling is an essential and integral function of forced convection drying. Tumbling
fluidizes the bed, and circulates the fabric items. The fabric is exposed to drying air primarily
while it is falling.
[0133] The drum wall itself does not contribute materially to tumbling; this is the function
of the lifting vanes, which are attached to the drum wall. As the drum and vanes rotate, when
the vanes are below the horizontal centerline of the drum, their incident angle is upward, and
they catch fabric items and lift them. When the vanes are sufficiently above the horizontal
center line that their incident angle is downward, the fabric items slip off, and fall toward the
bottom of the drum.
[0134] This occurs near, but not at, top dead center. The rotational velocity imparted to the
fabric by the vanes, causes the fabric to fall in a slight arc, such that it tends to fall primarily
through the vertical centerline of the drum. If the drum did not have vanes, the fabric would
slip along the drum wall without significant lifting, and tumbling effect would be reduced to
negligibility.
[0135] To facilitate a heated drum wall in a practical manufacturable manner, it is
advantageous to couple the heat exchanger (HX) means to the refrigerant piping circuit,
without rotating slip joints or the like. In a novel preferred embodiment, the drum does not
rotate. This permits simple and low cost serpentine tubing or other suitable HX means to be
attached directly to the drum wall, and coupled to the refrigerant piping by conventional
means, known in the HVAC industry, such as soldering, brazing, or the like. Alternatively,
the heated portion of drum wall may include integrated flow channels, commonly used in
small refrigerator evaporators.
[0136] In a preferred embodiment, shown in Figures 16 - 19, tumbling is accomplished by
independently rotating a group of vanes 68, inside a stationary drum, 70. These vanes, 68, are
preferably supported by annular rings, 72 at the front, and 74 at the rear, of the drum, 70. The
rings and vanes together form a cage that fits snugly inside the drum and is rotated by a
suitable driving means, such as an electric motor.
[0137] The inside diameter of the front ring, 72, is large enough to provide access clearance
for loading and unloading the laundry, with suitable door means. The front ring, 72, may be
supported by rollers, 76, in Figure 18, which bear on the inside surface of the stationary
drum, 70. The rear ring, 74, may be formed as a perforated disk to facilitate supporting with
an axle shaft. In the latter perforated embodiment, the perforations permit drying air to pass
through the disk.
[0138] The axle shaft, not shown, passes through the rear wall of the stationary drum, and
may be attached to a suitable drive pulley or sprocket, 78, as shown in Figure 19. Pulley or
sprocket 78, may be coupled via belt or chain, 80, to a drive motor, 82. The shaft is
preferably supported by suitable bearing means in the rear drum wall. A suitable shaft seal is
preferably provided at the bearing location to prevent air leakage.
[0139] In a variation of this embodiment, one or both rings, 72 & 74, fit snugly inside the
drum, and may be fabricated from or covered with a low friction material, such as UHMW
polyethylene or Teflon, such as is currently used in the supporting drum glides in many
conventional residential dryers. Alternatively, the low friction material may be applied to the
inside surface of the drum, along the glide path of the rings.
[0140] In another alternate embodiment, the vane cage may fully be cantilevered to the rear
axle shaft, eliminating the need for rollers, 76, or glides at the front.
[0141] These embodiments have the added advantage of eliminating drum rim seals. No
moving seal is required at the front of the drum, which is effectively sealed by the door
gasket; the rear requires only a simple conventional shaft seal.
[0142] In an alternate embodiment, shown in Figures 21 & 22, the stationary drum, 70, is
comprised of two half shells, 70A & 70S, with a slot around the centerline. The front half
shell preferably includes an opening on its end wall (not shown) for loading and unloading
laundry, with suitable door means. A single ring, 84, fits between the drum shells, 70A &
70B, and supports each vane, 68, at its center. The ring, 84, may be primarily inside the drum
as shown in Figure 21, primarily outside the drum, or may be double layered, bearing on both
the inside and outside surfaces of the drum, with integral edge grooves, in which the open
ends of each drum shell ride.
[0143] At least a portion of ring, 68, is preferably exposed through the slot between the
drum half shells, 70A & 70B, and a drive belt, 80, may be wrapped around it to provide
rotation, with suitable driving means, such as an electric motor, 82. The ring, 84, may include
supporting rollers or bearing balls, riding inside and/or outside the drum wall. Alternatively,
the ring, 84, may include glide strips or bands of Teflon or UHMW polyethylene, or other
suitable low friction bearing material, such as is used to support the drum in many
conventional residential dryers.
[0144] Suitable sealing means, such as the drum sealing method discussed in the Drum
Sealing section of this document, are preferably provided at the interfaces between the ring,
84, and the drum shells, 70A, & 70B.
[0145] The vanes, 68, are preferably tapered, thick at the root, and thin at the distal edges,
and forward curved where they contact the drum wall. The vanes or the leading edges are
preferably made from a flexible, low friction material, such as UHMW polyethylene, Teflon,
or other suitable material, and may include suitable internal structural means as needed.
[0146] The vanes, 68, preferably have sufficient resilience and travel at their leading edges
to maintain contact with the drum wall, and absorb drum shape tolerance and runout, such as
that commonly found in consumer grade dryers. As the vane cage rotates, the vanes, 68,
travel under the fabric items at the bottom of the drum, and lift them to the top or nearly to
the top, where they are permitted to fall, thus facilitating tumbling action in the stationary
drum, 70.
[0147] Although unlikely, it is conceivable that an article of clothing may become caught
between the drum wall and a vane, 68. To address this, the vane cage assembly may be of
slightly smaller diameter than the drum. In this embodiment, the vane cage is positioned
slightly below the axial center of the drum, such that vanes contact the drum wall firmly at
the bottom, and begin to separate from the drum wall as they approach the top of the drum.
Figure 20 illustrates the preferred swept volume, 86, of the rotating vanes.
[0148] As the vanes 68 approach the top of the drum 70, they separate from the drum wall
freeing any clothing caught between the wall and a vane, 68, and permitting it to drop to the
bottom. In the preferred embodiment, the maximum clearance between the vanes, 68, and the
drum wall is approximately /4" to 1" at the top of the drum 70.
[0149] An alternate embodiment comprises electric heat means or refrigerant heat
exchanger means on the rear and/or front drum bulkheads, which are typically stationary in
residential dryers. This is less effective than heating the bottom of the drum circumference,
but may be less expensive to manufacture.
[0150] In a more effective variation of a heated bulkhead embodiment, the rear bulkhead
may be heated, and the drum tilted back, for example 30° ~ 45° from horizontal, thus
improving overall contact between the laundry and the heated rear bulkhead.
Stationary Drum, Commercial Dryers
[0151] Large conventional commercial dryers, typically with capacities of 50 pounds or
more, employ vertical airflow. These dryers have a stationary drum in which an inner basket
rotates. The inner basket is perforated over its entire cylinder wall. The lifter vanes are
attached to the inner basket. The outer drum includes an opening at the top and bottom, each
of which generally extends from front to back. These openings are sufficiently wide to permit
adequate airflow, typically 10% ~ 15% of the drum circumference. Heated air typically enters
the top opening, passes through the perforated rotating inner basket, and wet air exits through
the bottom opening.
[0152] To facilitate a heated drum wall in this type of dryer, the inner perforated basket
may be eliminated, and a vane cage, similar to that discussed in the previous section, may be
used. An schematic example of this is shown in Figure 29, which also illustrates preferred
updraft airflow. In the preferred updraft embodiment, heated air, 88, enters the bottom
opening and wet air, 90, exits through the top opening.
[0153] To support the heavy loads encountered in commercial dryers, the vane cage is
preferably of high structural strength and stiffness. The rear ring may be formed as a solid
disk, and the front ring may be formed as a ring with a large inside diameter to accommodate
the door. This will provide good structural integrity, and permit unimpeded vertical airflow.
[0154] As the vanes, 68, are in resilient contact with the drum wall, they may undesirably
expand into the top, 92, and/or bottom, 94, airflow openings in the stationary drum, and
become lodged against the far edge of each opening. To prevent this, and to prevent the
laundry from entering the airflow openings, the stationary drum wall may be formed of an
effectively contiguous material, such as sheet metal, and perforated in the area of each
airflow opening, 92 & 94, preferably at the top and bottom of the drum 70. Laundry and
vanes can pass cleanly over the perforated area.
Heated Drum Cool Down
[0155] The heat pump dryer generally does not require a cool down period; the fabric is
generally cool enough to handle at the end of a drying cycle, when the dryer is operating in
the preferred low temperature range. However, conduction heating sources, e.g., heated drum
wall means, preferably operate at temperatures exceeding 140° F, and cool down means are
preferred for safe and comfortable unloading and reloading of the dryer without a lengthy
cool down period.
[0156] In a simple embodiment, the cool down cycle is a control function. At the end of the
drying cycle, the control means may open the TEV, 30, permitting high pressure refrigerant
to rapidly expand and cool. This will effectively cool the accessible surfaces of the drum wall
to a safe temperature.
[0157] In situations where time is critical, such as commercial operations, a more rapid
cool down may be advantageously achieved with an alternate embodiment. This embodiment
includes valve means, preferably of the electric solenoid type, such as those used in reversible
residential HVAC heat pumps.
[0158] When the drying cycle ends, valve means are activated, preferably by control, 32,
redirecting the flow of refrigerant. In the redirected mode, low pressure refrigerant enters the
drum wall from the TEV, 30, and the drum wall effectively becomes the evaporator. During
this mode, the main blower may be shut down, effectively cutting off the condenser, and
permitting the subcooler to condense refrigerant, removing heat from the system.
[0159] This embodiment effectively chills the drum wall, providing very rapid cool down.
This mode will generally be needed for a very short time at the end of each drying cycle.
When the dryer is sufficiently cooled, the system may be shut down, and the diverter valve
returned to normal mode.
[0160] Another alternate embodiment includes valve means to configure both the
condenser and the drum wall to act as evaporators, cooling both the drum wall, and the
airstream, thus removing heat from the dryer and the fabric via the subcooler. In this
embodiment, during cool down mode, the heat released via the subcooler equals the heat
removed plus the power consumption. To accommodate this, the compressor may be operated
at reduced capacity, via speed control, or the like.
[0161] Alternatively, the subcooler capacity may be larger than necessary for normal
drying, and modulated as necessary to control drying temperature, by means discussed in the
System Controls section of this document. In cool down mode, the subcooler may then be
operated at full capacity, sufficient to remove the heat equal to the power consumption, as
well as cool the drum and fabric.
Drum Sealing
[0162] Drum sealing is an important aspect of heat pump dryer design. Minor air leaks
around the drum, generally unimportant in conventional dryers, can materially degrade heat
pump dryer performance. Room air leaking into the drum can reduce the drying air
temperature and raise the humidity, compromising moisture extraction. Air leaking from the
drum into the surrounding room can cause excessive heat loss, and undesirably raise room
humidity.
[0163] A preferred embodiment for typical residential heat pump dryers, with rotating
drums and stationary bulkheads, is shown in Figures 23 and 24. This embodiment comprises
integral flanges, 96, incorporated in the front and rear bulkheads, parallel with the drum wall,
98. Only rear bulkhead, 100, is shown. Drum wall, 98, includes a sealing area, 102, front and
rear, which may be of the same diameter as the drum, or may be stepped to a slightly smaller
diameter than the drum, as shown.
[0164] An elastomeric seal member, 104, is preferably interposed between the flange, 96,
and the drum wall seal area, 102. Seal member, 104, is of a 'D' cross section or other
suitable profile, with sufficient resilience and travel to absorb drum shape tolerance and
runout, commonly found in consumer grade dryers, while maintaining good sealing contact
with the drum wall sealing area, 102.
[0165] Seal member, 104, is preferably bonded to flange, 96, with double faced tape, self
adhesive backing, or other suitable means, and drum wall sealing area, 102, is then the sliding
seal surface. In the preferred embodiment, the seal assembly is not weight bearing, and the
drum is rotationally supported by separate means. Reduced friction means, such as Teflon or
UHMW polyethylene tape, may be bonded to the drum wall sealing area, 102, along the
contact line of the sealing member, 104, to reduce rotational drag.
[0166] Alternatively, seal member 104, may be bonded to drum sealing area, 102, with 'D'
profile facing outwards, in orientation opposite that shown, and flange, 96, is then the sliding
sealing surface. Reduced friction means may be bonded to flange, 96, to reduce drag. A
single sealing member, 104, or a plurality of sealing members may be used, as desired.
[0167] In an alternate embodiment, not shown, flange 96, may be eliminated, and drum
wall sealing area may be folded inward, 90° to drum wall, 98, and parallel with bulkhead,
100, forming an inner flange on drum wall, 98. Sealing member 104, may then be bonded to
the drum wall sealing area, or to the mating portion of the bulkhead, 100, forming a face
seal.
[0168] The location of blower, 12, is generally not critical, however it is preferably located
at the drum exhaust, to induce slight negative air pressure in the drum, preventing any
moisture or heat from escaping into the room.
System Controls
[0169] Control, 32, shown in Figures 1-4, serves several functions. In the most basic
embodiment, the control, 32, may comprise a simple timer, preferably electronic, that starts
the system and stops it after a preselected running time elapses. It preferably performs startup
sequentially, to minimize electrical surge loads and to establish drum rotation and airflow
before starting the compressor, 16.
[0170] In the preferred sequence, the control, 32, first starts the blower, 12, then starts the
drum, 10, rotation, and then starts the compressor, 16. The time between these events is
preferably sufficient for the blower to reach full speed before starting the compressor, e.g., 1 -
2 seconds, however any desirable delay may be employed. In another alternate embodiment,
the drum, 10, and blower, 12, may be driven by the same motor. Additional functionality of
control, 32, may include temperature and/or humidity control, safety limits, cycle selection,
and the like.
[0171] In the preferred embodiment, fabric dryness is monitored by control, 32, and the
system is shut down automatically when desired dryness is achieved; this is discussed in the
Dryness Control section of this document. Such a system is shown in FIG. 38. As shown
therein a drum air in, humidity sensor 1040 and a drum air in temperature sensor 1042 are
provided at the inlet to the drying drum 10. Also provided are a drum air out temperature
sensor 1044 and a drum air outlet humidity sensor 1046 at the outlet of the drum 10. Each of
the sensors 1040, 1042, 1044 , and 1046 provides a signal to the control 32 which determines
the fabric moisture and provides a signal to shutoff the dryer when a desired moisture is
attained. Logic flow charts of sample algorithms which may be used in such a system are
shown in FIGS. 40 - 42. FIG. 40 shows a differential temperature algorithm. FIG. 41 shows
a differential humidity algorithm. FIG. 42 shows a combined differential humidity and
temperature algorithm. The intent of all these algorithms is to recognize when the aggregate
fabric load is dry, and then check for individual wet items. Typically, an isolated item will be
wet when the rest of the load is dry, because it was wrapped in another item or is of
substantially heavier fabric than the rest of the load. In this instance, as the wet time tumbles
past the drum exhaust, the temperature will briefly fall and the relative humidity will briefly
rise. Either may reset dwell time.
[0172] While FIG. 38 shows both temperature and relative humidity sensors, both are not
required. Optionally, the dwell timer may also be reset by a dT/dt or dRH/dt spike. For
example, if differential temperature is used as shown in FIG. 40, a single relative humidity
sensor at the drum exhaust or outlet may also be employed. If, during the dwell time, there is
a rapid rise in exhaust relative humidity, faster than a threshold slope, this will also reset the
dwell timer.
Temperature Control
[0173] It is desirable to maintain relatively constant operating temperature during drying.
In the preferred embodiment, the evaporator saturation temperature is kept as low as practical
without causing ice accumulation. The dryer temperature may preferably be controlled by
modulating the effectiveness of the wet air heatsink, 14, and/or the subcooler, 44, as desired.
[0174] It is desirable to accomplish temperature control with as little hysteresis as practical,
particularly when the subcooler, 44, and refrigerant economizer, 50, are both used.
[0175] The refrigerant economizer, 50, transfers more heat when the subcooler, 44, is cut
off. When the subcooler, 44, is switched on or off, e.g. via fan cycling, the TEV, 30,
typically requires 15 ~30 seconds to equalize; an inefficient transitional state. Proportional
control is thus preferable to on/off control for this embodiment, and is advantageous for all
embodiments.
[0176] FIG. 31 illustrates a further embodiment of a heat pump dryer system in accordance
with the present invention wherein a temperature sensor 1010 is placed just outside the hot air
inlet to the drying drum 10. The sensor 1010 provides a signal representative of the
temperature at the inlet of the drying drum 10 to a temperature control 1012. The
temperature control 1012 generates a fan speed control signal which is used to operate a
subcooler fan or blower 1014. The fan or blower 1014 utilizes cooling air from a room or
other suitable source to air cool the subcooler 44.
[0177] FIG. 32 illustrates still another embodiment of a heat pump dryer system in
accordance with the present invention where the temperature sensor 1010 provides a signal
representative of the temperature at the inlet of the drying drum 10 to a temperature control
1012. The temperature control 1012 generates a cooling water control signal which is fed to
a cooling water control valve 1016. The valve 1016 receives cooling water from a facility
water supply or other suitable source and supplies the cooling water to a water cooled
subcooler 44. As shown in FIG. 32, the outlet of the water cooled subcooler may be
connected to a discharge water accumulator 1018. If desired, water in the accumulator 1018
may be discharged to a heat load such as a washer as shown in FIG. 35.
Heatsink
[0178] In embodiments using the wet air heatsink, the heatsink, 14, may be modulated by
means of active mechanical dampers; varying the volume flow of cooling room airflow over
the heatsink, or varying heatsink bypass in the drying air loop.
[0179] Alternatively, modulation may be accomplished by cycling the heatsink fan, or
preferably, by varying the heatsink fan speed. Variable fan speed, will advantageously reduce
or eliminate parasitic temperature hysteresis that is typically encountered with fan cycling.
[0180] In fan controlled embodiments, the heatsink, 14, may be enclosed in a preferably
insulated housing that substantially restricts heat transfer and natural convective airflow when
the fan or blower is not operating, thus facilitating accurate control of heatsink, 14,
effectiveness with variable cooling airflow means.
Subcooler
[0181] In embodiments using the subcooler, modulation may be accomplished with diverter
valve means, that switch the subcooler in or out of the refrigerant circuit, as desired, in a
manner similar to the warmup evaporator diverter valve, shown as item 38, in Figure 3.
[0182] Alternatively, the subcooler fan may be cycled as needed to modulate the subcooler.
In the preferred embodiment, subcooler modulation is accomplished with variable fan speed,
which achieves modulation without the hysteresis introduced by fan cycling.
[0183] In fan controlled embodiments, the subcooler, 44 may be enclosed in a preferably
insulated housing that substantially restricts heat transfer and natural convective airflow when
the fan or blower is not operating, thus facilitating accurate control of subcooler, 44,
effectiveness with variable cooling airflow means.
Thermal Expansion Valve
[0184] The thermal expansion valve (TEV), 30, may be configured to maintain constant or
near constant superheat at the evaporator discharge. This may be accomplished with a simple
mechanical TEV, 30, of the sensing bulb type, or preferably with a stepper motor type valve,
under proportional or PID control.
[0185] In an alternate embodiment, the TEV, 30, may be configured to ignore evaporator
superheat, and seek to maintain constant air temperature exiting the evaporator. This is the
most direct method of maintaining evaporator air temperature as low as practical without
freezing.
[0186] This latter approach ignores evaporator superheat, which may in practice approach
zero (saturated vapor). This will not compromise performance, or introduce risk of liquid
entering the compressor, if it is used with the refrigerant economizer, 50. The refrigerant
economizer, 50, introduces substantial superheat at the compressor suction, and saturated
vapor at the evaporator discharge will have no undesirable effect.
[0187] A constant pressure valve, capillary tube or other suitable expansion means, may be
used in place of the TEV, 30, if desired.
[0188] Refrigerant receiver, 28, is preferred, offering modest performance improvement,
but it is not essential, and may be eliminated if desired, slightly reducing manufacturing cost.
Dryness Control
[0189] Dryness may be monitored with classical electronic means that measure the
electrical resistance of the fabric, via metallic fingers, that are mounted in the bulkhead or
over insulated vanes. While this method works well, and has evolved into an industry
standard, it does have its disadvantages. The placement of the metal strips is critical, else the
wet clothes may not make the connection often enough to satisfy the sensor logic. In addition,
it relies heavily on perfect tumbling of the clothes. If the clothes become wound up, as is
common with large items such as sheets, or if a few pieces of clothing simply stay toward the
back or front of the dryer, the metal strips may not sense individual wet items, and the dryer
may stop short of appropriate dryness.
[0190] In a preferred embodiment, the mixing ratio of drying air entering and exiting the
drum may be monitored. When the mixing ratio difference across the drum is within a desired
tolerance, such as 5 grams of water per kilogram of dry air, the run may be continued for a
suitable dwell time, such as 5 minutes, and stopped. This 5 minute dwell accommodates
fabric windup and/or hidden small items. If such is the case, these items intermittently
separate during the 5 minute dwell, and the mixing ratio of the air leaving the drum briefly
rises, restarting the dwell timer means. However, if after five minutes, there is no transient
rise in the drum exhaust mixing ratio, the laundry is considered dry. This method has
generally proved accurate to 0.2 pounds of bone dry (2.5 % of dry weight).
Open Loop Air Circuit
[0191] An alternative to the closed air loop embodiments discussed in previous sections of
this document is shown in Figure 27. The blower, 12, may be located as shown, or may be
located at the drum, 10, exhaust, point 3, to induce slight negative static pressure in the drum,
as discussed in the section Drum Sealing.
[0192] In this embodiment, room air is drawn into the condenser, 26, at point 1, where it is
heated. The heated room air exits the condenser, 26, enters the drum 10 at point 2, and
extracts moisture from the fabric. The air then exits the drum 10 cooler and wetter, and enters
the evaporator, 18, at point 3, which extracts heat from the air. The wet air leaves the
evaporator, 18, at point 4, passes through the blower 12, to external vent means at point 5,
where it is preferably vented to the outdoors.
[0193] In this embodiment, the condenser, 26, performs the function of the heater in a
conventional dryer, with substantially less power consumption, taking advantage of the heat
pump COP. The evaporator, 18, does not condense all of the moisture in the drum exhaust. It
removes sufficient heat for heating incoming room air at the condenser, 26. Moisture not
condensed out is vented outdoors with the exhaust air. Subcooler, 44, and wet air heatsink,
14, are not required, as heat substantially equal to the compressor, 16, power consumption is
vented from the system with the exhaust air.
[0194] In an alternate embodiment, the evaporator, 18, capacity may be sufficient to
condense substantially all the moisture from the exhaust air, permitting the exhaust air to be
vented into the room, and not requiring outdoor venting means. In this embodiment,
subcooler, 44, may be used to removed heat substantially equivalent to the compressor, 16,
power consumption. Exhaust air may be used to cool the subcooler, 44, eliminating the need
for a separate subcooler, 44, fan or blower.
[0195] In a variation of a fully condensing embodiment, wet air heatsink, 14, may be used,
alone, or with subcooler, 44, to remove heat substantially equivalent to the compressor, 16,
power consumption. In this embodiment, the evaporator, 18, capacity may be reduced, such
that the combined heat transfer capacity of the heatsink, 14, and the evaporator, 18, is
sufficient to remove sensible heat and condense substantially all the moisture in the exhaust
air.
[0196] An air to air economizer or heat pipe economizer may be employed, with hot
section at the system exhaust, point 5, and cold section at the system intake, point 1, for
improved efficiency.
[0197] Refrigerant economizer, 50, may be applied to any of the above embodiments to
improve heat pump performance.
[0198] This embodiment draws room air, and like conventional dryers, it is unable to
reduce the partial pressure of water vapor in the drying air, as discussed in Appendix A:
Theoretical Considerations. It presents the following advantages and tradeoffs:
Advantages
Substantially Reduced Manufacturing Cost
No Heat Pipe
Subcooler Not Required
Smaller Heat Pump
Tradeoffs
Drying Air Discharge
Outdoor Vent Required for Most Venues
Chemical Vapors In Exhaust
Dryer Sheets
Wash Additives
Slower, Drying Time Commensurate With Conventional Dryers
Additional Process Enhancements
Warmup Heat Storage
[0199] Warmup time and warmup energy consumption may be reduced by storing waste
heat generated during operation. While the preferred media is a blend of paraffins and/or
other waxes, this may be accomplished with any heat storage media of sufficient capacity,
that is suitable for the operating temperature range.
[0200] One embodiment is shown in Figure 15, in which a phase change heat exchanger,
106, contains phase change media and suitable support structure, interposed in the wet air
discharge from the drum, 10. Said support structure is configured to present sufficient surface
area exposure of the media to the drum exhaust air, as well as maintain the form factor of the
media while in the liquid state.
[0201] While the dryer is at steady state operating temperature, the phase change media
absorbs heat from the drum exhaust air, effectively performing the function of the wet air
heatsink, 14. Air exiting the phase change heat exchanger, 106, is sufficiently cooled to limit
the effectiveness of the heatsink, 14. This continues until the phase change media is
substantially melted, and cannot absorb any more heat. At this point, the heatsink, 14
performs its usual function of removing heat from the dryer for the remainder of the cycle.
Heatsink, 14, may be shut down, preferably by control, 32, as discussed in previous sections
of this document, until heat storage media becomes saturated.
[0202] When the dryer is started for a subsequent drying cycle, if it is cold, or if it is not
fully warmed up, the phase change heat exchanger, 106, will heat the drum exhaust air,
contributing warmup heat to the dryer. When the media is fully frozen, and cannot supply any
more heat, or if the dryer reaches proper temperature before this occurs, the media ceases to
contribute heat, and the cycle continues normally. During the steady state period, the media is
reheated.
[0203] This approach shortens warmup time with no added energy consumption,
effectively reducing drying time and energy consumption per load.
[0204] An alternate embodiment employs heat storage media in the refrigerant circuit (not
shown). In the preferred refrigerant circuit embodiment, the heat storage media is located
between the condenser, 26, and subcooler, 44, at point 2'. In an alternative refrigerant circuit
embodiment, the heat storage media may be integrated with the subcooler, 44, or may be
located between subcooler, 44, and refrigerant economizer, 52, at point 3'.
[0205] In this latter embodiment, the subcooler, 44, may be shut down, preferably by the
system controls, until the heat storage media is saturated. The temperature of saturated heat
storage media will lower than that of the preferred refrigerant circuit embodiment, concurrent
with heat removed by the subcooler, 44, during steady state.
[0206] In the preferred refrigerant circuit embodiment, phase change media absorbs heat
from the refrigerant exiting the condenser, 26, cooling the refrigerant, and serving the
function of subcooler, 44. While the media is absorbing heat, it cools the refrigerant
sufficiently to limit the effectiveness of the subcooler, 44. When the phase change media
becomes saturated, i.e. when it is fully melted, and can no longer absorb heat, the subcooler,
44, performs its usual function of removing heat from the dryer for the remainder of the
cycle. Subcooler, 44, may be shut down, preferably by control, 32, as discussed in previous
sections of this document, until heat storage media becomes saturated.
[0207] When the dryer is started for a subsequent drying cycle, if it is cold, or if it is not
fully warmed up, the phase change media will heat the refrigerant entering the economizer,
50, contributing warmup heat to the dryer. The economizer, 50, conducts this heat directly to
the compressor suction, increasing suction gas density, and refrigerant mass flow. This
compounds the effect of the phase change media; the heat pump operates at useful
effectiveness before reaching operating temperature, further reducing warmup time.
[0208] When the media is fully frozen, and cannot supply any more heat, or if the dryer
reaches proper temperature before this occurs, the media ceases to contribute heat, and the
cycle continues normally. This approach substantially shortens warmup time without added
energy consumption, effectively reducing drying time and energy consumption per load.
Active Expander
[0209] To improve heat pump efficiency and further reduce drying energy consumption, as
shown in Figure 11, this embodiment employs an active expander, 108, in place of the TEV.
The expander, 108, serves the same function as the TEV, but instead of using irreversible
friction as the source of pressure drop, reversibly extracts energy from the refrigerant. The
preferred embodiment employs a small scroll type refrigerant compressor, operating in
reverse as an expander, and generating useful electricity. A scroll type expander will
advantageously tolerate internal vaporization of the refrigerant during expansion.
[0210] This arrangement preserves the hermetic nature of the heat pump refrigerant circuit,
and its concurrent design life and reliability. The electrical output from the expander may
sent to electronic controls that provide steady controlled electrical supply, over a range of
expander rotation speeds. The resultant clean electrical supply may be used to operate
ancillary items, such as fan and/or drum motors, or may supply a portion of the compressor
power, as desired.
Advanced Refrigerant and Equipment for Using Same
[0211] In the interest of entirely eliminating Hydrocarbons, Fluorines, and Chlorines from
the heat pump, it is advantageous to use water as the refrigerant. A heat pump system
intended for water based working fluid presents novel equipment design considerations,
which offer manufacturing advantages, as well as zero ODP, and zero Global Warming.
[0212] A heat pump system using water as the refrigerant will operate at substantially
lower pressures and higher volume flow than with conventional refrigerants. Heat pump
equipment designed for water based refrigerant will have commensurately different
requirements.
[0213] Typical system pressures in a heat pump, operating in the preferred temperature
range of a heat pump dryer, are less than ~1 PSIA on the low side, and ~10 PSIA on the high
side. Refrigerant volume flow rates are substantially higher than with conventional systems.
The compressor for the preferred embodiment is a hybrid design, resembling a high pressure
blower as much as a conventional heat pump compressor.
[0214] One embodiment of a suitable compressor is a rotary vane type, optimized to handle
deep vacuum on the low side, and high differential pressure, as compared with typical rotary
vane devices. An alternate embodiment comprises regenerative blower stages. Conventional
regenerative blowers are not capable of sufficient differential pressure for use in a heat pump,
and a modified design is necessary. One embodiment comprises a plurality of cascaded
regenerative blower stages.
[0215] The low pressure side of this system operates at a substantial vacuum with respect
to ambient atmospheric pressure. To accommodate this, suitable means to prevent air from
infiltrating the system through shaft seals, or the like, are needed. For this purpose, and for
motor cooling, the compressor block is preferably encased in a hermetic shell, similar to
conventional heat pump compressors.
[0216] In conventional systems, refrigerant soluble lubricant is used in the compressor. A
small amount invariably escapes the compressor through piston rings, scroll seals, or the like.
The escaped lubricant is permitted to circulate throughout the refrigerant circuit, and
eventually returns to the compressor at the suction side.
[0217] One compressor embodiment, for use with water refrigerant, is an oilless type,
requiring no lubricant. An alternate embodiment, which presents improved sealing and
reduced blow by qualities, incorporates a water soluble lubricant that is permitted to circulate
throughout the refrigerant circuit. The preferred lubricant will not materially compromise the
thermodynamic properties of the water refrigerant.
[0218] Water refrigerant introduces the possibility of corrosion. In the preferred
embodiment, the piping is nonmetallic, and piping corrosion is not an issue. Corrosion in the
compressor may be addressed with a plurality of methods. One embodiment employs
corrosion inhibitors in the soluble lubricant. An alternate method, which may be used with or
without corrosion inhibitors, is the use of corrosion resistant materials or platings for the
compressor wetted components.
[0219] A third embodiment comprises oxygen getter means installed in the system piping.
Such means remove entrained oxygen from the refrigerant during the first minutes or hours of
run time, mitigating or eliminating corrosion in the compressor, piping, and in all system
components that contact the refrigerant. The getter media may react with available oxygen,
converting it to an inert compound that remains captivated in the media, may catalytically
absorb it, or may use other suitable means for removing available oxygen from the system.
[0220] In a preferred hermetic embodiment, the getter means may be an ablative single use
type, that is substantially consumed in the oxygen removal process. The getter media may be
packaged in a sealed canister that is installed during system manufacture, removes available
oxygen upon first use, and becomes a permanent passive component, much like the
filter/dryer used in conventional systems.
[0221] The heat exchangers in this system will also depart from conventional heat pump
HX design. In light of the low operating pressures, and high volumetric flowrates, classical
small bore Fin and U Tube configurations will not perform properly. A preferred HX
embodiment comprises comparatively large diameter inlet and exhaust ports manifolded to a
substantial plurality of parallel flow tubes or channels. The low operating pressures will
permit very inexpensive HX designs.
[0222] The piping design will also be a departure from conventional systems. It will
preferably be of larger diameter, and may be of lighter materials, such as aluminum, PVC, or
other suitable polymer. In the preferred embodiment, PVC piping is used with solvent welded
joints, offering substantially reduced manufacturing cost over conventional systems.
[0223] Water refrigerant exhibits practical saturation pressures at temperatures typical of
air conditioning systems, and heat pump equipment using water refrigerant may be used in air
conditioning applications, as well as in the heat pump dryer.
Supplemental Features
Stationary Drum For Drying Nontumble Items Such As Sneakers
[0224] Conventional dryers often provide a removable stationary rack for drying sneakers
and the like. This rack attaches to the rear drum bulkhead, which typically does not rotate,
and to the front door frame. It's only purpose is to provide a stationary platform for items that
cannot be tumbled.
[0225] The heat pump dryer has a separate drum or vane drive that may be stopped for
drying items such as sneakers. If desired, a multilevel rack may be provided for drying large
quantities of nontumble items. This rack may simply rest inside the drum without need for
complex attachment means.
[0226] An alternate embodiment comprises a single or multilevel rack that captivates items
to be dried, so the drum or vanes may rotate without causing these wet items to tumble or fall.
In this embodiment, drum or vane rotation speed may be reduced to minimize the effects of
unbalance while providing enhanced exposure of wet items to drying air. In a stationary drum
embodiment, this type of rack may attach to the vanes, and rotate with them as an integral
unit.
Modular Heat Pump
[0227] The heat pump system may be constructed as unitary module, permitting simplified
removal for repair or replacement. A unitary module may also be advantageously connected
to an existing conventional tumble dryer, thus converting it to a heat pump dryer. In the latter
case, the module may be configured as a pedestal which the connected dryer sits upon.
Heat Pump Dryer Sheets
[0228] Dryer sheets, currently available from a number of vendors, contain a form of fabric
softener that outgases during drying, and infiltrates the fabric. These sheets are designed for
conventional dryers, and produce sufficient active vapor to maintain desired concentration, as
the drum air is continually replaced with room air.
[0229] The heat pump dryer does not dilute the air loop with room air, and dryer sheets
need not produce the quantity of active vapor necessary for use with conventional dryers. A
reduced vapor rate dryer sheet for use with heat pump dryers will exhibit performance
commensurate with conventional dryer sheets used in conventional dryers, at substantially
less cost.
[0230] In an alternate embodiment, a suitable easily accessible holder may be provided in
the heat pump dryer air loop, in which a longer life product may be placed. This product,
preferably heat or moisture activated, may outgas active vapor at a slow rate, only during
drying. It may be fabricated as a sponge, molded cake, or the like, and may be designed to
last for any desirable number of drying cycles before being replaced. The holder may be
located in the door, as part of the lint filter assembly, or any suitable location in the air loop.
Heat Pump Hot Water Source
[0231] The heat pump hot water source will generate hot water from cold, or preheat a
water heater feed stream. It may heat or preheat process water for any suitable process. It
accomplishes this by recovering and storing heat, that would otherwise be wasted, from hot
drain water, such as from a washer or washers. Heat storage is preferably accomplished with
suitable phase change media, such as paraffin or eutectic salt, allowing sequential heat
recovery and subsequent use; the heat source and the heated process need not operate
simultaneously.
[0232] The heat pump preferably uses the stored heat to raise incoming wash water, such as
cold tap water, to the proper wash temperature. The heat pump means may comprise a large
central system that collects and stores heat from a plurality of washer drains, and heats wash
water for a plurality of washers. In the preferred embodiment, the system is integrated in a
single washer, or configured as a pedestal that is placed under an existing washer.
Commercial washers are significantly shorter than their counterpart dryers, and the pedestal
may raise the washer to a more convenient loading height.
[0233] An example of the preferred embodiment is illustrated in Figure 28. In this
embodiment, a heat pump, comprising compressor 16, condenser 110, economizer 50,
receiver 28, TEV 30, and evaporator 112, is interposed between heat storage means, 114 and
116. Heat storage means 114 and 116 may comprise any suitable heat storage media; the
preferred heat storage embodiment comprises containers of suitable phase change media,
such as a paraffin or eutectic salt, or suitable blend thereof. In the preferred embodiment, heat
exchangers, 118 and 112, are integrated within the drain side heat storage media 114, and
heat exchangers, 110 and 120, are integrated within the supply side heat storage media 116.
[0234] When the washer, 124, calls for hot wash water, tap water enters the supply side
heat storage means 116, at point 1, and passes through heat exchanger means 120, integrated
within the heat storage media, which heats the tap water to desired wash temperature, as
described below. Heated wash water exits the heat storage means 116, and enters the warmup
heater, 34, at point 2. The wash water passes through warmup heater 34, and enters the
washer 124, hot water inlet, at point 3. If there is insufficient heat stored for heating incoming
cold wash water, such as during the first run of a cold start, the warmup heater 34, may be
energized to heat the wash water.
[0235] At the completion of the first or any subsequent wash cycles, the drain water leaving
the washer 124, retains substantial heat. This drain water exits the washer 124, at point 4, and
enters drain diverter valve 126. If drain water is sufficiently warm, it passes through the
diverter valve 126, and enters drain side heat storage means 114, at point 7. The drain water
then passes through heat exchanger means 118, integrated within the heat storage media.
Heat exchanger means, 118 transfers heat from the drain water to heat storage media, and the
cooled drain water exits to an external drain provision, at point 5.
[0236] The heat storage media in heat storage means 114, retains the heat transferred from
the drain water. In the preferred embodiment, this media is of the phase change type, such as
a paraffin or eutectic salt, or suitable blend thereof. The heat storage media preferably has
sufficient capacity to store the heat of one or more complete wash cycles.
[0237] The heat pump transports the heat stored in the drain side heat storage means 114,
via heat exchanger means 112, the refrigerant evaporator, to the supply side heat storage
means 116, via heat exchanger means 120, the refrigerant condenser. The supply side heat
storage media stores the pumped heat. The supply side heat storage media is preferably a
phase change media, similar to the drain side media, with a melting point commensurate with
wash temperature.
[0238] When sufficient heat is stored in the supply side media for heating wash water, the
warmup heater, 34 is no longer needed and may be shut off. Incoming cold tap water passes
through heat exchanger means, 110, which transfers heat from the heat storage means, 116, to
the incoming tap water. The tap water, thus heated to proper wash temperature, exits the
supply side heat storage means, 116, at point 2, then passes through warmup heater, 34,
unchanged if already at desired wash temperature, and enters the washer 124, hot water inlet,
at point 3.
[0239] The drain side water heat exchanger, 112 and storage means, 114, is preferably of
sufficient heat transfer capacity to recover and store drain water heat in real time. Likewise,
the supply side water heat exchanger, 120, and heat storage means, 116, is preferably of
sufficient heat transfer capacity to heat incoming tap water to wash temperature in real time.
[0240] The heat storage means are preferably insulated sufficiently to store heat for a
period of time exceeding the maximum idle time of the washer, 124, for example, overnight.
[0241] In the preferred embodiment, heat is stored on both the drain side and the supply
side. This takes advantage of the fill and drain duty cycle, which is relatively low; each
generally requiring approximately 5 minutes, and typically occurring at intervals of 15 to 20
minutes.
[0242] The heat pump is preferably of lower capacity than the heat storage means, and
operates for a period exceeding the drain and fill times and less than the interval between fill
cycles, as needed, to pump stored heat from the drain side to the supply side heat storage
means. This advantageously permits the use of a smaller, less expensive heat pump, with no
compromise in performance.
[0243] Alternatively, heat storage media may be implemented only at the drain or fill side.
In this embodiment, the heat pump is of sufficient capacity to pump heat either from the drain
water or to the wash water in real time. This embodiment permits the use of heat storage
means at either the drain or supply side and not at both, but requires a substantially larger and
more expensive heat pump.
[0244] In practice, it is common for the wash water to be hot, and the rinse water be warm
or cold. It is disadvantageous for cold drain water to pass through the drain side heat storage
means, 114. In the preferred embodiment, when the drain water temperature falls below a
preset threshold, diverter valve, 126, is activated, causing drain water to bypass the heat
storage means, 114, entirely, at point 4, and pass directly to an external drain provision, at
point 6.
[0245] As cold drain water generally follows a cold fill cycle, it is not necessary to heat the
incoming tap water for same. In the aggregate, over a sufficient plurality of wash cycles,
stored heat will generally be commensurate with needed heat.
[0246] The washer, 124, tub or drum is preferably insulated, to minimize heat loss during
the wash dwell time. Typical energy and operational cost reduction, when this system is used
with a washer or a plurality of washers, is commensurate with that of the heat pump dryer.
Appendix A: Theoretical Considerations
Three States of Drying
[0247] In convective drying, there are three discemable states in the transition from wet to
dry fabric: Warmup or Rising Rate, Steady State, and Fatting Rate.
[0248] Warmup is the first state of convective drying. In this state, the fabrics are at their
highest moisture content, and the drying air is relatively dry. At this stage, the surface
temperature of the fabric to be dried is lower than the wet bulb temperature of the drying air.
This is the driving mechanism during warmup. The wet bulb temperature of the drying air
must be reduced, and the surface temperature of the clothes must be increased. The drying air
therefore transfers heat to the clothes, and the clothes transfer moisture to the air. This
mechanism will stop when the equilibrium condition is met, i.e., when the surface
temperature of the clothes equals the wet bulb temperature.
[0249] During Steady State drying, the surface temperature of the clothes remains constant,
as does the wet bulb temperature of the air. There is a stable transfer rate of moisture from the
fabric to the air and the drum is effectively adiabatic during this time. The mechanism for
drying in Steady State is the difference in partial pressures between water in the air/fabric
boundary layer, and water in the bulk air (Discussed below in Low Temperature Drying
Mechanism). Steady State continues while the core of the wet fabric has sufficient moisture
to feed the surface at the same rate as the surface releases moisture to the air. However, at
some point there will no longer be enough moisture in the core of the fabric to sustain this,
and mass transfer will begin to slow the process down. This threshold is referred to as the
Critical Moisture Content. The Critical Moisture Content varies with the size and shape of
the laundry item, as well as the fabric itself.
[0250] Falling Rate is the last and least efficient state of drying. In this state, there is
insufficient moisture near the surface of the fabric to keep the partial pressure of water in the
air/fabric boundary layer constant. As this partial pressure decreases, the driving force behind
drying is reduced. Mass transfer is therefore the bottleneck during this state, as the drying air
can remove only the moisture on the surface. Mass transfer is the movement of moisture
through the fabric from the core to the surface, and is governed by two variables; the fabric
itself, and its internal energy. The fabric cannot be changed, so the only variable that can be
used to increase the driving force for drying is the internal energy of the clothes. It is
relatively difficult to transfer heat via convection during this state, and the drying rate
therefore falls continuously until it becomes asymptotic. This is the practical limit for
convection drying.
Low Temperature Drying Mechanism
"Equilibrium Moisture Content
In drying of solids, it is important to distinguish between hygroscopic and
non-hygroscopic materials. If a hygroscopic material is maintained in contact
with air at constant temperature and humidity until equilibrium is reached, the
material will attain a definite moisture content. This moisture is termed the
equilibrium moisture content for the specified conditions. Equilibrium
moisture may be absorbed as a surface film or condensed in the fine
capillaries of the solid at reduced pressure, and its concentration will vary
with the temperature and humidity of the surrounding air. However, at low
temperatures, e.g., 60° F to 12(f F, a plot of equilibrium moisture content vs
per cent relative humidity is essentially independent of temperature. At zero
humidity the equilibrium moisture content of all materials is zero." (Perry &
Chilton, Chemical Engineers' Handbook, Fifth Edition: 20-12. McGraw-Hill,
1973)
[0251] The above excerpt illustrates the theory behind drying clothes at relatively low
temperatures. The mechanism for this drying is not the boiling of water, but rather the
tendency of two bodies, with differing moisture content, to reach equilibrium. This is the
same mechanism that dries the skin in cold weather. It is driven by the difference between the
partial pressures of water vapor in the drying medium (in this case, air) and on the surface of
the moist fabric.
[0252] The surface of the clothes during steady state drying is always at the wet bulb
temperature of the surrounding air (the core of the fabric will be measurably colder than the
surface). At the boundary layer between the clothes and the air, the temperature of both the
clothes and the surrounding film of air will therefore be the wet bulb temperature. Since the
clothes are wet, the surrounding film of air will be saturated (100% RH). There is a specific
and known partial pressure of water vapor in this film of air which corresponds to 100% RH
at the temperature of the boundary layer. The relative humidity of the bulk drying air is not
100%, it is in fact much lower. This corresponds to a lower partial pressure of water vapor in
the bulk air.
[0253] This difference in partial pressures causes the water vapor in the boundary layer to
migrate into the bulk air. This loss of water vapor is immediately replenished by the surface
of the clothes, drying the clothes and remoistening the boundary layer air. This mechanism
relates to a drying rate in the following equation:
Drying Rate = ht 'A Ap
[0254] In this equation, ht is the total heat transfer coefficient between the moist fabric and
the convective drying medium (in this case, air). A is the total aggregate surface area of the
moist fabric exposed to the drying medium. A is dependent on the size of the load, the size of
the drying drum, and the speed at which the drum spins. Ap is the partial pressure difference
discussed earlier.
[0255] This equation shows that for a given load of laundry in a drum of a given size, the
only variable that directly controls drying rate is the difference in partial pressures (Ap).
There are two ways of increasing Ap, and therefore the drying rate; increasing the saturated
partial pressure of water vapor at the boundary layer, or decreasing the partial pressure of
water vapor in the bulk air.
[0256] A conventional dryer is incapable of decreasing the partial pressure of water vapor
in the bulk air, because it draws room air, and the partial pressure of water vapor in air does
not measurably change with the dry bulb temperature. Instead, a conventional dryer uses heat
to increase the surface temperature of the clothes, which in turn increases the partial pressure
of water vapor at the boundary layer.
[0257] The heat pump dryer partially uses heat in the same manner, however it also uses
the evaporator coil to reduce the overall moisture content of the bulk air that enters the drum.
This combined capability of reducing the partial pressure of water in the bulk air and
increasing the partial pressure of the water in the boundary layer allows the heat pump dryer
to dry faster at lower drum inlet temperatures.
Standby Moisture Handling
[0258] During long down times, the moisture in the drying air loop may become stale, and
may support bacterial growth. This may be treated in a variety of ways as outlined below.
The treatment ways may be used individually or in combination with each other.
1: Drying out the dryer
[0259] A: Active System, using one or two very small fans, perhaps 20 watts each. These
may be configured to purge the drying air loop between runs. One fan and a vent or one
suction fan and one discharge fan may be used. They may be very low airflow, as there is no
need to purge quickly. They may cycle briefly after each run, or may be programmed to cycle
after a predetermined period of idle time.
[0260] FIG. 39 illustrates such an active system. As shown therein, an input purge fan
1060 may be used to provide air to the drying air loop. The output of the fan 1060 may be
connected to the drying air loop via a check valve or damper 1062. The system may also
include an exhaust purge fan 1064 that is connected to the drying air loop via a check valve
or damper 1066.
[0261] The discharge vent for this approach may be active, either solenoid or motor
operated. It may also be a simple one way shutter, similar in construction to venetion blinds.
If placed at the main blower suction, and biased to close when the main blower is running, it
will close during normal dryer operation. When he purge fan is running, it will open to allow
purge air to exit. The entire configuration may be reversed, with the damper on the main
blower discharge, allowing air to enter only, and the purge fan exhausting air.
[0262] B: Passive System. Humidity sensitive semiporous membrane material, such as
those made by Mitsubishi, and used in refrigerator crisper drawers, may be used in the drying
air loop. If desired, two ports may be created to permit cross flow through the drying air loop.
The ports may be located at a point of relatively low pressure relative to the room ambient to
mitigate stress on the membrane.
[0263] Referring now to FIG. 39, in a preferred embodiment, a membrane 1068 may be
placed at a dry section of the drying air loop, such as the drum inlet. The membrane 1068
will then close in response to the humidity. When the dryer is idle, and the humidity in the
loop equalizes, the membrane 1068 will open, permitting slow migration of moisture out of
the loop. Alternatively, one membrane 1068, and one small purge fan 1064 may be used.
2: Antibacterial
[0264] A: Ultraviolet Lamps in the evaporator section will greatly mitigate bacterial growth
in the loop, and will help freshen the clothes. Small diameter fluorescent UV lamps placed
across the evaporator so the light penetrates the space between the fins will be very effective.
FIG. 39 illustrates a plurality of ultraviolet light sources 1070 placed adjacent a self cleaning
lint trapping evaporator 18.
[0265] B: Ozone Generator means may also be used to retard bacterial growth and render
the clothing smelling very fresh. This may run during idle time and/or during drying time. It
may be desirable to have a two power setting, so the ozinator runs at low power during idle,
and higher power during drying.
[0266] C: Dryer Sheets: The closed loop system requires less treatment vapor, and less
than 54 of a standard sheet seems to provide very good results, and leaves the dryer smelling
nice for at least a day or two.
D: Integrated Lint Filter & Dryer Sheet
[0267] A lint filter fabricated of very small pore open cell foam, or corrugated paper based
media may be treated with fabric softener chemistry similar to that used in disposable dryer
sheets. The filter may be mounted in a suitable disposable or reusable frame, that fits specific
models of dryer and replaces the existing lint filter. The filter may be of sufficient surface
area (eg via corrugations) so as to permit running a plurality of loads before discarding it.
[0268] In a heat pump dryer, because much less lint is generated, and the closed loop
configuration of the heat pump dryer consumes less softener chemistry, facilitating the use of
the filter/softener embodiment for numerous loads. This type of filter in a heat pump dryer
may have a design life 10 or more loads, permitting nominal weekly replacement.
Integrated Self Cleaning Lint Removal
[0269] Dryer design to date has sought to prevent lint from reaching the evaporator. Lint
will tend to stick to the wet evaporator surfaces and ultimately occlude it. However, as a
relatively small amount of lint is produced by this dryer, the evaporator might be designed to
attract lint, eliminating the need for a lint filter entirely. FIG. 36 illustrates such an
embodiment.
[0270] The evaporator 18 may have a plurality of fins (not shown) spaced sufficiently to
allow modest lint buildup on the fins without compromising airflow. Convoluted fins will
tend to attract more lint than flat fins. Some portion of the lint will wash down with the
condensate that drips into the collection tray 20.
[0271] The evaporator 18 may be self cleaning. As shown in FIG. 36, a spray or wash of
condensate water from the sump 22 may be pumped by a lint flush pump 1020 over the
evaporator fins, washing all remaining lint into the condensate tray 20. Lint may then be
pumped out of the dryer by drain pump 1022 with the condensate drain discharge. This
washdown may be done at the conclusion of each drying cycle, or at programmed intervals
during drying. For example, a lint flush control 1024 may be provided. It may be advantages
to circulate washdown water continuously during drying; the impact of this on condensing
performance must be evaluated.
[0272] Further, a self cleaning lint trap 1026 may be provided in the air pathway. The trap
1026 may positioned between the blower 12 and the evaporator 18, which evaporator may be
self-cleaning if desired. Water from the sump 22 may be provided to the lint trap 1026 by the
pump 1020. Water containing lint may be collected by the tray 1028 and drained to the sump
22.
[0273] Moderate water pressure may be used to facilitate lint removal from the fins,
however a high volume flush will likely yield better results. Proper manifold design with at
least one discharge nozzle between each pair of fins, combined with fin design, will
thoroughly flush the interfin gaps. A larger sump that holds sufficient water for washdown
may be desired.
[0274] The manifold may be a single pass across the top of the evaporator, or may employ
a plurality of passes across the evaporator at several heights. It may be constructed of an
additional tubing circuit, similar to the refrigerant circuits, perforated between the fins. If
numerous small perforations are used, such that a plurality occurs in each gap between fins, it
will not be necessary to precisely align the perforations between the fins. This will permit
integrating the washdown circuit into the evaporator during its manufacture.
[0275] The addition of an additional tubing circuit for washdown will render the overall
evaporator 18 slightly larger. This will provide slightly increase fin surface and proper
effectiveness with moderate lint loading.
[0276] This function may be achieved with a condensate diverter valve that selects either
the condensate drain hose, or the washdown nozzles. However, it is simpler, more reliable,
and likely of similar cost to simply use two pumps in the sump, one for drain discharge, and
the other for evaporator washdown. This also permits optimization of each pump for its
specific purpose.
[0277] The heat pipe assembly may also tend to get wet, and/or attract lint, and may need
to be washed down as well.
JFins
[0278] As shown in FIG. 37, interdigitated J fins 1030 may be used in a dedicated prefilter
design. Each pair of adjacent J fins 1030 has a flush water spray nozzle 1034 which is
provided with lint filter flush water via line 1032. Drying loop air 1034 passes between
adjacent ones of the J fins 1030. Water is collected in the tray 1036 and drained to the sump
22. This design takes advantage of the velocity inertia of the lint particles, which will not
negotiate the J turns and will tend to impinge on the fins. This might be done in an evaporator
design, but as higher fin density is needed for proper evaporator capacity than is needed for
lint trapping, a J fin evaporator may impose an undesirable air pressure drop.
Porous Fins
[0279] Hollow porous fins, fabricated of sintered microporous material or microperforated
sheet may offer an effective wet down approach. Washdown water is fed to the hollow
plenum formed by each fin, at moderate pressure, and oozes through the pores, maintaining a
wet external surface, and good drainage downflow. This offers the advantage of completely
wetted trap surfaces, and even wetting. This will help prevent lint from sticking to unwetted
fin surface, and resisting removal. It will also likely require less washdown volume flow.
[0280] Although it is a bit complex, porous fins might also be applied directly to an
evaporator.
Spray or Fog
[0281] This method will tend to humidify the drum exhaust air. This air is already quite
wet, and the humidification effect of spray or fog may not be significant.
[0282] Spray, and to a greater extent fog, will trap lint in the air stream, but provision must
be made to drive the lint ladent spray/fog to drain properly, and not carry lint in the airstream
to the evaporator.
[0283] A spray or fog in combination with J fins, immediately downstream of the spray/fog
source, may work well. It may be desirable to chill the J fins. This can be done with the
refrigerant circuit, and will simply precool the air, without adding additional heat pump work.
[0284] It is apparent that there has been provided in accordance with the present invention
a heat pump clothes dryer which fully satisfies the objects, means, and advantages set forth
hereinbefore. While the present invention has been described in the context of specific
embodiments thereof, other alternatives, modifications, and variations will become apparent
to those skilled in the art having read the foregoing description. Accordingly, it is intended to
embrace those alternatives, modifications, and variations as fall within the broad scope of the
appended claims.






We claim:
1. A drying apparatus comprising:
a housing;
a drying chamber mounted in the housing for containing articles to be dried, said drying chamber including an air inlet where drying air is delivered to said drying chamber and an air outlet where drying air leaves said drying chamber;
an air flow path connecting said air inlet to said air outlet to form a substantially closed drying loop;
a blower arranged to circulate air in said drying loop and through said drying chamber;
a heat pump comprising:
a refrigerant loop;
a compressor arranged to circulate refrigerant in said refrigerant loop under pressure, said compressor having a power consumption;
a first heat exchanger connected to said refrigerant loop and arranged in said drying loop so that heat from drying air leaving said drying chamber is transferred to said refrigerant, reducing the temperature of said drying air to below dew point so that moisture extracted from articles in said drying chamber condenses out of said drying air;

a valve in said refrigerant loop, said valve controlling the flow of refrigerant into said first heat exchanger;
a second heat exchanger connected to said refrigerant loop and arranged in said drying loop between said first heat exchanger and said drying chamber so that heat from said refrigerant is transferred to said drying air entering said drying chamber; and
a refrigerant sub cooler in said refrigerant loop and connected between a discharge of said second heat exchanger and said valve, said refrigerant sub cooler comprising a third heat exchanger configured to extract a quantity of heat from refrigerant leaving said second heat exchanger, the quantity of heat extracted being modulated to be substantially equal to the power consumption of said compressor, said quantity of heat being removed from said refrigerant after said refrigerant has warmed said drying air, wherein said quantity of heat is removed from said drying apparatus.
2. The drying apparatus as claimed in claim 1, wherein said third
heat exchanger is a refrigerant to air heat exchanger or a refrigerant to
liquid heat exchanger.
3. The drying apparatus as claimed in claim 1, wherein said third heat
exchanger is a refrigerant to liquid heat exchanger constructed to
transfer heat from said refrigerant to a liquid coolant and said drying

apparatus includes a coolant flow path for delivering liquid coolant to said third heat exchanger from a source outside said drying apparatus and returning said liquid coolant to a location outside said drying apparatus.
4. The drying apparatus as claimed in claim 1, comprising a heat
transfer device including a heat absorbing component arranged in said
drying loop to extract heat from said drying air entering said first heat
exchanger, a heat emitting component arranged in said drying loop to
return at least a portion of said heat to said drying air leaving said first
heat exchanger and a heat transfer path from said heat absorbing
component to said heat emitting component.
5. The drying apparatus as claimed in claim 1, wherein said compressor is arranged to pressurize refrigerant leaving said first heat exchanger and deliver said pressurized refrigerant to said second heat exchanger, said drying apparatus comprising a refrigerant to refrigerant heat exchanger arranged to transfer heat from refrigerant leaving said second heat exchanger to refrigerant leaving said first heat exchanger before said refrigerant is pressurized by said compressor.
6. The drying apparatus as claimed in claim 1, wherein said drying chamber is mounted for rotation about an axis within said cabinet and said chamber includes vanes or baffles for tumbling articles placed in the

chamber, said air inlet communicating with said drying chamber at a position below said axis, whereby said drying air enters said drying chamber in an upward direction.
7. The drying apparatus as claimed in claim 1, wherein said first heat
exchanger is an evaporator which receives refrigerant from said thermal
expansion valve and said second heat exchanger is a condenser which
receives refrigerant from said compressor.
8. The drying apparatus as claimed in claim 4, wherein said heat transfer device is a heat pipe.
9. The drying apparatus as claimed in claim 1, wherein said valve is a thermal expansion valve configured to maintain the refrigerant leaving said first heat exchanger at constant or near constant superheat.
10. The drying apparatus as claimed in claim 9, wherein said thermal
expansion valve is electronically controlled.
11. The drying apparatus as claimed in claim 1, wherein said drying
chamber includes an inside surface, at least a portion of which is heated.

12. The drying apparatus as claimed in claim 11, wherein said inside
surface is heated by a refrigerant heat exchanger connected to said
refrigerant loop, whereby heat from said refrigerant is transferred to said
inside surface.
13. The drying apparatus as claimed in claim 12, wherein said
refrigerant heat exchanger is integral to said drying chamber.
14. The drying apparatus as claimed in claim 12, wherein said
refrigerant heat exchanger comprises tubing forming a portion of said
refrigerant loop bonded to a surface of said drying chamber.
15. The drying apparatus as claimed in claim 1, wherein the drying chamber comprises a cylindrical drum fixedly mounted within said housing and having an inside surface, said drying apparatus comprising a plurality of vanes arranged to rotate within said drum in contact with or in close proximity to said inside surface.
16. The drying apparatus as claimed in claim 12, wherein said refrigerant heat exchanger is connected to said refrigerant loop between said compressor and said second heat exchanger.

17. The drying apparatus as claimed in claim 1, wherein said heat pump includes an active expander.
18. The drying apparatus as claimed in claim 1, wherein said active expander comprises a scroll type refrigerant compressor.
19. The drying apparatus as claimed in claim 1, comprising sensors arranged to detect a moisture content of said articles and a controller arranged to control said drying apparatus as a function of the detected moisture content.
20. The drying apparatus as claimed in claim 19, wherein said
sensors include at least one of a humidity sensor at said air inlet, a
temperature sensor at said air inlet, a humidity sensor at said air outlet
and a temperature sensor at said air outlet.
21. The drying apparatus as claimed in claim 1, wherein the quantity
of energy extracted at said refrigerant sub cooler is modulated according
to a measured system parameter which varies with the power
consumption of the compressor.






Documents:

1638-delnp-2006-1-Claims (18-11-2009).pdf

1638-delnp-2006-1-Correspondence-Others (18-11-2009).pdf

1638-delnp-2006-1-Form-3 (18-11-2009).pdf

1638-delnp-2006-1-Form-5 (18-11-2009).pdf

1638-delnp-2006-1-GPA (18-11-2009).pdf

1638-DELNP-2006-Abstract (12-11-2009).pdf

1638-delnp-2006-Abstract-(14-10-2014).pdf

1638-delnp-2006-abstract.pdf

1638-delnp-2006-assignments.pdf

1638-DELNP-2006-Claims (12-11-2009).pdf

1638-delnp-2006-claims.pdf

1638-delnp-2006-Correspondence Others-(14-10-2014).pdf

1638-DELNP-2006-Correspondence-Others (03-11-2009).pdf

1638-DELNP-2006-Correspondence-Others (10-11-2009).pdf

1638-DELNP-2006-Correspondence-Others (12-11-2009).pdf

1638-DELNP-2006-Correspondence-Others (17-11-2009).pdf

1638-delnp-2006-Correspondence-Others (18-11-2009).pdf

1638-delnp-2006-Correspondence-Others (19-11-2009).pdf

1638-delnp-2006-correspondence-others.pdf

1638-delnp-2006-description (complete).pdf

1638-DELNP-2006-Drawings (10-11-2009).pdf

1638-delnp-2006-drawings.pdf

1638-delnp-2006-Form-1 (19-11-2009).pdf

1638-delnp-2006-form-1.pdf

1638-delnp-2006-Form-2-(14-10-2014).pdf

1638-delnp-2006-form-2.pdf

1638-DELNP-2006-Form-3 (17-11-2009).pdf

1638-delnp-2006-form-3.pdf

1638-delnp-2006-Form-5 (19-11-2009).pdf

1638-delnp-2006-Form-5-(14-10-2014).pdf

1638-delnp-2006-form-5.pdf

1638-delnp-2006-GPA-(14-10-2014).pdf

1638-delnp-2006-pct-101.pdf

1638-delnp-2006-pct-105.pdf

1638-delnp-2006-pct-110.pdf

1638-delnp-2006-pct-111.pdf

1638-delnp-2006-pct-202.pdf

1638-delnp-2006-pct-210.pdf

1638-delnp-2006-pct-220.pdf

1638-delnp-2006-pct-237.pdf

1638-delnp-2006-pct-301.pdf

1638-delnp-2006-pct-306.pdf

1638-delnp-2006-pct-308.pdf

1638-delnp-2006-pct-311.pdf

1638-delnp-2006-pct-318.pdf

1638-delnp-2006-pct-332.pdf

1638-delnp-2006-pct-401.pdf

1638-delnp-2006-pct-402.pdf

1638-delnp-2006-pct-409.pdf

1638-delnp-2006-pct-416.pdf

1638-delnp-2006-Petition-137 (18-11-2009).pdf


« Previous Patent
Next Patent »
Patent Number 263424
Indian Patent Application Number 1638/DELNP/2006
PG Journal Number 44/2014
Publication Date 31-Oct-2014
Grant Date 28-Oct-2014
Date of Filing 27-Mar-2006
Name of Patentee SELF PROPELLED RESEARCH AND DEVELOPMENT SPECIALISTS, LLC
Applicant Address 479 SILVER LANE, EAST HARTFORD, CT 06118, UNITED STATES OF AMERICA
Inventors:
# Inventor's Name Inventor's Address
1 GOLDBERG, MICHAEL 176 STANLEY DRIVE, GLASTONBURY, CT 06033, UNITED STATES OF AMERICA
2 TRUMAN, JAMES, C. 56 CRANE HILL ROAD, STORRS, CT 06268, UNITED STATES OF AMERICA
3 KNIFFIN, ALEXANDER, B. 70 FOREST STREET, EAST HARTFORD, CT 06118, UNITED STATES OF AMERICA
PCT International Classification Number D06F58/00
PCT International Application Number PCT/US2004/031624
PCT International Filing date 2004-09-23
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/507466 2003-09-29 U.S.A.
2 10/949139 2004-09-23 U.S.A.