Patent Publication Number: US-10774463-B2

Title: Dryer appliance

Description:
FIELD OF THE INVENTION 
     The present subject matter relates generally to dryer appliances, and more particularly to dryer appliances that utilize a heat pump. 
     BACKGROUND OF THE INVENTION 
     A conventional appliance for drying articles such as a clothes dryer (or laundry dryer) for drying clothing articles typically includes a cabinet having a rotating drum for tumbling clothes and laundry articles therein. One or more heating elements heat air prior to the air entering the drum, and the warm air is circulated through the drum as the clothes are tumbled to remove moisture from laundry articles in the drum. Gas or electric heating elements may be used to heat the air that is circulated through the drum. 
     In a known operation, ambient air from outside is drawn into the cabinet and passed through the heater before being fed to the drum. Moisture from the clothing is transferred to the air passing through the drum. Typically, this moisture laden air is then transported away from the dryer by, for example, a duct leading outside of the structure or room where the dryer is placed. The exhausted air removes moisture from the dryer and the clothes are dried as the process is continued by drawing in more ambient air. 
     Unfortunately, for the conventional dryer described above, the exhausted air is still relatively warm while the ambient air drawn into the dryer must be heated. This process is relatively inefficient because heat energy in the exhausted air is lost and additional energy must be provided to heat more ambient air. More specifically, the ambient air drawn into the dryer is heated to promote the liberation of the moisture out of the laundry. This air, containing moisture from the laundry, is then exhausted into the environment along with much of the heat energy that was used to raise its temperature from ambient conditions. 
     One alternative to a conventional dryer as described above is a heat pump dryer. More specifically, a heat pump dryer uses a refrigerant cycle to both provide hot air to the dryer and to condense water vapor in air coming from the dryer. Since the moisture content in the air from the dryer is reduced by condensation over the evaporator, this same air can be reheated again using the condenser and then passed through the dryer again to remove more moisture. Moreover, since the air is recycled through the dryer in a closed loop rather than being ejected to the environment, the heat pump dryer can be more efficient to operate than the traditional dryer described above. In addition, the heating source provided by the sealed refrigerant system of a heat pump dryer can be more efficient than a gas or electric heater implemented in the conventional dryer. 
     During operation of a typical heat pump dryer, the dryer consumes power. The dryer system will heat continuously during operation. If the amount of power consumed is greater than the rate of heat transfer to the surroundings, the system will heat up. Excessive heat can lead to reduced performance and reliability. More particularly, as air circulates, the temperature of the air within the sealed loop increases. Similarly, the thermal load to the sealed refrigerant system increases. Simply put, the excess heat must go somewhere. In some instances, the thermal load may be reduced or offset by venting hot air into the ambient environment around the dryer appliance to dissipate the excess heat, e.g., to the laundry room, via air exchange. However, this may result in undesired increases in ambient temperature within a living space. 
     Accordingly, a heat pump dryer appliance having improved thermal energy management would be advantageous. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides a heat pump dryer appliance configured to reject excess compressor capacity, e.g., thermal energy, to water such as condensate water, as well as related methods of operating a heat pump dryer appliance to reject excess compressor capacity to water. Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one exemplary aspect of the present disclosure, a dryer appliance is provided. The dryer appliance may include a cabinet with a drum rotatably mounted within the cabinet. The drum defines a chamber for the receipt of articles for drying. The dryer appliance also includes a sealed refrigerant circuit in thermal communication with the chamber and a condensation tank configured to receive condensate from an evaporator of the sealed refrigerant circuit. The condensate is selectively in thermal communication with a condenser of the sealed refrigerant circuit. 
     In another exemplary aspect of the present disclosure, a method of operating a dryer appliance is provided. The method may include providing a flow of air from a condenser of a sealed refrigerant circuit to a chamber defined within a drum of the dryer appliance. The method may also include discharging air from the chamber to an evaporator of the sealed refrigerant circuit. The method may further include circulating air from the evaporator to the condenser. When the air passes over and around the evaporator, moisture from the air condenses at the evaporator forming a condensate. The method may include transferring thermal energy from the condenser of the sealed refrigerant circuit to the condensate. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures. 
         FIG. 1  provides a perspective view of a dryer appliance in accordance with exemplary embodiments of the present disclosure. 
         FIG. 2  provides a perspective view of the example dryer appliance of  FIG. 1  with portions of a cabinet of the dryer appliance removed to reveal certain components of the dryer appliance. 
         FIG. 3  provides a schematic diagram of an exemplary heat pump dryer appliance according to one or more embodiments of the present disclosure. 
         FIG. 4  provides a perspective view of a condensation tank as may be incorporated in a heat pump dryer appliance according to one or more embodiments of the present disclosure. 
         FIG. 5  provides a section view of the condensation tank of  FIG. 4  according to at least one embodiment of the present disclosure. 
         FIG. 6  provides a section view of the condensation tank of  FIG. 4  according to at least one additional embodiment of the present disclosure. 
         FIG. 7  provides a section view of the condensation tank of  FIG. 4  according to at least one additional embodiment of the present disclosure. 
         FIG. 8  provides a flow chart of an exemplary method of operating a heat pump dryer appliance according to one or more embodiments of the present disclosure. 
         FIG. 9  provides a perspective view of a condenser in thermal communication with condensate of a heat pump dryer appliance according to one or more embodiments of the present disclosure. 
         FIG. 10  provides a perspective view of a condenser in thermal communication with condensate of a heat pump dryer appliance according to one or more additional embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Turning now to the figures,  FIG. 1  provides dryer appliance  10  according to exemplary embodiments of the present disclosure.  FIG. 2  provides another perspective view of dryer appliance  10  with a portion of a cabinet or housing  12  of dryer appliance  10  removed in order to show certain components of dryer appliance  10 . Dryer appliance  10  generally defines a vertical direction V, a lateral direction L, and a transverse direction T, each of which is mutually perpendicular, such that an orthogonal coordinate system is defined. While described in the context of a specific embodiment of dryer appliance  10 , using the teachings disclosed herein, it will be understood that dryer appliance  10  is provided by way of example only. Other dryer appliances having different appearances and different features may also be utilized with the present subject matter as well. 
     Cabinet  12  includes a front panel  14 , a rear panel  16 , a pair of side panels  18  and  20  spaced apart from each other by front and rear panels  14  and  16 , a bottom panel  22 , and a top cover  24 . Within cabinet  12 , an interior volume  29  is defined. A drum or container  26  is mounted for rotation about a substantially horizontal axis within the interior volume  29 . Drum  26  defines a chamber  25  for receipt of articles of clothing for tumbling and/or drying. Drum  26  extends between a front portion  37  and a back portion  38 . Drum  26  also includes a back or rear wall  34 , e.g., at back portion  38  of drum  26 . A supply duct  41  may be mounted to rear wall  34  and receives heated air that has been heated by a heating assembly or system  40 . 
     As used herein, the terms “clothing” or “articles” includes but need not be limited to fabrics, textiles, garments, linens, papers, or other items from which the extraction of moisture is desirable. Furthermore, the term “load” or “laundry load” refers to the combination of clothing that may be washed together in a washing machine or dried together in a dryer appliance  10  (e.g., clothes dryer) and may include a mixture of different or similar articles of clothing of different or similar types and kinds of fabrics, textiles, garments and linens within a particular laundering process. 
     A motor  31  is provided in some embodiments to rotate drum  26  about the horizontal axis, e.g., via a pulley and a belt (not pictured). Drum  26  is generally cylindrical in shape, having an outer cylindrical wall  28  and a front flange or wall  30  that defines an opening  32  of drum  26 , e.g., at front portion  37  of drum  26 , for loading and unloading of articles into and out of chamber  25  of drum  26 . A plurality of lifters or baffles  27  are provided within chamber  25  of drum  26  to lift articles therein and then allow such articles to tumble back to a bottom of drum  26  as drum  26  rotates. Baffles  27  may be mounted to drum  26  such that baffles  27  rotate with drum  26  during operation of dryer appliance  10 . 
     Drum  26  includes a rear wall  34  rotatably supported within main housing  12  by a suitable fixed bearing. Rear wall  34  can be fixed or can be rotatable. Rear wall  34  may include, for instance, a plurality of holes that receive hot air that has been heated by a heat pump or refrigerant based heating system  40 , as will be described further below. Moisture laden, heated air is drawn from drum  26  by an air handler, such as blower fan  48 , which generates a negative air pressure within drum  26 . The air passes through a duct  44  enclosing screen filter  46 , which traps lint particles. As the air passes from blower fan  48 , it enters a duct  50  and then is passed into heating system  40 . Heating system  40  may be or include a heat pump including a sealed refrigerant circuit, as described in more detail below with reference to  FIG. 3 . Heated air (with a lower moisture content than was received from drum  26 ), exits heating system  40  and returns to drum  26  by duct  41 . After the clothing articles have been dried, they are removed from the drum  26  via opening  32 . A door  33  provides for closing or accessing drum  26  through opening  32 . 
     In some embodiments, one or more selector inputs  70 , such as knobs, buttons, touchscreen interfaces, etc., may be provided or mounted on a cabinet  12  (e.g., on a backsplash  71 ) and are in operable communication (e.g., electrically coupled or coupled through a wireless network band) with a processing device or controller  56 . Controller  56  may also be provided in operable communication with motor  31 , blower  48 , or heating system  40 . In turn, signals generated in controller  56  direct operation of motor  31 , blower  48 , or heating system  40  in response to the position of inputs  70 . As used herein, “processing device” or “controller” may refer to one or more microprocessors, microcontroller, ASICS, or semiconductor devices and is not restricted necessarily to a single element. The controller  56  may be programmed to operate dryer appliance  10  by executing instructions stored in memory (e.g., non-transitory media). The controller  56  may include, or be associated with, one or more memory elements such as RAM, ROM, or electrically erasable, programmable read only memory (EEPROM). For example, the instructions may be software or any set of instructions that when executed by the processing device, cause the processing device to perform operations. It should be noted that controllers as disclosed herein are capable of and may be operable to perform any methods and associated method steps as disclosed herein. For example, in some embodiments, methods disclosed herein may be embodied in programming instructions stored in the memory and executed by the controller. 
     Turning now to  FIG. 3 , a schematic view of exemplary embodiments of dryer appliance  10  is provided. It is understood that, except as otherwise indicated, dryer appliance  10  in  FIG. 3  may include some or all of the features described above with respect to  FIGS. 1 and 2 . 
     In operation, one or more laundry articles  1000  may be placed within the chamber  25  of drum  26 . Hot dry air  150  may be supplied to chamber  25  whereby moisture within laundry articles  1000  may be drawn from the laundry articles  1000  by evaporation, such that warm saturated air  152  may flow from chamber  25  to an evaporator  102  of the heating system  40 . As air passes across evaporator  102 , the temperature of the air is reduced through heat exchange with refrigerant that is vaporized within, for example, coils or tubing of evaporator  102 . This vaporization process absorbs both the sensible and the latent heat from the moisture laden air—thereby reducing its temperature. As a result, moisture in the air is condensed and such condensate may be drained from heating assembly  40 , e.g., using line  124  which may be seen in  FIG. 2 . 
     Air passing over evaporator  102  becomes drier and cooler than when it was received from drum  26  of dryer appliance  10 . As shown, cool dry air  154  from evaporator  102  is subsequently caused to flow across a condenser  108  (e.g., across coils or tubing), which condenses refrigerant therein. The refrigerant enters condenser  108  in a gaseous state at a relatively high temperature compared to the air  154  from evaporator  102 . As a result, heat energy is transferred to the air at the condenser section  108 , thereby elevating its temperature and providing warm dry air  150  for resupply to the drum  26  of dryer appliance  10 . The warm dry air  150  passes over and around laundry articles  1000  within the chamber  25  of the drum  26 , such that warm saturated air  152  is generated, as mentioned above. Because the air is recycled through drum  26  and heating system  40 , dryer appliance  10  can have a much greater efficiency than traditional clothes dryers where warm, moisture laden air is exhausted to the environment. 
     As shown, some embodiments of heating system  40  include a compressor  104  that pressurizes refrigerant (i.e., increases the pressure of the refrigerant) supplied by suction line  110  and generally motivates refrigerant through the sealed refrigerant circuit of heating system  40 . Compressor  104  may be in operable communication with controller  56  and is generally designed to pressurize a gas phase refrigerant. Accordingly, in order to avoid damage, refrigerant in suction line  110  is supplied to the compressor  104  in a gas phase from the evaporator section  102 . The pressurization of the refrigerant with compressor  104  increases the temperature of the refrigerant (e.g., as directed by controller  56 ). The compressed refrigerant is fed from compressor  104  to condenser  108  through line  112 . As relatively cool air from the evaporator  102  is passed over the condenser  108 , the refrigerant is cooled and its temperature is lowered as heat is transferred to the air for supply to drum  26 . 
     Upon exiting condenser  108 , the refrigerant is fed through line  114  to an expansion device  106 . Although only one expansion device  106  is shown, such is by way of example only. It is understood that multiple such devices may be used. In the illustrated example, expansion device  106  is a thermal expansion valve. In additional embodiments, any other suitable expansion device, such as a capillary tube, may be used as well as or instead of the thermal expansion valve  106 . Expansion device  106  lowers the pressure of the refrigerant and controls the amount of refrigerant that is allowed to enter the evaporator  102  via line  116 . Importantly, the flow of liquid refrigerant into evaporator  102  is limited by expansion device  106  in order to keep the pressure low and allow expansion of the refrigerant back into the gas phase in the evaporator  102 . The evaporation of the refrigerant in the evaporator  102  converts the refrigerant from its liquid-dominated phase to a gas phase while cooling and drying the air from drum  26 . The process is repeated as air is circulated through drum  26  and between evaporator  102  and condenser  108  while the refrigerant is cycled through the sealed refrigerant circuit, as described above. 
     In some embodiments, the compressor  104  may be a single-speed compressor. In such embodiments, the rate of heat imparted to the refrigerant by the compressor  104  will remain relatively constant throughout operation of the dryer appliance  10 . During operation, and as the process described above is repeated, the moisture content of the articles  1000  decreases. Thus, the capacity of the articles  1000  to absorb heat decreases. In embodiments where the compressor  104  is a single-speed compressor, this may result in excess compressor capacity during the dryer operation, e.g., when the laundry is partially dry but not completely dry. Such excess compressor capacity may result in an increased thermal load, e.g., at the condenser  108  downstream of the compressor  104 . In order to reduce the thermal load at the condenser  108  during this portion of the drying operation, the condenser  108  may be selectively in thermal communication with condensate  121 , as shown in various example embodiments illustrated in  FIGS. 5 through 10  and described further below. 
     As may be seen in  FIGS. 4 through 7 , the dryer appliance  10  may include a sump or condensation tank  120  configured to receive condensate  121  from the evaporator  102 . Condensate from the evaporator  102  may flow into the condensation tank  120  via condensate line  124 , e.g., as illustrated in  FIGS. 5 and 6 . In some embodiments, condensate  121  may be stored in a holding tank  118  upstream of the condensate tank  120  until heat exchange, as described in more detail below, is needed. A heat exchanger  115 , in particular a refrigerant to water heat exchanger such as the portion of line  114  illustrated in  FIGS. 4 through 7 , may be provided in the condensation tank  120 . As best seen in  FIGS. 5 through 7 , the condensate  121  within the condensation tank  120  may be selectively in thermal communication with the condenser  108  via the heat exchanger  115  based on a fill level of the condensate  121  within the condensation tank  120 . In some exemplary embodiments, e.g., as shown in  FIGS. 5 and 6 , the condensate in the condensation tank may be not in thermal communication with the condenser  108  via the heat exchanger  115  when the condensation tank  120  is filled to a first level  140 , and the condensate  121  may be in thermal communication with the condenser  108  via the heat exchanger  115  when the condensation tank  120  is filled to a second level  142 . In some exemplary embodiments, e.g., as illustrated in  FIG. 7 , the condensate  121  may be not in thermal communication with the condenser  108  via the heat exchanger  115  when the condensate  121  is held within holding tank  118  and the condensate  121  may be in thermal communication with the condenser  108  via the heat exchanger  115  when the condensation tank  120  is filled, e.g., by gravity flow, when valve  122  is opened. When the condensation tank  120  is filled to a level such that the heat exchanger  115  is submerged, the heat exchanger may be activated such that thermal energy from the condenser  108  may be absorbed by refrigerant within line  114  and transferred to water, e.g., condensate,  121  in the condensation tank  120  when the refrigerant flows through the heat exchanger  115 , e.g., the portion of line  114  extending through the condensation tank  120 , as illustrated for example in  FIGS. 4 through 7 . For example, the heat exchanger  115  may be positioned within the condensation tank  120  at a height along the vertical direction V such that when the condensation tank  120  is filled to the first level  140  the heat exchanger  115  is above the condensate  121  and not in direct contact with the condensate  121 , and when the condensation tank  120  is filled to the second level  142  (which is greater than the first level  140 ), the heat exchanger  115  is submerged in the condensate  121  and thereby the heat exchanger  115  is activated as described above. 
     As seen in  FIGS. 5 through 7 , a valve  122  may be provided in the condensate line  124  upstream of the condensation tank  120 , such as downstream of holding tank  118  and upstream of the condensation tank  120 , e.g., as in the embodiment of  FIG. 7 . In such embodiments, the controller  56  may be in operative communication with the valve  122 . Additionally, a temperature sensor  51  ( FIG. 2 ) such as a thermistor or any other suitable temperature sensor may be provided to sense a temperature of the heating system  40 . For example, as illustrated in  FIG. 2 , the temperature sensor  51  may be configured to sense a temperature of air  152  flowing between the chamber  25  and the evaporator  102 . In various embodiments, one or more temperature sensors may be provided, and the temperature sensor(s) may also or instead be configured to sense a temperature of refrigerant within the heating system  40  and/or a temperature of a casing within the heating system  40 , such as a compressor case. For example, the controller  56  may be configured to open the valve  122  when the sensed temperature, e.g., of air  152 , is greater than a predetermined threshold temperature. As mentioned, the sensed temperature may also or instead be a sensed temperature of the refrigerant and/or a case of the compressor  104 . In various embodiments, the controller  56  may be configured to open the valve  122  such that the condensation tank  120  is filled to the second level  142 . For example, the controller  56  may be configured to open the valve  122  for a predetermined amount of time when the sensed temperature is greater than the predetermined threshold temperature. The predetermined time may be a sufficient amount of time, given a known flow rate of condensate  121  through condensate line  124 , to fill condensation tank  120  to the second level  142 . In another example, the controller  56  may be in operative communication with a float switch  143  configured to detect when the condensate  121  within condensation tank  120  has reached the second level  142  and the controller  56  may be configured to close the valve  122  upon receiving a signal from the float switch  143  indicating that the condensation tank  120  is filled to the second level  142 . In some embodiments, e.g., as shown in  FIGS. 5 and 6 , the float switch  143  may be a second float switch and a first float switch  141  may be provided to sense when the water, e.g., condensate,  121  has filled the tank  120  to the first level  140 . The structure and function of such float switches are understood by those of skill in the art and are not described in further detail herein. 
     Turning now to  FIG. 6 , an additional exemplary embodiment is shown wherein water may be provided to the condensation tank  120  as needed, e.g., when condensation is not available in a sufficient quantity to submerge the heat exchanger  115 . In the example embodiment illustrated by  FIG. 6 , a water supply, such as a residential plumbing system, may be in fluid communication with the condensation tank  120  via a conduit  123  with a valve  125  upstream of the condensation tank  120 . 
     As illustrated for example in  FIG. 7 , in some embodiments the condensate  121  may gradually accumulate in the holding tank  118  during operation of the heating system  40 . The condensate  121  may then be stored in the holding tank  118  until needed. For example, the condensate  121  may be stored in the holding tank  118  until the sensed temperature, e.g., of the air  152 , refrigerant, and/or compressor  104 , is greater than the predetermined threshold temperature, as described above. As shown in  FIG. 7 , the holding tank  118  may be positioned above the condensate tank  120  along the vertical direction V, such that condensate  121  may flow into the condensate tank  120  from the holding tank  118  by gravity. 
     Also shown in  FIGS. 5 through 7  is a drain pump  130 . The drain pump  130  may be in fluid communication with the condensation tank  120  such that the drain pump  130  may extract condensate  121  from the condensation tank  120  and provide a flow of condensate to drain conduit  132 . The controller  56  may be in operative communication with the drain pump  130 . For example, the controller  56  may be configured to deactivate the drain pump  130  when the sensed temperature of air  152  flowing between the chamber  25  and the evaporator  102  is greater than the predetermined threshold temperature, such that condensate  121  continually flowing into the condensation tank  120  fills the condensation tank  120  to the second level. Additionally, a temperature sensor  126  may be positioned in the condensation tank  120  and configured to sense a temperature of the water, e.g., condensate, in the condensation tank  120 . For example, it may be desirable to ensure that the condensate  121  is not excessively heated, e.g., to or above a boiling point. Accordingly, in some embodiments, the controller  56  may also be in operative communication with the temperature sensor  126  to receive a signal from the temperature sensor  126  indicative of the temperature of the condensate  121  in the condensation tank  120 . The controller  56  may be further configured to activate the drain pump  130  when the sensed temperature of the condensate  121  in the condensation tank  120  is greater than a predetermined drain temperature. As such, the condensation tank  120  may be completely or substantially drained when the sensed temperature of the condensate  121  in the condensation tank  120  is greater than the predetermined drain temperature, e.g., to a fill level below the first level  140 . The condensation tank  120  may be subsequently re-filled, e.g., to an intermediate level between the first level  140  and the second level  142 , or to the second level  142  when additional or continued heat exchange is desired after draining the tank  120 . In various embodiments, the condensation tank  120  may be re-filled with water from condensate line  124  and/or a water supply such as a residential plumbing system, e.g., as in the embodiment illustrated by  FIG. 6 . For example, the condensation tank  120  may be re-filled by opening the valve  122  in a similar manner as described above. As another example, as shown in  FIG. 6 , water supply valve  121  may be provided upstream of the condensation tank  120  to selectively provide water from a residential plumbing system to the condensation tank  120 . In such embodiments, the controller  56  may be further configured to open the water supply valve  121  after activating the drain pump  130  such that the condensation tank  120  is re-filled. In some embodiments, the condensation tank  120  may be re-filled with the water supply valve  121  to an intermediate level greater than the first level  140  and less than the second level  142 . 
       FIG. 8  provides a flow chart of an exemplary method  200  of operating a dryer appliance according to one or more additional embodiments of the present disclosure. Method  200  may begin with an initial step  202  of turning the system on. During operation, as described above, the dryer appliance  10  may provide the flow of air  150  from the condenser  108  to the chamber  25  and discharge the air  152  from the chamber  25  to the evaporator  102 . Operation of the dryer appliance  10  may also include circulating air  154  from the evaporator  102  to the condenser  108 , and, as mentioned above, moisture from the air  152  may condense at the evaporator  102  before the air  154  is circulated to the condenser  108 . Further, the exemplary steps in  FIG. 8  illustrate one embodiment in which the method  200  includes transferring thermal energy from the condenser  108  to the condensate  121 . As mentioned above, a temperature sensor  51  ( FIG. 2 ) may be provided for sensing a temperature of the heating system  40 , e.g., of air  152  discharged from the chamber  25  to the evaporator  102 . Accordingly, the method  200  may include determining, at step  204 , whether the sensed temperature is greater than the predetermined threshold temperature. As mentioned, the sensed temperature may be any one or more of an air temperature, a refrigerant temperature, or a surface temperature, e.g., of a surface of the compressor  104 . In such embodiments, condensate  121  may be collected in the condensation tank  120 , e.g., via condensate line  124 , so as to fill the condensation tank  120  to the first level  140  at step  206  when the sensed temperature is less than the predetermined threshold temperature. Condensate  121  may be collected in the condensation tank  120  so as to fill the condensation tank  120  to the second level  142  at step  208  when the sensed temperature is greater than the predetermined threshold temperature. As mentioned above, the heat exchanger  115  in the condensation tank  120  is activated when the condensation tank  120  is filled to the second level  142 . Additionally, in some embodiments, the method  200  may continually monitor the temperature, e.g., of the air  152 , refrigerant within the heating system  40 , and/or the compressor  104 . Thus, for example, the method  200  may also include returning to step  204  after filling the condensation tank  120  to the first level  140  at step  206 . 
     Method  200  may further include sensing a temperature of the condensate  121  in the condensation tank  120 , e.g., with a temperature sensor such as sensor  126  in  FIGS. 5 through 7 , and determining, at step  210 , whether the sensed condensate temperature is less than a predetermined drain temperature. Method  200  may also include draining the condensation tank  120  at step  212  when the sensed temperature of the condensate  121  in the condensation tank  120  is greater than or equal to (e.g., not less than) the predetermined drain temperature. After draining the condensation tank  120  at step  212 , the method  200  may also include a step  214  of re-filling the tank  120 , e.g., to an intermediate level greater than the first level and less than the second level, as described above. For example, the intermediate fill may be provided with condensate from condensate line  124  and/or from a separate water supply. As mentioned above, the method  200  may continually monitor the temperature of the air  152 . Accordingly, in some embodiments, the method  200  may return to step  204  after step  210  and/or step  214 . 
       FIGS. 9 and 10  illustrate additional embodiments, wherein the drain pump  130  may supply water, e.g., condensate  121 , from the tank  120  to a spray head  134  via conduit  132 . The drain pump  130  may supply the condensate  121  from the condensate tank  120  or from condensate line  124 . In various embodiments, the spray head  134  may be configured to spray the condensate  121  on the condenser  108  such that the condensate  121  may directly absorb thermal energy from the condenser  108 . Accordingly, additional embodiments of the present disclosure may include methods of operating the dryer appliance  10  wherein thermal energy is transferred from the condenser  108  to the condensate  121  by spraying the condensate  121  on the condenser  108 . As may be seen in  FIGS. 9 and 10 , the condenser  108  may include a plurality of fins  109  (only selected fins  109  are specifically numbered for sake of clarity) extending between a pair of end panels  107 . One of ordinary skill in the art will understand that air  154  flows between and around the fins  109 , and the fins  109  are configured to provide an optimal surface area for heat exchange between the air  154  and refrigerant within the condenser  108 . Accordingly, as shown in  FIG. 9 , in some embodiments the spray head  134  may be configured to spray the condensate  121  on one or the end panels  107  of the condenser  108 , such that the condensate does not enter the air  154 . Additional exemplary embodiments of the present disclosure include methods of operating the dryer appliance  10  which comprise spraying the condensate  121  on one of the end panels  107 . In other embodiments, as shown in  FIG. 10 , the spray head  134  may be configured to spray the condensate  121  on the plurality of fins  109  of the condenser  108 . Thus, additional exemplary embodiments of the present disclosure include methods of operating the dryer appliance  10  which comprise spraying the condensate  121  on the plurality of fins  109  of the condenser  108 . Spraying the condensate  121  on one of the end panels  107  may advantageously prevent introducing additional humidity into the chamber  25 , e.g., via air  150 . Spraying the condensate  121  on the plurality of fins  109  may advantageously provide increased contact between the condensate  121  and the condenser  108  to more rapidly transfer thermal energy from the condenser  108  to the condensate  121 . 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.