HEAT PUMP DRYER INCLUDING A BOOST HEATER

Abstract

A laundry appliance includes a cabinet including an appliance base and a basement. The basement includes a basement inlet and a basement outlet. A drum is rotatably supported in the cabinet. A drum motor is operatively connected to rotate the drum. A heat exchanger is arranged in the basement between the basement inlet and the basement outlet. A refrigerant system is connected to the heat exchanger. The refrigerant system includes a compressor configured to circulate an amount of flammable refrigerant through the heat exchanger. A boost heater is arranged at the basement outlet between the heat exchanger and the drum.

Description

FIELD

The present disclosure relates to the art of laundry appliances and, more particularly, to a heat pump dryer having a boost heater.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Laundry appliances are prolific in both residential and commercial settings. The laundry appliance may be a dryer machine that is used to dry laundry after it has been cleaned in a washing machine. In some examples, the laundry appliance may be a washer and dryer combination appliance where a single machine performs both the washing and drying functions. There are a number of different names used to describe washer and dryer combination appliances, including without limitation, “washer/dryer combos” and “all-in-one washer dryers.”

Many laundry appliances include a cabinet (i.e., an appliance housing) with an opening that is accessed by an appliance door. A drum is positioned in the cabinet and is rotatable with respect to the cabinet. The drum typically has a drum opening that provides access to a laundry compartment inside the drum. The appliances also include a blower that directs airflow into the drum. In a heat exchanger dryer, airflow is passed through one or more heat exchangers prior to entering the drum, such as and including an evaporator with evaporator coils and a condenser with condenser coils. The evaporator and condenser coils remove moisture and heat from the airflow.

The evaporator and condenser coils are typically connected to a refrigerant system including a compressor. The compressor is connected in fluid communication with the evaporator and the condenser. The compressor directs pressurized refrigerant through the evaporator and the condenser which, in turn heats air flowing over the evaporator and condenser coils. The amount of work required by the compressor varies and may depend upon ambient temperature. The lower the ambient temperature, the more work required from the compressor to heat the airflow. While in operation, the compressor generates heat. Heat in the compressor may detract from an overall operational efficiency of the refrigerant system. As such, many heat pump dryers include an auxiliary fan that directs an airflow over the compressor to reduce compressor temperatures.

Heat exchanger dryers sometimes include a boost heater that is operated during an initial portion of a drying cycle. The boost heater quickly raises the operating temperature of air passing through the evaporator and condenser. Operation of the boost heater reduces the amount of work needed by the compressor and heat exchanger(s) to generate an airflow having the desired operating temperatures. By reducing the amount of work needed to be input by the compressor and heat exchanger(s) results in a reduction of cycle time and operating costs.

SUMMARY

This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

A laundry appliance, in accordance with the present disclosure, includes a cabinet including an appliance base and a basement supported on the appliance base. The basement includes a basement inlet and a basement outlet. A drum is rotatably supported in the cabinet. A drum motor is operatively connected to rotate the drum. A heat exchanger is arranged in the basement between the basement inlet and the basement outlet. The basement outlet is connected in fluid communication with the drum. The heat exchanger includes an evaporator having an evaporator coil and a condenser having a condenser coil. A refrigerant system is connected in fluid communication with the heat exchanger. The refrigerant system includes a compressor having a refrigerant inlet and a refrigerant outlet arranged in the basement. The compressor is configured to circulate an amount of flammable refrigerant through the evaporator coil and the condenser coil. A blower assembly includes a blower motor operable to generate an airflow through the basement. The airflow passes in a heat exchange relationship with the evaporator and the condenser. A boost heater is arranged at the basement outlet between the heat exchanger and the drum. The boost heater is in a flow path of the airflow.

A method of operating a laundry appliance having a heat pump and a flammable refrigerant system in accordance with the present disclosure, includes receiving a start signal, and selectively activating, through a controller, one or more of a drum motor, a blower motor, a compressor, and a boost heater to maintain inrush current below a selected current threshold.

The present disclosure describes systems for pre-heating air in a heat pump dryer that employs a flammable refrigerant such as a hydrocarbon based refrigerant or a hydrofluoroolefin based refrigerant. The systems not only ensure that the boost heater does not reach temperatures that approach a flash point of the flammable refrigerant through the use of PTC, tubular, and liquid heating devices, but also controls those devices to pre-heat the airflow without causing high electrical currents that might trip a circuit breaker and become a nuisance to a consumer.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure.

FIG. 1 is a front perspective view of a laundry appliance including a compressor cooling system, in accordance with the present disclosure;

FIG. 2 is a rear perspective view of the exemplary laundry appliance shown in FIG. 1, in accordance with the present disclosure;

FIG. 3 is a partial cross-sectional side view of the exemplary laundry appliance shown in FIG. 1, in accordance with the present disclosure;

FIG. 4 is a perspective view of the basement arranged in the laundry appliance of FIG. 1 including a boost heater, in accordance with the present disclosure;

FIG. 5 is a top view of the basement of FIG. 4, in accordance with an aspect of the disclosure;

FIG. 6 is a plan view of a boost heater including positive temperature coefficient heating elements, in accordance with an aspect of the present disclosure;

FIG. 7 is a plan view of a boost heater including tubular heating elements, in accordance with an aspect of the present disclosure;

FIG. 8 is a plan view of a boost heater including a liquid medium heat exchange system, in accordance with an aspect of the present disclosure; and

FIG. 9 is a controller for selectively controlling electrical loads in the laundry appliance including the boost heater, in accordance with the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Exemplary will now be described more fully with reference to the accompanying drawings.

Due to various environmental concerns, there is a current trend to move away from the use of hydrofluorocarbons, such as R134a, in refrigerant systems. Manufacturers are exploring alternative products including various flammable refrigerants including hydrocarbon based refrigerants such as R290, hydrofluoroolefin based refrigerants, and the like.

With reference to FIGS. 1-3, a laundry appliance 50 is illustrated. The laundry appliance 50 is a dryer machine and more specifically, a heat pump dryer machine. The laundry appliance 50 is illustrated as having a front-load configuration, although it may alternatively have a top-load configuration.

The laundry appliance 50 includes a cabinet 52 that is rectangular in shape. The cabinet 52 includes a front cabinet wall 54 having a front cabinet opening 56, a rear cabinet wall 58 opposite the front cabinet wall 54, a set of cabinet sidewalls 60 that extend between the front cabinet wall 54 and the rear cabinet wall 58, a top cabinet wall 62, and a bottom cabinet wall 64. The front cabinet wall 54, rear cabinet wall 58, set of cabinet sidewalls 60, top cabinet wall 62, and bottom cabinet wall 64 cooperate to define a cabinet cavity 68 (FIG. 3) inside the cabinet 52. In accordance with a non-limiting example, front cabinet wall 54 includes a vent 69 (FIG. 1) that facilitates air flow into cabinet cavity 68 as will be detailed more fully herein.

In some configurations, the laundry appliance 50 may include a control panel 70 that is attached to the front cabinet wall 54. The control panel 70 may be positioned adjacent to the top cabinet wall 62. The control panel 70 may include a display 72, a speaker 74, a control selector 76, and a control module 78. The display 72 may be used to display information, adjust features or settings of the laundry appliance 50, present prompts to users of the laundry appliance 50, and to perform one or more other functions. The display 72 may be a touch screen display. The speaker 74 may be used to output audible sounds and to perform one or more other functions. The control selector 76 may be used to adjust features or settings of the laundry appliance 50 and to perform one or more other functions. The control module 78 may receive input from the user (e.g., via the display 72 or the control selector 76). The control module 78 may be configured to operate a cycle (e.g., a drying cycle) of the laundry appliance 50 according to the user’s input and may perform one or more other functions. Additional functions of the control module 78 will be described below. It should be appreciated that display 72, speaker 74, control selector 76, and control module 78 may be positioned in another suitable location on the laundry appliance 50.

A front appliance door 84 is pivotally connected to the cabinet 52, and more specifically, to the front cabinet wall 54 of the cabinet 52. The front appliance door 84 swings between an open door position and a closed door position. In the open door position, the front appliance door 84 provides access to the front cabinet opening 56. In the closed door position, the front appliance door 84 shuts or closes the front cabinet opening 56. When in the closed door position, the front appliance door 84 may be flush with or positioned adjacent to a front facia 86 of the cabinet 52. Although other materials can be used, in the illustrated example, the front appliance door 84 is composed of metal.

The laundry appliance 50 includes a drum 90 that is positioned in the cabinet cavity 68 and is rotatable with respect to the cabinet 52 about a drum axis 92. The drum 90 has a cylindrical shape and extends between a front drum end 94 and a rear drum end 96. The drum 90 includes a front drum opening 98 at the front drum end 94, a rear drum wall 100 at the rear drum end 96, and a drum sidewall 102 that extends between the front drum end 94 and rear drum end 96. One or more drum inlets 104 extend through the rear drum wall 100. While depicted as a dedicated dryer, it should be understood that laundry appliance 50 could also take the form of a combination washer/dryer.

The front drum end 94, the drum sidewall 102, and the rear drum wall 100 cooperate to define a laundry compartment 110 inside the drum 90. The front cabinet opening 56 in the front cabinet wall 54 and the front drum opening 98 at the front drum end 94 are at least partially aligned with one another and therefore provide access to the laundry compartment 110 inside the drum 90 when the front appliance door 84 is in the open door position. In the illustrated example, the front cabinet opening 56 in the front cabinet wall 54 and the front drum opening 98 at the front drum end 94 are aligned with the drum axis 92. It should be appreciated that in use, laundry (e.g., clothes, towels, and/or bedding, etc.) is placed inside the laundry compartment 110 where it is dried during the drying cycle of the laundry appliance 50.

Referring to FIG. 4 and with continued reference to FIGS. 1-3, the laundry appliance 50 includes an appliance base 116 disposed between the drum 90 and the bottom cabinet wall 64. The appliance base 116 is attached to the bottom cabinet wall 64. The appliance base 116 extends between a front base end 118 and a rear base end 120 that is opposite the front base end 118. The front base end 118 is positioned adjacent to and attached to the front cabinet wall 54. The rear base end 120 is positioned adjacent to and attached to the rear cabinet wall 58. The appliance base 116 extends laterally between a first base end 122 and a second base end 123 opposite the first base end 122. The first base end 122 is positioned adjacent to one of the cabinet sidewalls 60 and the second base end 123 is positioned adjacent to another one of the cabinet sidewalls 60.

The laundry appliance 50 includes a heat exchanger system 144 disposed within a basement 146 of the appliance base 116. The heat exchanger is configured to heat air flowing through the appliance base 116 towards laundry compartment 110. The basement 146 is positioned adjacent to the first base end 122 and between the front base end 118 and rear base end 120 of the appliance base 116. The basement 146 includes a front basement wall 148, a rear basement wall 150, basement sidewalls 152 extending between the front basement wall 148 and rear basement wall 150, and a bottom basement wall 154.

The front basement wall 148 is positioned adjacent to the front base end 118 of the appliance base 116. The rear basement wall 150 is positioned adjacent to the rear base end 120 of the appliance base 116. The basement 146 is arranged in fluid communication with laundry compartment 110 via a first basement opening 156 in the rear basement wall 150. The basement 146 includes a second basement opening 158 (FIG. 5) in the front basement wall 148. The bottom basement wall 154 is inclined such that the bottom basement wall 154 in a position adjacent to the rear basement wall 150, is positioned lower (e.g., closer to the bottom cabinet wall 64) than the bottom basement wall 154 in a position adjacent to the front basement wall 148. In other words, the bottom basement wall 154 in a position adjacent to the front basement wall 148, is positioned higher (e.g., closer to the top cabinet wall 62) than the bottom basement wall 154 in a position adjacent to the rear basement wall 150.

Referring to FIG. 5, the heat exchanger system 144 includes a first heat exchanger 172 and a second heat exchanger 174. In accordance with the present disclosure, first heat exchanger 172 is an evaporator (not separately labeled) and second heat exchanger 174 is a condenser (also not separately labeled). In accordance with one exemplary aspect, the first heat exchanger 172 and second heat exchanger 174 are positioned adjacent to each other. More specifically, the first heat exchanger 172 is positioned adjacent to the front cabinet wall 54, and more specifically, the front basement wall 148. The second heat exchanger 174 is positioned adjacent to the rear cabinet wall 58, and more specifically, the rear basement wall 150. In some examples, the first heat exchanger 172 and second heat exchanger 174 may abut each other.

The first heat exchanger 172 is configured to condense air flowing through vent 69 from ambient. The air is condensed before the air reaches the second heat exchanger 174. The first heat exchanger 172 includes a first pipe 176 extending through the first heat exchanger 172. The first pipe 176 is configured to carry refrigerant or another suitable fluid to aid in condensing the air. Fluid (e.g., water vapor) may be released from the first heat exchanger 172 when the first heat exchanger 172 condenses air passing through the first heat exchanger 172. More specifically, when air is condensed using the first heat exchanger, moisture is removed from the air and fluid gravitationally falls from the first heat exchanger 172 to the bottom basement wall 154 of the basement 146. The condensate is collected and delivered to a condensate holding tank 177 where it may evaporate, be withdrawn, or be used in other systems as will become more fully evident herein.

The second heat exchanger 174 is configured to heat the air flowing from the first heat exchanger 172 and out the basement 146 of the appliance base 116. The second heat exchanger 174 includes a second pipe 178 extending through the second heat exchanger 174. The second pipe 178 is configured to carry refrigerant or another suitable fluid. Accordingly, air flows through the heat exchanger system 144 to first be condensed by the first heat exchanger 172 and subsequently heated by the second heat exchanger 174 to create heated air that is passed into drum 90 via first basement opening 156.

The first pipe 176 and second pipe 178 of the first heat exchanger 172 and second heat exchanger 174 of the heat exchanger system 144 are configured to receive refrigerant or another suitable fluid from a compressor 180. The compressor 180 is attached to a compressor base 182 and to the appliance base 116. The compressor base 182 is positioned adjacent to the rear base end 120 and the second base end 123. Compressor 180 includes a refrigerant outlet 186 connected in fluid communication with second pipe 178 and a refrigerant inlet 188 connected in fluid communication with first pipe 176.

Compressor 180 pressurizes the refrigerant flowing through heat exchanger system 144. In accordance with the present disclosure, the refrigerant is a flammable based such as a hydrocarbon refrigerant or hydrofluoroolefin based refrigerant. For example, heat exchanger system 144, in accordance with the present disclosure, employed R290 as a refrigerant. When compressed, the temperature of the refrigerant increases. The increase in temperature is passed into the airflow passing through heat exchanger system 144. A temperature probe 190 is mounted at refrigerant inlet 188. Temperature probe 190 is operatively connected to control module 78. Control module 78 monitors the temperature of the refrigerant passing into heat exchanger system 144.

The appliance base 116 includes an airflow channel 210 disposed adjacent to the basement 146. The airflow channel 210 extends between a first channel end 212 and a second channel end 214 that is opposite the first channel end 212. A sidewall 216 extends between and connects the first channel end 212 with the second channel end 214 through a bend portion 217. The first channel end 212 is arranged in fluid communication with the basement 146 via the second basement opening 158. The second channel end 214 is positioned at the front base end 118 the appliance base 116 and adjacent to the second base end 123 of the appliance base 116. More specifically, second channel end 214 is arranged adjacent to vent 69 and receives ambient air that is directed into basement 146. As shown in FIG. 2, basement 146 is connected in fluid communication with drum 90 via a connector channel 218. More specifically, first basement opening 156 is connected in fluid communication with connector channel 218 which, in turn, is connected in fluid communication with drum 90 as will be detailed herein.

The connector channel 218 extends between a first connector end 220 and a second connector end 222 that is opposite the first connector end 220. The first connector end 220 is arranged in fluid communication with first basement opening 156. The second connector end 222 is arranged in fluid communication with the laundry compartment 110 of the drum 90 via one or more drum inlets 104 (shown in FIG. 3).

In a non-limiting example, a filter 224 is positioned across second basement opening 158 and includes an effective filter area of at least about 400 millimeters (mm) by about 175 millimeters (mm). This effective filter area of filter 224 ensures that a robust flow of air will pass through heat exchanger system 144. The robust flow of air reduces operational stress on compressor 180 that may lead to elevated refrigerant temperatures. Filter 224 captures and prevents particulate that may be entrained in air passing through airflow channel 210 from entering heat exchanger system 144. Laundry appliance 50 may include an additional filter (not shown) in the form of a lint trap arranged in airflow channel 210 upstream from filter 224. The lint trap may be accessible through front facia 86.

A blower 230 (FIG. 4) is configured to blow air through the airflow channel 210, through basement 146 across first heat exchanger 172 and second heat exchanger 174, and into drum 90. The blower 230 includes a squirrel cage or blower fan 232 arranged at second channel end 214 of airflow channel 210. Blower fan 232 is operatively connected to a motor 234 that is positioned in the appliance base 116. The motor 234 is positioned adjacent to the front base end 118 and the second base end 123 of the appliance base 116.

The motor 234 is positioned between the airflow channel 210 and the compressor base 182. In accordance with an exemplary aspect, motor 234 may be a variable speed motor that is operatively connected to control module 78. In accordance with another exemplary aspect, motor 234 may take the form of a variable speed dual rotor motor having a drum motor portion 236 operatively connected to drum 90 and a blower motor portion 238 operatively connected to blower fan 232. Of course, it should be understood that laundry appliance 50 may include separate motors operatively associated with drum 90 and blower fan 232. Blower fan 232 may be connected in fluid communication with vent 69 in front facia 86 in the case of an open loop system or may be connected to a duct 240 (FIG. 3) arranged along front cabinet wall 54. Duct 240 includes a duct opening 242 that is connected in fluid communication with front drum opening 98 in the case of a closed loop system. A lint trap, not shown, may be arranged at duct opening 242.

A base cover 244 is sealingly engaged with (i.e., seals against) the appliance base 116 and is disposed on top of the appliance base 116. More specifically, the base cover 244 extends over and encloses the basement 146 and the airflow channel 210. The base cover 244 and the basement 146 cooperate to define a basement cavity 246. Blower 230 includes an outlet 248 that directs air through airflow channel 210 into basement cavity 246. The air passes in heat exchange relationship with first heat exchanger 172 and second heat exchanger 174. First heat exchanger 172 removes moisture from the air and second heat exchanger 174 increases a temperature of the air. The air is then directed back into laundry compartment 110.

In accordance with the present disclosure, laundry appliance 50 includes a boost heater 310 that operates to preheat the air flowing through basement cavity 246 until heat exchanger system 144 comes to operating temperature. In accordance with an exemplary aspect, boost heater 310 is arranged downstream of heat exchanger system 144. More specifically, boost heater 310 is positioned between second heat exchanger 174 and first basement opening 156 as shown in FIG. 3. Given that heat exchanger system 144 operates with a flammable refrigerant such as a hydrocarbon based refrigerant or a hydrofluoroolefin based refrigerant, surface temperatures in boost heater 310 are controlled. More specifically, boost heater 310 is designed to have surface temperatures below a flash point of the flammable refrigerant.

Reference will now follow to FIG. 6 in describing a boost heater 310 in accordance with a non-limiting example. Boost heater 310 includes a housing 318 having an inlet portion 320, an outlet portion 322, and an airflow path 24 that is connected in fluid communication with heat exchanger system 144. More specially, airflow path 324 is arranged at an outlet of second heat exchanger 174.

In a non-limiting example, boost heater 310 includes a plurality of heating elements 330 arranged in housing 318. More specifically, plurality of heating elements 330 arranged in a plurality of heating circuits 332. Heating elements 330, in the example depicted in FIG. 6, take the form of positive temperature coefficient (PTC) heating devices 334 arranged along airflow path 324. Each of the plurality of heating circuits includes at least one PTC heating device 334. As will be detailed more fully herein, the plurality of heating circuits 332 are connected to control module 78.

FIG. 7 depicts boost heater 310 having a plurality of heating elements 330 in the form of electrical resistive heating elements 340. Electrical resistive heating elements 340 may take the form of tubular heating elements 340, such as Calrods® or low wattage ceramic heating elements supporting a resistive wire. The electrical resistive heating elements 340 may have an electrical rating of about 1 Watt per square centimeter (W/cm²). Regardless of the form, the electrical resistive heating elements 340 are arranged along airflow path 324 and, as will be detailed more fully herein, are selectively activated to pre-heat or condition air passing from heat exchanger system 144 before first heat exchanger 172 and second heat exchanger 174 reach operating temperatures.

FIG. 8 depicts boost heater 310 with a liquid heat exchanger system 345. Unlike PTC and tubular heating elements where the source of heat lies directly in the flow path coming from heat exchanger system 144, liquid heat exchanger system 345 includes a heating coil 348 that circulates a heated liquid in a heat exchange relationship with air moving along airflow path 324. A source of heated liquid 360 is remote from heat exchanger system 144. More specifically, source of heated liquid 360 is isolated from fluid passing from heat exchanger system 144 along airflow path 324.

Source of liquid 380, in accordance with the present disclosure, includes an amount of water held in a tank 363 within which is arranged a heating element 365. Tank 363 is connected in fluid communication with heating coil 348 through a return conduit 368 and a delivery conduit 370. A pump 372 is connected in fluid communication with delivery conduit 370. Pump 372 circulates heated liquid through heating coil 348 to raise the temperature of air leaving heat exchanger system 144 before first heat exchanger 172 and second heat exchanger 174 reach operating temperatures. At this point, it should be understood that while the heating element 365 is shown in tank 363, other locations are also contemplated including along delivery conduit 370.

Reference will now follow to FIG. 9 in describing control module 78 in accordance with a non-limiting example. Control module 78 is connected to a sensor 376 that may be arranged in duct 240 to sense one or more parameters of air passing from drum 90. Sensor 376 may detect air temperature, relative humidity, or the like. Control module 78 includes a central processing unit (CPU) 382 operatively and functionally connected to a non-volatile memory module 384. Control module 78 also includes a dryer control module 386 that may control drum speed, blower speed, and compressor 180 and a boost heat control module 388 that controls heating elements 330.

Control module 78 controls compressor 180, motor 234, and boost heater 310 to avoid high in-rush currents that many activate a circuit breaker connected to a circuit powering laundry appliance 50. For example, PTC heating devices 334 have a power draw that is proportional to airflow. That is, the greater the airflow, the higher the current used by the PTC heating devices 334. During a startup phase of laundry appliance 50, motor 234 drives blower 230 at high speeds. As such, during the same period, PTC heating devices 334 have a high current draw. As will be detailed herein, control module 78 controls each of compressor 180, motor 234, and boost heater 310 to avoid high initial currents.

Upon receiving a start signal through, for example, display 72, control module 78 may stagger the activation of each of the compressor 180, motor 234, and boost heater 310. That is, dryer control module 386 and boost heater control module 388 may orchestrate a delay between the activation of compressor 180, motor 234, and boost heater 310 so as to avoid a high initial current draw. In one aspect, boost heater 310 is activated at a selected time period after the activation of compressor 180. In another exemplary aspect, boost heater 310 may be activated before compressor 180.

In another non-limiting example, control module 78 may selectively activate the PTC heating devices 334. In other words, control module 78 may initially activate one of the plurality of heating circuits 332 at start up, and then after a time delay, add in a second one of the plurality of heating circuits 332, and, if so equipped, after a second time delay a third one of the plurality of heating circuits 332. By staggering activation of the plurality of heating circuits, high in-rush currents can be avoided. The same activation may be used for the electrical resistive heating elements such as tubular heating 340.

In yet another non-limiting example, control module 78 may initially activate motor 234 at a low speed so that air current passing over, for example, PTC heating devices 334 are initially low. Once compressor 180 is activated, control module 78 may gradually increase the speed of motor 234 to heat the air passing through heat exchanger system 144 before first heat exchanger 172 and second heat exchanger 174 reach operating temperatures.

Regardless of how boost heater 310 is brought into activation, operation continues until sensor 376 detects a change in a parameter of the air passing through drum 90. For example, boost heater 310 may be turned off after the air passing from drum 90 reaches a specific temperature. Boost heater 310 may then be activated based on sensed relative humidity to provide a finishing heat to articles on laundry compartment 110.

For example, laundry appliance 50 may continue to operate with blower 230 and compressor 180 until articles in drum 90 achieve a selected remaining moisture content (RMC). The selected RMC may vary for each cycle and may range between about 25% and about 10%. Once the RMC is below the selected RMC, boost heater 310 may be reactivated until the end of the cycle to provide a finishing heat to the articles of clothing. The end of the cycle may be signaled when the RMC falls below about 2%. At this point the articles of clothing may be withdrawn from drum 90 having a warmth that is pleasing to the consumer.

At this point, it should be clear that the present disclosure describes systems for pre-heating air in a heat pump dryer that employs a flammable refrigerant such as a hydrocarbon based refrigerant or a hydrofluoroolefin based refrigerant. The systems not only ensure that the boost heater does not reach temperatures that approach a flash point of the flammable through the use of PTC, tubular, and liquid heating devices, but also controls those devices to pre-heat the airflow without causing high electrical currents that might trip a circuit breaker and become a nuisance to a consumer. At this point, it should be understood that additional heating devices, including low wattage electric resistive heating elements may also be used.

Exemplary embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that exemplary may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some exemplary, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular exemplary only and is not intended to be limiting. As used herein, the singular forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being "on," “engaged to,” "connected to," or "coupled to" another element or layer, it may be directly on, engaged, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," “directly engaged to,” "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer, or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the exemplary.

Spatially relative terms, such as “inner,” “outer,” "beneath," "below," "lower," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. A laundry appliance comprising:

a cabinet including an appliance base;

a basement supported on the appliance base, the basement including a basement inlet and a basement outlet;

a drum rotatably supported in the cabinet;

a drum motor operatively connected to rotate the drum;

a heat exchanger arranged in the basement between the basement inlet and the basement outlet, the basement outlet connected in fluid communication with the drum, the heat exchanger including an evaporator having an evaporator coil and a condenser having a condenser coil;

a refrigerant system connected in fluid communication with the heat exchanger, the refrigerant system including a compressor having a refrigerant inlet and a refrigerant outlet arranged in the basement, the compressor being configured to circulate an amount of flammable refrigerant through the evaporator coil and the condenser coil;

a blower assembly including a blower motor operable to generate an airflow through the basement, the airflow passing in a heat exchange relationship with the evaporator and the condenser; and

a boost heater arranged at the basement outlet between the heat exchanger and the drum, the boost heater being in a flow path of the airflow.

2. The laundry appliance according to claim 1, wherein the boost heater includes a positive temperature coefficient (PTC) heating device.

3. The laundry appliance according to claim 1, wherein the boost heater includes an electric resistive heating element.

4. The laundry appliance according to claim 3, wherein the electric resistive heating element comprises a tubular heating element.

5. The laundry appliance according to claim 3, wherein the electric resistive heating element includes an electrical rating of about 1 W/cm2.

6. The laundry appliance according to claim 1, wherein the boost heater includes a heat exchanger, an amount of fluid, and a pump, the pump being operable to circulate the amount of fluid through the heat exchanger.

7. The laundry appliance according to claim 1, further comprising a controller operatively connected to the drum motor, the blower motor, the compressor, and the boost heater, the controller selectively activating one or more of the drum motor, the blower motor, the compressor, and the boost heater to maintain inrush current below a selected current threshold.

8. The laundry appliance according to claim 7, wherein the controller activates each of the drum motor, the blower motor, the compressor, and the boost heater in a selected order to maintain the inrush current below the selected current threshold.

9. The laundry appliance according to claim 7, wherein the drum motor and the blower motor form a variable speed dual rotor motor including a drum motor portion and a blower motor portion, the controller selectively increasing motor speed of at least one of the blower motor portion and the drum motor portion to maintain the inrush current below the selected current threshold.

10. The laundry appliance according to claim 7, wherein the boost heater includes a plurality of heater circuits, the controller selectively activating select ones of the plurality of heater circuits to maintain the inrush current below the selected current threshold.

11. The laundry appliance according to claim 7, further comprising a sensor exposed to the airflow through the drum, the controller selectively activating each of the drum motor, the blower motor, the compressor, and the boost heater to maintain the inrush current below the selected current threshold based on an airflow parameter detected by the sensor.

12. The laundry appliance according to claim 11, wherein the airflow parameter includes at least one of temperature of the airflow, and relative humidity of the airflow.

13. A method of operating a laundry appliance having a heat pump and a flammable refrigerant system, the method comprising:

receiving a start signal; and

selectively activating, through a controller, one or more of a drum motor, a blower motor, a compressor, and a boost heater to maintain inrush current below a selected current threshold.

14. The method of claim 13, wherein the controller selectively activates the boost heater by providing electrical current to a positive temperature coefficient (PTC) heating device.

15. The method of claim 14, wherein the controller selectively activates the blower motor and activates the PTC heating device.

16. The method of claim 15, wherein the controller gradually increases a rotational speed of the blower motor when activating the PTC heating device.

17. The method of claim 14, wherein the controller selectively activates the boost heater by providing electrical current to an electric resistive heating element.

18. The method of claim 17, wherein the step of providing electrical current to an electric resistive heating element includes providing electrical current to an electrical resistive heater having an electrical rating of about 1 W/cm2.

19. The method of claim 13, wherein the controller initiates a time delay between activations of the compressor, the boost heater, and the blower motor.

20. The method of claim 19, wherein the boost heater is activated after activating the compressor.

21. The method of claim 13, wherein the boost heater includes a plurality of heater circuits, each of the plurality of heating circuits, the controller selectively activating the boost heater by providing power to one of the plurality of heating circuits before activating others of the plurality of heating circuits.

22. The method or claim 21, wherein the each of the plurality of heating circuits includes a positive temperature coefficient (PTC) heating device.

23. The method of claim 21, wherein each of the plurality of heating circuits includes an electrical resistive heating element.

24. The method of claim 21, wherein the controller activates the others of the plurality of heating circuits based on a cycle parameter.

25. The method of claim 24, wherein the cycle parameter includes at least one of a time parameter, a temperature parameter, a humidity parameter, and an electrical parameter.

26. The method of claim 13, wherein the controller selectively activates the boost heater based on a remaining moisture content (RMC) of articles in the laundry appliance.

27. The method of claim 26, wherein the boost heater is selectively activated when the RMC is less than about 25%.

28. The method of claim 26, wherein the boost heater is selectively activated when the RMC is less than about 20%.

29. The method of claim 26, wherein the boost heater is selectively activated when the RMC is less than about 10%.

30. The method of claim 13, wherein the controller selectively deactivates the boost heater when the remaining moisture content (RMC) of articles in the laundry appliance is about 2%.