Refrigerator appliance and arc-resistant heating assembly

A refrigerator appliance and an arc-resistant heating assembly are provided herein. The refrigerator appliance may include a cabinet defining a chilled chamber, a sealed system, and an electrical heater. The electrical heater may include a resistive element, a sheath, a thermally conductive electrical insulation, and an internal insulator. The sheath may be disposed about the resistive element from a first end portion to a second end portion. The thermally conductive electrical insulation may be radially positioned between the resistive element and the sheath. The internal insulator may be radially positioned between the resistive element and the thermally conductive electrical insulation.

FIELD OF THE INVENTION

The present subject matter relates generally to electrical heating assemblies, and more particularly to heating assemblies for refrigerator appliances.

BACKGROUND OF THE INVENTION

Refrigerators or refrigerator appliances generally include a cabinet that defines a chilled chamber. The chilled chamber is commonly cooled with a sealed system having an evaporator. One problem that may be encountered with existing refrigerator appliances is inefficient defrosting of the evaporator. For example, when the evaporator is active, frost can accumulate on the evaporator and thereby reduce efficiency of the evaporator. One effort to reduce or eliminate frost from the evaporator has been to utilize a heater, such as an electrical heater, to heat the evaporator when the evaporator is not operating.

Utilizing an electrical heater to defrost an evaporator can pose certain challenges. For example, certain refrigerators utilize a flammable refrigerant within the sealed system. In such systems, a surface temperature of the heater is generally limited to a temperature well below the auto-ignition temperature of the flammable refrigerant. However, the evaporator generally requires a certain power output from the heater to suitably defrost. Moreover, it is possible that a portion of electrical heater may fail (e.g., following unforeseen damage to the electrical heater). In some instances, a portion of the electrical heater may short-circuit and spark. For example, a heating element may rupture or zipper, resulting in a potential electrical arc from the heating element.

Accordingly, a heating assembly with certain safety features would be useful. In particular, a heating assembly that is configured to prevent zippering in a refrigerator appliance. Moreover, it may also be useful to have a refrigerator appliance with a heating assembly for defrosting an evaporator of the refrigerator appliance while also operating well below an auto-ignition temperature of a flammable refrigerant within the evaporator would be useful.

BRIEF DESCRIPTION OF THE INVENTION

In one exemplary aspect of the present disclosure, a refrigerator appliance is provided. The refrigerator appliance may include a cabinet defining a chilled chamber, a sealed system, and an electrical heater. The sealed system may include an evaporator. The evaporator may be disposed at the chilled chamber. The electrical heater may be positioned adjacent the evaporator. The electrical heater may include a resistive element, a sheath, a thermally conductive electrical insulation, and an internal insulator. The sheath may be disposed about the resistive element from a first end portion to a second end portion. The thermally conductive electrical insulation may be radially positioned between the resistive element and the sheath. The internal insulator may be radially positioned between the resistive element and the thermally conductive electrical insulation.

In another exemplary aspect of the present disclosure, and electrical heating assembly for a consumer appliance is provided. The electrical heating assembly may include a sheath, a resistive element, a thermally conductive electrical insulation, and an internal insulator. The sheath may define an enclosed volume along a length between a first end portion and a second end portion. The resistive element may be disposed within the enclosed volume to generate heat in response to an electrical current. The thermally conductive electrical insulation may be radially positioned between the resistive element and the sheath. The internal insulator may be radially positioned between the resistive element and the thermally conductive electrical insulation.

DETAILED DESCRIPTION

The terms “includes” and “including” are intended to be inclusive in a manner similar to the term “comprising.” Similarly, the term “or” is generally intended to be inclusive (i.e., “A or B” is intended to mean “A or B or both”). The phrase “in one embodiment,” does not necessarily refer to the same embodiment, although it may.

FIG. 1provides a front view of a representative refrigerator appliance10according to exemplary embodiments of the present disclosure. More specifically, for illustrative purposes, the present disclosure is described with a refrigerator appliance10having a construction as shown and described further below. As used herein, a refrigerator appliance includes appliances such as a refrigerator/freezer combination, side-by-side, bottom mount, compact, and any other style or model of refrigerator appliance. Accordingly, other configurations including multiple and different styled compartments could be used with refrigerator appliance10, it being understood that the configuration shown inFIG. 1is by way of example only.

Refrigerator appliance10includes a fresh food storage compartment12and a freezer storage compartment14. Freezer compartment14and fresh food compartment12are arranged side-by-side within an outer case16and defined by inner liners18and20therein. A space between case16and liners18,20and between liners18,20may be filled with foamed-in-place insulation. Outer case16normally is formed by folding a sheet of a suitable material, such as pre-painted steel, into an inverted U-shape to form the top and side walls of case16. A bottom wall of case16normally is formed separately and attached to the case side walls and to a bottom frame that provides support for refrigerator appliance10. Inner liners18and20are molded from a suitable plastic material to form freezer compartment14and fresh food compartment12, respectively. Alternatively, liners18,20may be formed by bending and welding a sheet of a suitable metal, such as steel.

A breaker strip22extends between a case front flange and outer front edges of liners18,20. Breaker strip22is formed from a suitable resilient material, such as an extruded acrylo-butadiene-styrene based material (commonly referred to as ABS). The insulation in the space between liners18,20is covered by another strip of suitable resilient material, which also commonly is referred to as a mullion24. In one embodiment, mullion24is formed of an extruded ABS material. Breaker strip22and mullion24form a front face, and extend completely around inner peripheral edges of case16and vertically between liners18,20. Mullion24, insulation between compartments, and a spaced wall of liners separating compartments, sometimes are collectively referred to herein as a center mullion wall26. In addition, refrigerator appliance10includes shelves28and slide-out storage drawers30, sometimes referred to as storage pans, which normally are provided in fresh food compartment12to support items being stored therein.

Refrigerator appliance10can be operated by one or more controllers11or other processing devices according to programming or user preference via manipulation of a control interface32mounted, e.g., in an upper region of fresh food storage compartment12and connected with controller11. Controller11may include one or more memory devices and one or more microprocessors, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with the operation of the refrigerator appliance10. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. Controller11may include one or more proportional-integral (“PI”) controllers programmed, equipped, or configured to operate the refrigerator appliance according to example aspects of the control methods set forth herein. Accordingly, as used herein, “controller” includes the singular and plural forms.

Controller11may be positioned in a variety of locations throughout refrigerator appliance10. In the illustrated embodiment, controller11may be located e.g., behind an interface panel32or doors42or44. Input/output (“I/O”) signals may be routed between the control system and various operational components of refrigerator appliance10along wiring harnesses that may be routed through e.g., the back, sides, or mullion26. Typically, through user interface panel32, a user may select various operational features and modes and monitor the operation of refrigerator appliance10. In one embodiment, the user interface panel32may represent a general purpose I/O (“GPIO”) device or functional block. In one embodiment, the user interface panel32may include input components, such as one or more of a variety of electrical, mechanical or electro-mechanical input devices including rotary dials, push buttons, and touch pads. The user interface panel32may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. User interface panel32may be in communication with controller11via one or more signal lines or shared communication busses.

In some embodiments, one or more temperature sensors are provided to measure the temperature in the fresh food compartment12and the temperature in the freezer compartment14. For example, first temperature sensor52may be disposed in the fresh food compartment12and may measure the temperature in the fresh food compartment12. Second temperature sensor54may be disposed in the freezer compartment14and may measure the temperature in the freezer compartment14. This temperature information can be provided, e.g., to controller11for use in operating refrigerator10as will be more fully discussed below. These temperature measurements may be taken intermittently or continuously during operation of the appliance or execution of a control system as further described below.

A shelf34and wire baskets36are also provided in freezer compartment14. In addition, an ice maker38may be provided in freezer compartment14. A freezer door42and a fresh food door44close access openings to freezer and fresh food compartments14,12, respectively. Each door42,44is mounted to rotate about its outer vertical edge between an open position, as shown inFIG. 1, and a closed position (not shown) closing the associated storage compartment. In alternative embodiments, one or both doors42,44may be slidable or otherwise movable between open and closed positions. Freezer door42includes a plurality of storage shelves46, and fresh food door44includes a plurality of storage shelves48.

Referring now toFIG. 2, refrigerator appliance10may include a refrigeration system200. In general, refrigeration system200is charged with a refrigerant that is flowed through various components and facilitates cooling of the fresh food compartment12and the freezer compartment14. Refrigeration system200may be charged or filled with any suitable refrigerant. For example, refrigeration system200may be charged with a flammable refrigerant, such as R441A, R600a, isobutene, isobutane, etc.

Refrigeration system200includes a compressor202for compressing the refrigerant, thus raising the temperature and pressure of the refrigerant. Compressor202may for example be a variable speed compressor, such that the speed of the compressor202can be varied between zero (0) and one hundred (100) percent by controller11. Refrigeration system200may further include a condenser204, which may be disposed downstream of compressor202, e.g., in the direction of flow of the refrigerant. Thus, condenser204may receive refrigerant from the compressor202, and may condense the refrigerant by lowering the temperature of the refrigerant flowing therethrough due to, e.g., heat exchange with ambient air. A condenser fan206may be used to force air over condenser204as illustrated to facilitate heat exchange between the refrigerant and the surrounding air. Condenser fan206can be a variable speed fan—meaning the speed of condenser fan206may be controlled or set anywhere between and including, e.g., zero (0) and one hundred (100) percent. The speed of condenser fan206can be determined by, and communicated to, fan206by controller11.

Refrigeration system200further includes an evaporator210disposed downstream of the condenser204. Additionally, an expansion device208may be utilized to expand the refrigerant, thus further reduce the pressure of the refrigerant, leaving condenser204before being flowed to evaporator210. Evaporator210generally is a heat exchanger that transfers heat from air passing over the evaporator210to refrigerant flowing through evaporator210, thereby cooling the air and causing the refrigerant to vaporize. An evaporator fan212may be used to force air over evaporator210as illustrated. As such, cooled air is produced and supplied to refrigerated compartments12,14of refrigerator appliance10. In certain embodiments, evaporator fan212can be a variable speed evaporator fan—meaning the speed of fan212may be controlled or set anywhere between and including, e.g., zero (0) and one hundred (100) percent. The speed of evaporator fan212can be determined by, and communicated to, evaporator fan212by controller11.

Evaporator210may be in communication with fresh food compartment12and freezer compartment14to provide cooled air to compartments12,14. Alternatively, refrigeration system200may include more two or more evaporators, such that at least one evaporator provides cooled air to fresh food compartment12and at least one evaporator provides cooled air to freezer compartment14. In other embodiments, evaporator210may be in communication with any suitable component of the refrigerator appliance10. For example, in some embodiments, evaporator210may be in communication with ice maker38, such as with an ice compartment of the ice maker38. From evaporator210, refrigerant may flow back to and through compressor202, which may be downstream of evaporator210, thus completing a closed refrigeration loop or cycle.

As shown inFIG. 2, a defrost heater214may be utilized to defrost evaporator210, i.e., to melt ice that accumulates on evaporator210. Heater214may be positioned adjacent or in close proximity (e.g., below) evaporator210within fresh food compartment12or freezer compartment14. Heater214may be activated periodically; that is, a period of time ticeelapses between when heater214is deactivated and when heater214is reactivated to melt a new accumulation of ice on evaporator210. The period of time ticemay be a preprogrammed period such that time ticeis the same between each period of activation of heater214, or the period of time may vary. Alternatively, heater214may be activated based on some other condition, such as the temperature of evaporator210or any other appropriate condition.

Additionally, a defrost termination thermostat216may be used to monitor the temperature of evaporator210such that defrost heater214is deactivated when thermostat216measures that the temperature of evaporator210is above freezing, i.e., greater than zero degrees Celsius (0° C.). In some embodiments, thermostat216may send a signal to controller11or other suitable device to deactivate heater214when evaporator210is above freezing. In other embodiments, defrost termination thermostat216may comprise a switch such that heater214is switched off when thermostat216measures that the temperature of evaporator210is above freezing.

FIG. 3provides a schematic view of a heating assembly300according to exemplary embodiments of the present disclosure.FIG. 4provides a side view (e.g., partial or interrupted side view) of a heating assembly300according to additional or alternative embodiments. Heating assembly300generally includes an electrical heater301and may be used in or with any suitable refrigerator appliance as a defrost heater. For example, heating assembly300, including electrical heater301, may be used as defrost heater214in refrigeration system200to defrost evaporator210(FIG. 2). Thus, heating assembly300is discussed in greater detail below in the context of refrigerator appliance10(FIG. 1). As discussed in greater detail below, heating assembly300includes features for defrosting evaporator210while operating such that a surface temperature of heating assembly300(e.g., the temperature at an exterior surface of sheath310) is well below a maximum temperature, e.g., an auto-ignition temperature of a flammable refrigerant within evaporator210. As used herein, the term “well below” means no less than seventy-five degrees Celsius (75° C.) when used in the context of temperatures. Thus, e.g., the surface temperature of heating assembly300may be no less than one-hundred degrees Celsius (100° C.) below the auto-ignition temperature of the flammable refrigerant within evaporator210during operation of heating assembly300in certain exemplary embodiments.

As shown inFIG. 3, heating assembly300includes an electrical heater301having a sheath310formed into any suitable shape. For example, as shown inFIG. 3, sheath310may be U-shaped in certain exemplary embodiments. In alternative exemplary embodiments, sheath310may be straight, circular, arcuate, have multiple coils, etc. Sheath310may be a generally solid or non-permeable metal structure that does not permit the passage of liquids, such as water. Sheath310may be constructed of or with a suitable thermally conductive metal material. For example, sheath310may be constructed of or with aluminum or aluminum alloy material.

As shown inFIG. 3, electrical heater301extends between a first end portion302and a second end portion304. Thus, e.g., first end portion302and second end portion304of electrical heater301may each be disposed at or adjacent a respective terminal end of sheath310. Each of first end portion302and second end portion304are sealed to prevent the entry of water or moisture within sheath310. For example, electrical connections or terminals306may be positioned at one or both of first end portion302and second end portion304of electrical heater301. Optionally, electrical heater301may be coupled to an electrical power supply (not shown) at terminals306.

Electrical heater301defines an overall length (shown with dashed line L inFIG. 3) following the path defined by sheath310between the first and second end portions302,304of electrical heater301. The length L of electrical heater301may be any suitable length. For example, the length L of electrical heater301may be equal to or less than two (2) feet between each terminal306.

Turning now toFIGS. 4 through 6,FIG. 5provides a magnified view of a portion (e.g., at first end portion302) of certain embodiments of electrical heater301.FIG. 6provides a cross sectional view of electrical heater301, taken along the lines6-6. As shown, sheath310has an oppositely-disposed pair of surfaces312,314, extending along a circumferential direction C. Specifically, sheath310has an exterior surface312and interior surface314. Within sheath310, an enclosed volume316may be defined by interior surface314. In turn, exterior surface312is directed (i.e., faces) radially outward, away from enclosed volume316, while interior surface314is directed radially inward, towards enclosed volume316. Generally, enclosed volume316may be defined along the length L from first end portion302to second end portion304.

In some embodiments, various components of heating assembly300are disposed within enclosed volume316of sheath310. In particular, heating assembly300includes a resistive element or wire318that is disposed within enclosed volume316of sheath310. In other words, sheath310is disposed about resistive element318, e.g., along a circumferential direction C defined about resistive element318or length L. Resistive element318is generally configured to generate heat in response to an electrical current directed to electrical heater301, e.g., at terminals306. Resistive element318may be any suitable resistive heating element, such as a nickel chromium alloy wire.

Resistive element318may be coupled to terminals306at opposite ends of resistive element318. In some such embodiments, a discrete cold pin330A or330B may be provided at first and second end portions302,304of electrical heater301. In particular, a first end cold pin330A is in electrical communication (e.g., direct or indirect conductive communication) with resistive element318at first end portion302, and a second end cold pin330B is in electrical communication (e.g., direct or indirect conductive communication) with resistive element318at second end portion304. Both cold pins330A,330B may be positioned radially inward from sheath310(e.g., at least partially within enclosed volume316). For instance, each cold pin330A,330B may extend from a corresponding terminal306into enclosed volume316to contact resistive element318. When assembled, each cold pin330A,330B may be joined (e.g., bonded or welded) to resistive element318. Additionally or alternatively, each cold pin330A,330B may be formed from a conductive metal have a lower electrical resistance than the resistive element318. During use (e.g., active heating operations), a voltage applied across terminals306may pass between the cold pins330A,330B and resistive element318, inducing a current within resistive element318that in turn causes resistive element318to increase in temperature.

Sheath310may be packed with a thermally conductive electrical insulation319, such as magnesium dioxide or vitrified magnesite. In particular, thermally conductive electrical insulation319may be radially positioned between the resistive element318and the sheath310. As shown, thermally conductive electrical insulation319may generally separate resistive element318and sheath310along a radial direction R defined from resistive element318. Moreover, thermally conductive electrical insulation319may prevent electrical conduction between resistive element318and sheath310, while permitting heat conduction therethrough.

In some embodiments, an internal insulator320is further provided. In particular, internal insulator320is radially positioned between the resistive element318and the thermally conductive electrical insulation319. In exemplary embodiments, such as those illustrated inFIGS. 4 through 6, internal insulator320is formed as, or includes, a dielectric insulation coating applied to at least a portion of resistive element318. For instance, a suitable dielectric material (e.g., silicon-ceramic coatings; oxides of aluminum, titanium, or yttrium; etc.) may be formed or applied directly on an outer radial surface of resistive element318or cold pins330A,330B. Heat transfer between resistive element318and sheath310via internal insulator320and thermally conductive electrical insulation319may heat sheath310during operation of heating assembly300. Thus, sheath310, resistive element318, internal insulator320, and thermally conductive electrical insulation319may collectively form a Calrod® heating resistance element.

In certain embodiments, the dielectric insulation coating of internal insulator320extends across resistive element318from first end portion302to second end portion304. In turn, internal insulator320surrounds resistive element318across its full length. As illustrated, both cold pins330A,330B may be similarly surrounded by internal insulator320. In some such embodiments, internal insulator320extends continuously or uninterrupted across an outer radial surface of each cold pin330A,320B to an outer surface of resistive element318. Advantageously, internal insulator320may protect resistive element318and prevent arcing (e.g., during instances in which an unforeseen breakdown occurs within the thermally conductive electrical insulation319).

AlthoughFIGS. 4 through 6illustrate the dielectric insulation coating of internal insulator320extending across resistive element318from first end portion302to second end portion304, it is understood that alternative embodiments may provide internal insulator320across only a portion of resistive element318. For instance, other exemplary embodiments, such as those illustrated inFIG. 7, may include discrete coating segments (e.g., first and second segments326) at the first end portion302and second end portion304, respectively. Each coating segment326may extend from a corresponding terminal306continuously or uninterrupted over each cold pin330A,320B and an adjacent portion of resistive element318. An uncoated section334of resistive element318may extend between the coating segments326. Thus, the coating segments326may be spaced apart from each other along a portion of the length L between the first end portion302and the second end portion304. Advantageously, internal insulator320may protect and prevent arcing at cold pins330A,330B and adjacent portions of resistive element318(e.g., during instances in which an unforeseen breakdown occurs within the thermally conductive electrical insulation319).

Turning now toFIGS. 8 through 10, various views of portions of further exemplary embodiments of electrical heater301are provided. In particular,FIG. 8provides a side view (e.g., partial or interrupted side view) of a heating assembly300according to further exemplary embodiments.FIG. 9provides a magnified view of a portion (e.g., at first end portion302) of electrical heater301.FIG. 10provides a cross sectional view of electrical heater301, taken along the lines10-10. Except as otherwise indicated, it is understood that the exemplary embodiments ofFIGS. 8 through 10include one or more of the features of the above-described embodiments illustrated inFIGS. 1 through 7.

As an example, in some embodiments, internal insulator320is formed as or includes a dielectric sheath extending within enclosed volume316. For instance, the dielectric sheath of internal insulator320may include a rigid tube formed from, or including, a suitable dielectric ceramic (e.g., oxides of aluminum, titanium, yttrium, etc.). In certain embodiments, the dielectric sheath of internal insulator320may be radially spaced from the resistive element318or cold pins330A,330B. In other words, a predetermined radial space is defined along the radial direction R between an inner radial surface of internal insulator320and an outer radial surface of resistive element318or cold pins330A,330B. The radial space may be constant along the length L (FIG. 3) of electrical heater301. In some such embodiments, the radial space may be filled with a secondary portion of thermally conductive electrical insulation319B, while a primary portion of thermally conductive electrical insulation319A is positioned radially outward from internal insulator320(i.e., between internal insulator320and sheath310). In other embodiments, the radial space is generally empty or free of any thermally conductive insulation.

In certain embodiments, the dielectric sheath of internal insulator320extends about resistive element318from first end portion302to second end portion304. In turn, internal insulator320surrounds resistive element318across its full length. As illustrated, both cold pins330A,330B may be similarly surrounded by internal insulator320. In some such embodiments, internal insulator320extends continuously or uninterrupted over each cold pin330A,320B and resistive element318. Advantageously, internal insulator320may protect resistive element318and prevent arcing (e.g., during instances in which an unforeseen breakdown occurs within the thermally conductive electrical insulation319).

Turning now toFIGS. 11 and 12, various views of portions of still further exemplary embodiments of electrical heater301are provided. In particular,FIG. 11provides a side view (e.g., partial or interrupted side view) of a heating assembly300according to further exemplary embodiments.FIG. 11provides a magnified view of a portion (e.g., at first end portion302) of electrical heater301. Except as otherwise indicated, it is understood that the exemplary embodiments ofFIGS. 11 and 12include one or more of the features of the above-described embodiments illustrated inFIGS. 1 through 10.

In some embodiments, internal insulator320is formed as or includes a dielectric sheath extending within enclosed volume316. For instance, the dielectric sheath of internal insulator320may include a rigid tube formed from or including a suitable dielectric ceramic (e.g., oxides of aluminum, titanium, yttrium, etc.). In certain embodiments, the dielectric sheath of internal insulator320may be radially spaced from the resistive element318or cold pins330A,330B (e.g., across only a portion of resistive element318). In other words, a predetermined radial space is defined between internal insulator320and resistive element318or cold pins330A,330B. The radial space may be constant along the length L of electrical heater301that is covered by internal insulator320.

As shown, discrete sheath segments328(e.g., first and second segments) may be provided at the first end portion302and second end portion304, respectively. Each sheath segment328may extend from a corresponding terminal306to a free end322, which may be open (e.g., in the direction of the length L) to the rest of enclosed volume316. Each sheath segment328extends continuously or uninterrupted over each cold pin330A,320B and an adjacent portion of resistive element318. An uncovered section336of resistive element318may extend between the sheath segments328. Thus, the sheath segments328may be spaced apart from each other along a portion of the length L between the first end portion302and the second end portion304. Advantageously, internal insulator320may protect and prevent arcing at cold pins330A,330B and adjacent portions of resistive element318(e.g., during instances in which an unforeseen breakdown occurs within the thermally conductive electrical insulation319).