The present subject matter relates generally to sealed systems for appliances, such as refrigerator appliances, and methods for defrosting evaporators of sealed systems.
Refrigerators generally include a cabinet that defines a chilled chamber. The chilled chamber is commonly cooled with a sealed system having an evaporator. One problem frequently encountered with modern refrigerators 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 to heat the evaporator when the evaporator is not operating.
Suitably defrosting the evaporator with the heater is difficult. For example, heaters can be large energy consumers and can negatively affect the energy efficiency of the refrigerator during long defrosts. In addition, the heater can raise the temperate of the adjacent chilled chamber during long defrosts, and high chilled chamber temperatures can lead to freezer burn and other negative effects. Radiant heaters can also be unsuitable for sealed systems charged with organic, flammable refrigerants due to temperature exposure requirements for such sealed systems. The temperature limits imposed on sealed systems charged with flammable refrigerant can make defrosting an evaporator with a radiant heater impractical.
Accordingly, a sealed system with features for effectively and efficiently defrosting an evaporator would be useful. In addition, a method for effectively and efficiently defrosting an evaporator would be useful.
The present subject matter provides a sealed system for an appliance. The sealed system includes a compressor operable to generate a flow of compressed refrigerant, an evaporator and a drain trough disposed below the evaporator. A bypass conduit fluidly couples a bypass valve and the evaporator. The bypass valve is configured for selectively directing refrigerant from a condenser around an expansion device to the evaporator via the bypass conduit. A portion of the bypass conduit is positioned at and connected to the drain trough. A related method for defrosting an evaporator is also provided. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.
In a first exemplary embodiment, a sealed system for an appliance is provided. The sealed system includes a compressor operable to generate a flow of compressed refrigerant. A condenser is disposed downstream of the compressor such that the condenser receives the flow of compressed refrigerant from the compressor during operation of the compressor. A fan is positioned proximate the condenser and operable to generate a flow of air across the condenser. The sealed system also includes an expansion device and an evaporator. A drain trough is disposed below the evaporator. A bypass valve is disposed downstream of the condenser. A bypass conduit fluidly couples the bypass valve and the evaporator. The bypass valve is configured for selectively directing refrigerant from the condenser around the expansion device to the evaporator. A portion of the bypass conduit is positioned at and connected to the drain trough.
In a second exemplary embodiment, a method for defrosting an evaporator within an appliance is provided. The method includes running a compressor of the appliance during a condenser preheat. A condenser fan of the appliance is deactivated during the condenser preheat such that a temperature of a condenser of the appliance increases while the compressor is running during the condenser preheat. The method also includes actuating a bypass valve of the appliance such that refrigerant from the condenser bypasses an expansion device of the appliance and flows to the evaporator and running the compressor during an evaporator defrost. The temperature of the condenser decreases while the compressor is running during the evaporator defrost.
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.
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.
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.
In the exemplary embodiment shown in
Within refrigeration system 60, refrigerant flows into compressor 64, which operates to increase the pressure of the refrigerant. This compression of the refrigerant raises its temperature, which is lowered by passing the refrigerant through condenser 66. Within condenser 66, heat exchange with ambient air takes place so as to cool the refrigerant. A condenser fan 72 is used to pull air across condenser 66, as illustrated by arrows AC, so as to provide forced convection for a more rapid and efficient heat exchange between the refrigerant within condenser 66 and the ambient air. Thus, as will be understood by those skilled in the art, increasing air flow across condenser 66 can, e.g., increase the efficiency of condenser 66 by improving cooling of the refrigerant contained therein.
An expansion device (e.g., a valve, capillary tube, or other restriction device) 68 receives refrigerant from condenser 66. From expansion device 68, the refrigerant enters evaporator 70. Upon exiting expansion device 68 and entering evaporator 70, the refrigerant drops in pressure. Due to the pressure drop and/or phase change of the refrigerant, evaporator 70 is cool relative to compartments 14 and 18 of refrigerator appliance 10. As such, cooled air is produced and refrigerates compartments 14 and 18 of refrigerator appliance 10. Thus, evaporator 70 is a type of heat exchanger which transfers heat from air passing over evaporator 70 to refrigerant flowing through evaporator 70. An evaporator fan 74 is used to pull air across evaporator 70 and circulated air within compartments 14 and 18 of refrigerator appliance 10.
Collectively, the vapor compression cycle components in a refrigeration circuit, associated fans, and associated compartments are sometimes referred to as a sealed refrigeration system operable to force cold air through compartments 14, 18 (
During operation of refrigeration system 60, water vapor in compartments 14 and 18 of refrigerator appliance 10 may condense onto evaporator 70 and form frost buildup on evaporator 70. Overtime, frost accumulation on evaporator 70 can negatively affect performance of evaporator 70. Thus, refrigeration system 60 includes features for defrosting evaporator 70. In particular, refrigeration system 60 includes features for fully and/or efficiently defrosting evaporator 70 relative to known systems that expose evaporators to radiant heating elements during defrosts. Such features of refrigeration system 60 are discussed in greater detail below in the context of
As shown in
Bypass valve 80 is disposed downstream of condenser 66. Thus, refrigerant from condenser 66 flows to bypass valve 80 within refrigeration system 60 during operation of compressor 64. As an example, bypass valve 80 may be a two-way valve, such as a two-way solenoid valve. As another example, bypass valve 80 may be a three-way valve, such as a three-way solenoid valve. Bypass conduit 82 fluidly couples bypass valve 80 and evaporator 70 such that refrigerant at bypass valve 80 may flow through bypass conduit 82 to evaporator 70. As an example, bypass conduit 82 may be (e.g., aluminum or copper) tubing or piping that extends from bypass valve 80 to an inlet of evaporator 70. Thus, bypass valve 80 and evaporator 70 may be in direct fluid communication with each other via bypass conduit 82.
Bypass valve 80 is selectively adjustable between a normal operating configuration and a bypass operating configuration. In the normal operating configuration, refrigerant from condenser 66 flows through bypass valve 80 to expansion device 68 during operation of compressor 64. Thus, refrigerant flows through refrigeration system 60 in the manner described above with reference to
Refrigerant at an inlet of evaporator 70 is hotter when bypass valve 80 is in the bypass operating configuration compared to when bypass valve 80 is in the normal operating configuration. Thus, refrigerant delivered to evaporator 70 via bypass conduit 82 may flow into evaporator 70 and heat evaporator 70 after shifting bypass valve 80 from normal operating configuration to the bypass operating configuration. By heating evaporator 70, the refrigerant within evaporator 70 melts ice on an outer surface of evaporator 70 and thereby defrosts evaporator 70. Thus, bypass valve 80 and bypass conduit 82 may assist with defrosting evaporator 70 by bypassing refrigerant flow around expansion device 68 and delivering refrigerant that is hotter than the freezing temperature of water into evaporator 70. As an example, when bypass valve 80 is in the bypass operating configuration, refrigerant entering evaporator 70 from bypass conduit 82 may have a temperature no less than sixty degrees Celsius (60° C.). Heat may be evenly distributed through evaporator 70 via refrigerant during defrost cycles when bypass valve 80 is in the bypass operating configuration. In contrast, standard defrosting methods utilizing radiant heating elements adjacent an associated evaporator heat only areas of the associated evaporator that are in line-of-sight of the radiant heating element or in contact with the radiant heating element.
As shown in
Drain trough 90 may be sized to assist with collecting liquid runoff from evaporator 70. For example, an area or footprint of drain trough 90, e.g., in a plane that is perpendicular to vertical, may be larger than a corresponding area or foot print of evaporator 70. In particular, drain trough 90 defines a length L. The length L of drain trough 90 may be larger than a corresponding length of evaporator 70 such that drain trough 90 is larger than and extends past evaporator 70.
At least a portion of bypass conduit 82 may also be positioned at and connected to drain trough 90. Thus, bypass conduit 82 and drain trough 90 may be in conductive thermal communication with each other. As an example, a portion of bypass conduit 82 may be brazed or soldered to drain trough 90. As another example, a portion of bypass conduit 82 may be clipped, fastened, adhered or otherwise mounted to drain trough 90. By connecting bypass conduit 82 to drain trough 90, heat transfer between bypass conduit 82 and drain trough 90 may assist with melting ice within drain trough 90 thereby assisting with proper operation of drain trough 90. In certain exemplary embodiments, bypass conduit 82 is positioned on and contacts drain trough 90 along the length L of drain trough 90 in order to increase heat transfer between bypass conduit 82 and drain trough 90.
As discussed above, bypass conduit 82 may be tubing or piping. In certain exemplary embodiments, bypass conduit 82 may be metal tubing, such as copper or aluminum tubing, having a circular cross-section along a length of the metal tubing. Thus, bypass conduit 82 may define an internal diameter, and the internal diameter of bypass conduit 82 may be constant. The internal diameter of bypass conduit 82 may be selected to match adjacent sections of tubing or piping within refrigeration system 60. For example, the internal diameter of bypass conduit 82 may be selected to match an exit line of condenser 66 and/or an inlet line of evaporator 70. In such a manner, a pressure drop of refrigerant within bypass conduit 82 between condenser 66 and evaporator 70 when bypass valve 80 is in the bypass operating configuration may be limited or reduced.
Refrigeration system 60 also includes an electric heating element 94, such as a resistance heating element, in certain exemplary embodiments. Heating element 94 is positioned on and/or mounted to bypass conduit 82. Thus, when activated, heating element 94 may heat bypass conduit 82 and refrigerant within bypass conduit 82. In certain exemplary embodiments, heating element 94 may be encased within foam insulation of refrigerator 10, e.g., in a wall of casing 12. Thus, heating element 94 may be spaced apart from evaporator 70, e.g., such that refrigeration system 60 does not include an electric heating element disposed at or exposed to an outer surface of evaporator 70. Such positioning of heating element 94 can allow heating element 94 to increase a temperature of refrigerant entering evaporator 70 during defrost cycles while also limiting an operating temperature of heating element 94, as discussed in greater detail below.
Refrigeration system 60 may be charged with a flammable refrigerant, such as a flammable alkane, hydrocarbon or organic compound. As another example, the flammable refrigerant may be R600a. When charged with flammable refrigerant, a maximum operating temperature of components within refrigerator appliance 10 may be limited to no more than a maximum temperature, e.g., six hundred and eighty degrees Fahrenheit (680° F.). By positioning heating element 94 in contact with bypass conduit 82, heat transfer between heating element 94 and bypass conduit 82 may be both radiant heat transfer and conductive heat transfer, and the maximum operating temperature of heating element 94 may be no greater than six hundred and eighty degrees Fahrenheit while heating element 94 operates to heat refrigerant entering evaporator 70 during defrost cycles. In addition, positioning heating element 94 within foam insulation may remotely position heating element 94 relative to evaporator 70 such that heating element 94 is remotely positioned relative to a space where refrigerant can collect within refrigerator 10.
Components of refrigeration system 60 may also be operated to assist defrosting of evaporator 70. For example, condenser fan 72 may be configured to deactivate whenever bypass valve 80 is in the bypass operating configuration and bypass valve 80 directs refrigerant from condenser 66 around expansion device 68 to evaporator 70. In particular, a defrost cycle according to the present subject matter may include a condenser preheat portion and an evaporator defrost portion, e.g., that are performed sequentially. Compressor 64 runs during the condenser preheat portion of the defrost cycle. In addition, bypass valve 80 is in the normal operating configuration and condenser fan 72 is deactivated during the condenser preheat portion of the defrost cycle. Thus, a temperature of condenser 66 increases while compressor 64 is running during the condenser preheat. By deactivating condenser fan 72 and reducing convective heat transfer between condenser 66 and ambient air about condenser 66, condenser 66 may function as a thermal capacitor during the condenser preheat portion of the defrost cycle and thereby provide thermal energy to other components of refrigeration system 60 during later portions of the defrost cycle, as discussed in greater detail below.
After the condenser preheat portion of the defrost cycle, bypass valve 80 shifts or actuates from the normal operating configuration to the bypass operating. Thus, after increasing the temperature of condenser 66 during the preheat portion of the defrost cycle, bypass valve 80 actuates to the bypass operating configuration such that refrigerant from condenser 66 bypasses expansion device 68 and flows to evaporator 70 via bypass conduit 82.
After actuating bypass valve 80 to the bypass operating configuration, compressor 64 runs during the evaporator defrost portion of the defrost cycle. As discussed above, the temperature of condenser 66 increases while compressor 64 is running during the condenser preheat. Conversely, the temperature of condenser 66 decreases while compressor 64 is running during the evaporator defrost portion of the defrost cycle. In particular, heat transfer between condenser 66 and refrigerant within condenser 66 may increase the temperature of refrigerant exiting condenser 66, and the heated refrigerant from condenser 66 may flow to evaporator 70 via bypass conduit 82 in order to defrost evaporator 70, as discussed above. In such a manner, the mass of condenser 66 may provide thermal storage for later portions of the defrost cycle. Condenser fan 72 may also be deactivated during the evaporator defrost portion of the defrost cycle in order to limit heat transfer between condenser 66 and ambient air about condenser 66. Further, heating element 94 may be activated during the evaporator defrost portion of the defrost cycle in order to heat refrigerant within bypass conduit 82.
Defrosting evaporator 70 in the manner discussed above can have numerous potential benefits. For example, evaporator 70 may be defrosted more efficiently using refrigerant from condenser 66 compared to systems using radiant heating elements to defrost an evaporator. In addition, heating element 94 may be positioned at and operate in an area with reduced risk for flammability of an organic compound. Further, defrosting without an exposed radiant heating element in freezer compartment 18 can reduce or eliminate freezer burn on food items stored in the freezer compartment 18.
Conduit 100 also extends between or includes a top portion 103 and a bottom portion 105. Top portion 103 and bottom portion 105 of conduit 100 may be spaced apart from each other, e.g., along a vertical direction V. In particular, top portion 103 of conduit 100 may be positioned above bottom portion 105 of conduit 100, e.g., along the vertical direction V. Inlet 102 and outlet 104 of conduit 100 may both be positioned at or adjacent top portion 103 of conduit 100.
Conduit 100 may be bent or formed into any suitable shape. For example, as shown in
Conduit 100 may also include a pair of jumper tubes, each positioned at a respective one of inlet 102 and outlet 104 of conduit 100. The jumper tubes may assist with coupling evaporator 70 to other components of refrigeration system 60. For example, as discussed above, conduit 100 may include aluminum tubing between inlet 102 and outlet 104 of conduit 100. In contrast, the jumper tubes may be copper tubing. Copper tubing can be significantly easier to join together with solder compared to aluminum tubing. Thus, the jumper tubes may facilitate connection of evaporator 70 into refrigeration system 60 by providing a connection point to adjacent tubing. For example, bypass conduit 82 may be coupled to the jumper tube at inlet 102 of conduit 100.
Conduit 100 also defines an outer surface 106. A spine fin heat exchanger 110 is wound onto conduit 100 at outer surface 106 of conduit 100. In particular, spine fin heat exchanger 110 may form a helix on outer surface 106 of conduit 100. Spine fin heat exchanger 110 assist with heat transfer between air passing over evaporator 70 and refrigerant flowing through conduit 100, e.g., by increasing a heat exchange surface exposed to the air about evaporator 70.
As shown in
Plate fins 124 may be mounted to bypass conduit 82 at second section 122 of bypass conduit 82. For example, second section 122 of bypass conduit 82 may be bent into a serpentine pattern, and plate fins 124 may extend between windings or coils of second section 122 of bypass conduit 82. Plate fins 124 assist with heat transfer between air passing over bypass conduit 82 and refrigerant flowing through second section 122 of bypass conduit 82, e.g., by increasing a heat exchange surface exposed to the air about bypass conduit 82. Plate fins 124 also may further assist with limiting ice accumulation between evaporator 70 and drain trough 90.
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.