Appliance refrigeration system with final condenser   

FIELD OF THE INVENTION

The present subject matter relates generally to refrigeration systems, and more particularly to a refrigeration system with a final condenser.

BACKGROUND OF THE INVENTION

Government regulations and consumer demand strongly encourage more energy-efficient appliances, including refrigerators. Compressor-type refrigeration systems typically include a compressor, a condenser, a metering device, and an evaporator. Since these systems generally operate at relatively high ambient temperatures, a significant amount of energy is required to raise the pressure of the gas from the low-pressure side of the evaporator to the high-pressure side of the condenser.

Household refrigeration appliances, including refrigerators and freezers, typically utilize a relatively simple capillary tube type of expansion device. These tubes function as metering/restriction devices by forcing refrigerant that enters the tube to be mostly liquid, with an occasional vapor bubble. When a vapor bubble enters the capillary tube, refrigerant mass flow is greatly reduced while the bubble travels the length of the tube. The two-phase liquid/vapor refrigerant cannot be sub-cooled. Sub-cooling would provide the benefit of increasing cooling capacity by increasing the liquid fraction of the refrigerant entering the evaporator.

Sub-cooling is a common technique used in larger commercial refrigeration systems to reduce the enthalpy of the liquid refrigerant flowing from the condenser into the evaporator, thereby increasing heat absorption and overall efficiency of the system. Sub-coolers, however, are more suited for the expansion valve-type of metering/restriction devices used in the larger commercial systems and are not useful in a capillary tube-type system because the refrigerant entering the capillary tube is typically slightly two-phase. Also, sub-coolers are relatively expensive and, thus, not attractive for household consumer appliance applications.

Accordingly, it would be desirable to provide the benefits of sub-cooling to capillary tube system in a cost effective and energy efficient manner.

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In accordance with aspects of the invention, a refrigeration appliance is provided with a compression stage, a condenser stage, and an evaporation stage. The condenser stage further comprises a first condenser, for example a tube/fin condenser, and a water-cooled final condenser. The final condenser is operatively configured between the first condenser and the evaporation stage and is in communication with a water source to cool the condenser and reduce the temperature (at saturation pressure) of the refrigerant entering the evaporation stage to ambient temperature or lower.

The water source may be variously provided. For example, the water source may be condensation collection from the appliance external casing or other source, defrost drain water, or make-up water supplied to the appliance for any purpose, such as to supply chill water or to the ice maker.

The final condenser may be cooled by the water source in various ways. For example, in a particular embodiment, a water bath is configured to receive water from the water source and the final condenser, which may be a tubular configuration, is at least partially submerged in the water bath. In another embodiment, water or water vapor may be sprayed or otherwise applied directly onto the final condenser. In still a further embodiment, water from the water source may be used to wet an absorbent pad or other material that is placed near or in contact with the final condenser, wherein evaporation of the water from the pad serves to cool the final condenser.

With yet a different embodiment, a mister is disposed to disperse a water mist over the final condenser, the mister configured for receipt of water from the water source.

The appliance may employ a capillary tube as the metering device between the final condenser and the evaporator stage. A capillary tube may also connect the final condenser with the first condenser. A pressure restriction device may be operably configured in the capillary tube between the first condenser and the final condenser. This device may be, for example, a tube with a length and inner diameter selected to reduce the saturation temperature of the refrigerant from the first condenser by 5 degrees Fahrenheit or more, for example between 10 degrees to 15 degrees Fahrenheit, prior to the refrigerant entering the final condenser (wherein the saturation temperature is desirably reduced to lower than ambient temperature). In a particular embodiment, the pressure restriction device comprises a capillary tube having a length in a range of 0.5 to 2.0 inches, and an inner diameter in a range of 0.025 to 0.045 inches.

The pressure restriction device may be configured as a component of the final condenser rather than a separate component installed between the first and final condensers.

The refrigeration appliance incorporating aspects of the invention is particularly suited as a consumer refrigerator or freezer. However, it should be appreciated that the invention is not limited to these appliances. For example, the appliance may be an air conditioning unit, chiller, and so forth.

The present invention also encompasses a refrigeration system for any manner of household appliance, such as a refrigerator, freezer, air conditioning unit, chiller, and the like. The refrigeration system includes a compression stage, a condensation stage, and an evaporation stage. The condensation stage is configured in accordance with the embodiments discussed above. These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 is a schematic diagram of an exemplary refrigeration system in accordance with certain embodiments of the invention;

FIG. 2 is a schematic diagram of another exemplary refrigeration system in accordance with certain embodiments of the invention;

FIG. 3 is a schematic diagram of still a different exemplary refrigeration system in accordance with certain embodiments of the invention;

FIG. 4 is a perspective view of an exemplary refrigeration appliance that may incorporate aspects of the invention;

FIG. 5 is a back view of the machine compartment of a refrigerator incorporates of final condenser and pressure restriction device in the refrigeration system;

FIG. 6 is a view of an embodiment of a water-cooled final condenser;

FIG. 7 is a view of an alternative embodiment of a water-cooled final condenser; and

FIG. 8 is a view of still another embodiment of a water-cooled final condenser.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Referring to FIG. 1, an exemplary refrigeration system 100 for an appliance, such as a consumer refrigerator, incorporating aspects of the disclosed embodiments is illustrated. In general, the system 100 provides the benefits of refrigerant sub-cooling with minimal to no increase of power consumption of the system. The system 100 is particularly suited for a household refrigerator and, in this regard, a refrigerator 10 is depicted in FIG. 4 for sake of placing the system 100 in a desired working environment. Referring to FIG. 4, the refrigerator 10 has an outer casing 12 that defines a top 24, sides 26, and a bottom 28 that define an upper fresh food compartment 14 with a frontal access opening through doors 16 and 18, and a lower freezer compartment 20 a frontal access opening through door 22. An ice/water dispenser 30 is configured in the door 18 of the fresh food compartment 14. The type of refrigerator depicted in FIG. 1 is generally referred to as a French-style refrigerator wherein the fresh food compartment 14 is configured above the freezer compartment 20 and includes two French doors 16, 18. In an alternate embodiment, a single door can be used instead of the dual doors 16, 18. It should be appreciated that the present invention is not limited to any particular type or style of refrigerator, and that the refrigerator 10 depicted in FIG. 1 is for illustrative purposes only.

Although the aspects of the invention will generally be described herein with respect to a refrigerator, it should be appreciated that the system 100 can be applied to any refrigeration system or appliance utilizing a capillary tube expansion system, including for example, a household air conditioning system.

As is shown in FIG. 1, the refrigeration system 100 includes an evaporation stage 112 (with an evaporator 102), a compression stage 114 (with a compressor 104) disposed downstream of the evaporation stage 112, and a condenser stage 116 (with a first condenser 106) disposed downstream of the compression stage 114. The refrigeration system includes therein a working medium (i.e., the refrigerant).

The compression stage 114 is generally configured to compress the refrigerant received in a low-pressure vapor state from the evaporation stage 112 into a high-pressure gas vapor. The compression stage 114 can generally comprise any conventional compressor unit. From the compression stage 114, the high-pressure refrigerant gas passes via line 105 to the condenser stage 116 where the refrigerant is condensed and heat is rejected to the ambient air. In this embodiment, the condenser stage 116 includes the first condenser 106, which may be an air-cooled condenser, water-cooled condenser, or any other type of conventional condenser unit. The high pressure liquid refrigerant from the condenser stage 116 travels to the evaporation stage 112 via line 111, where the low-pressure liquid refrigerant is vaporized to absorb heat. Line 111 is typically a capillary tube that provides restriction to turn the high pressure liquid refrigerant into a low pressure mixture of liquid and vapor refrigerant. Line 111 typically exchanges heat with line 103, which improves the cooling cycle performance. From the evaporation stage 112, the refrigerant is conveyed to the compression stage 114 via line 103.

In certain embodiments, the system 100 may include a condenser loop 120 downstream of the condenser 106. The condenser loop 120 generally comprises a length of tubing that is placed near cold areas of the refrigerator doors to keep these areas from sweating, particularly when humidity is high.

Referring again to FIG. 1, the condenser stage 116 includes a water-cooled final condenser 110 operatively configured between the first condenser 106 and the evaporation stage 112. The final condenser 110 is in communication with a water source 118 to cool the final condenser and reduce the temperature (at saturation pressure) of the refrigerant entering the evaporation stage 112 to ambient temperature or lower. The water-cooled final condenser 110 will be described in greater detail below.

The refrigerant passes through line 109 to final condenser 110 where it is cooled before the refrigerant passes through line 111 to the evaporator 102. The low-pressure liquid line 111 extends from the final condenser 110 to the evaporator 102 where the refrigerant is vaporized to absorb heat. In one embodiment, the line 111 is a length of capillary tubing. The length of the line 111 can be up to approximately 5 feet, and have, for example, an inner diameter in the range of approximately 0.020 to 0.032 inches or larger. In accordance with the aspects of the disclosed embodiment, when the cooled refrigerant enters the evaporator 102 from the final condenser 110, it is at a lower enthalpy. This lower enthalpy allows the refrigerant to absorb more heat in the evaporator 102. Because the conditions at the compressor 104 are unchanged, the compressor power is not changed. However, the cooling capacity is increased, resulting in a decrease in overall energy usage.

Referring to FIGS. 2 and 3, the refrigeration system 100 may also include a restriction device 108 placed after the first condenser 106 and before the final condenser 110. The liquefied refrigerant passes from the condenser 106 through the line 107 to the restriction device 108, which is configured to reduce the pressure of the refrigerant leaving the condenser 106 and entering the final condenser 110. This process will reduce the saturation temperature of the refrigerant down from the condensing temperature of the first condenser 106, which is typically in the range of approximately 10 to 15 degrees Fahrenheit above the ambient temperature. In one embodiment, the restriction device 108 comprises a piece of capillary tubing. Generally, the restriction device 108 has a very short length, such as in the range of approximately 0.5 to 2.0 inches, and preferably approximately 1.0 inch. An inner diameter of the restriction device 108 can be in the range of approximately 0.025 to 0.045 inches, and preferably 0.035 inches or less. In alternate embodiments, the restriction device 108 can be of any suitable size that will enable the reduction of the temperature of the refrigerant leaving the condenser 106 and entering the final condenser 110 by approximately 10 to 15 degrees Fahrenheit in saturation pressure, without concern for a mixture of liquid and vapor refrigerant entering the evaporation stage 102. The restriction device 108 is generally made from a material such as copper or steel.

Typically, the temperature of the refrigerant exiting the condenser 106 will be in the range of approximately 100 to 105 degrees Fahrenheit when the appliance is operated in a 90 degree Fahrenheit ambient. By adding the restriction device 108 between the condenser 106 and the final condenser 110, the saturation temperature of the refrigerant is reduced from the condensing temperature down to about ambient temperature.

FIG. 3 illustrates another example of a cooling system 100 wherein the restriction device is incorporated with the final condenser in a combination 118. In this embodiment, the final condenser 118 may comprise a section of small diameter tubing, such as a capillary tube, that is suitably sized to provide the required pressure drop to achieve a reduction in temperature. Generally, a pressure drop of approximately 20 psi will reduce the saturation temperature of R-134 type refrigerant approximately 10 degrees Fahrenheit, from approximately 100 degrees Fahrenheit to approximately 90 degrees Fahrenheit.

Referring to FIGS. 1 through 3 in general, the refrigerant final condenser 110 is placed after the condenser 106 to further reduce the temperature of the refrigerant prior to entering the evaporator 102. The final condenser 110/118 is generally compatible with capillary tube type expansion devices typically found in consumer appliances, such as household refrigerators. In one embodiment, the final condenser 110/118 comprises a tube have a internal diameter of approximately 0.08 inches, or generally in the range of approximately 0.02 inches to 0.10 inches. A length of the tube can be in the range of approximately ten to twenty feet. The tube may be variously configured, for example in a flat looped configuration, spiral configuration, or any other suitable shape or configuration depending on system requirements and space considerations.

The final condenser 110/118 is water-cooled to desirably drop the temperature of the refrigerant to below ambient temperature. When this cooled refrigerant enters the capillary tube (between the final condenser and evaporator 102), it is at a lower enthalpy, which allows the refrigerant to absorb more heat in the evaporator 102. Because the conditions at the compressor 104 are unchanged, the power consumed by the compressor is not increased. It is estimated that the cooling capacity of the system 100 can be increased by as much as 10% for the same power usage.

The water source 118 may be variously configured. For example, the water source may be condensation collected from the appliance external casing, defrost drain water, or make-up water supplied to the appliance for any purpose, such as to supply chill water or ice making capabilities. The water source 118 may be a reservoir that is periodically or continuously filled with make-up water.

FIG. 5 depicts a machinery compartment 122 of a refrigerator 10 wherein components of the refrigeration system are typically housed, such as the compressor 104 and first condenser 106 (depicted in this embodiment as a coiled tubular/wire heat exchanger). A fan 136 may be utilized to draw air through the first condenser 106. The final condenser 110 may also be located in the machinery compartment 122 upstream of the evaporator 102, which is typically placed inside the refrigerated cabinet. The final condenser 100 is depicted in this embodiment as a tubular heat exchanger that is formed into a flat loop configuration and at least partially submerged in a water bath 124, as also depicted in FIG. 7. The water bath 124 may be any suitable container or vessel that is supplied with water from the water source 118, which may be a reservoir that is supplied with make-up water, condensation water, defrost drain water, and so forth. The flat loop configuration of FIG. 7 may be desired for the water bath embodiment in that the entire final condenser 100 can be submerged in a relatively low profile water bath 124.

Referring to FIG. 7, it may be desired to provide automatic controls for the water bath 124. For example, a level sensor 132 may be disposed within the bath 124 and configured with a controllable valve 134 that opens to fill the water bath 124 to a certain level when the water level drops to the actuation level of the sensor 132.

FIG. 6 depicts an embodiment wherein the final condenser 110 is a tubular heat exchanger formed into a coil that resides within a water bath 124. Only a portion of the coil is actually submerged in the water within the water bath 124. A mister 126 is provided to direct water or water vapor onto the exposed portions of the final condenser 110. A controllable valve 134 is provided to pass water from the water source into a header 128. Nozzles 130 are provided in the header 128 to direct a spray or mist onto the coiled final condenser 110. In this embodiment, the water source 118 may be a pressurized water line.

FIG. 8 depicts an embodiment wherein the final condenser 110 is a tubular heat exchanger formed into a coil, as in FIG. 7. An absorbent material pad 138 is disposed within the coil as is wetted with water from the nozzles 130. This pad 138 may be, for example, a sponge, absorbent web, and so forth. The water from the nozzles 130 cools the final condenser 110, and the cooling process is supplemented with evaporation of water from the absorbent pad 138. The nozzles 130 may be intermittently actuated by the valve 134 to the extent necessary to maintain the wetted condition of the material 138.

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.