US20090293514A1

US20090293514A1 - Cooling system for refrigerator

Info

Publication number: US20090293514A1
Application number: US12/131,595
Authority: US
Inventors: Brent Alden Junge
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2008-06-02
Filing date: 2008-06-02
Publication date: 2009-12-03

Abstract

A cooling system for a refrigerator having a fresh food compartment and a freezer compartment separated by a partition, includes a compressor for compressing a refrigerant; a condenser for condensing the compressed refrigerant; an evaporator having a freezer compartment portion and a fresh food compartment portion; wherein the freezer compartment portion of the evaporator cools a freezer compartment, and the fresh food compartment portion of the evaporator cools a fresh food compartment. The fresh food compartment portion of the evaporator projects into a passage formed in the partition which passage extends between the fresh food compartment portion of the evaporator and the fresh food compartment.

Description

BACKGROUND OF THE DISCLOSURE

Refrigerators can have a single evaporator or a two evaporator cooling system. In typical single-evaporator refrigerators, since the freezer compartment and the fresh food compartment are simultaneously cooled with one evaporator, the temperature of the evaporator must be maintained at a temperature lower than about −18° C., which is typically the temperature of the freezer compartment. Accordingly, an evaporator is used with a lower temperature than is necessary is used to cool the fresh food compartment, causing the efficiency of the overall system to be relatively low.
In a typical two evaporator refrigerator, cool air of the freezer compartment and that of the fresh food compartment are completely separated, and a separate evaporator is provided in both the freezer compartment and the fresh food compartment. Since an additional evaporator is needed, however, the manufacturing cost of the refrigerator is increased and the capacity of the refrigerator is reduced. Accordingly, there is a need for providing an evaporator system in which benefits of the two evaporator system are provided with using a single evaporator.

BRIEF DESCRIPTION OF THE DISCLOSURE

The present disclosure relates to a refrigerator with a single integrally formed evaporator a portion of which provides cooling for the freezer compartment and a portion of which provides cooling for the fresh food that provides many of the advantages of a dual evaporator system while retaining the advantages of a single evaporator system.
Since the fresh food evaporator and the freezer evaporator are part of a single integrally formed evaporator, the evaporator is cost efficient since it uses less material. The evaporator also increases reliability of the system since it reduces the number of tubing joints and valves. The evaporator also increases available space by using space between the fresh food and freezer compartments instead of space in the fresh food compartment for the second evaporator. The evaporator also is energy efficient by allowing the fresh food evaporator portion to operate in a higher temperature environment and allowing the fresh food evaporator portion to be defrosted using the fresh food fan instead of adding resistance heat. Separate cooling air streams for the fresh food and freezer compartments also allow for higher humidity in the fresh food compartment and less humidity in the freezer compartment, than would be the case with a conventional single evaporator system.
An evaporator system for a refrigerator includes a compressor for compressing a refrigerant; a condenser for condensing the compressed refrigerant while cooling the refrigerant; an evaporator compartment having a freezer compartment evaporator and a fresh food compartment evaporator; wherein the fresh food evaporator is a portion of the freezer evaporator. The system further comprises a freezer evaporator fan and fresh food evaporator fan. When cooling the freezer compartment the freezer fan moves the relatively lower temperature freezer cooling air stream over the freezer evaporator portion which evaporates the refrigerant to cool a freezer compartment. When cooling only the fresh food compartment, only the fresh food evaporator fan is energized, moving the relatively higher temperature fresh food cooling air stream over the fresh food evaporator portion which evaporates refrigerant to cool a fresh food compartment. Since the fresh food airflow temperature is warmer than the freezer airflow temperature, the overall evaporator temperature is warmer and the refrigerant pressure is higher than when cooling the freezer compartment, resulting in improved energy efficiency, relative to a typical two evaporator system. The fresh food compartment portion of the evaporator extends into a passage formed between the freezer compartment and the fresh food compartment which passage is in fluid flow communication with the fresh food compartment to provide cooling air from the fresh food compartment portion of the evaporator.
A refrigerator includes a freezer compartment; a fresh food compartment; a compressor for compressing a refrigerant; a condenser for condensing the compressed refrigerant while cooling the refrigerant; an evaporator having a first portion for cooling air delivered to the freezer compartment; and a second portion for cooling air delivered to the fresh food compartment, wherein the first and second portions are integral with each other.
A method for evaporating refrigerant to cool freezer and fresh food compartments of a refrigerator, includes the steps of providing a compressor for compressing the refrigerant; providing a condenser for condensing the compressed refrigerant; providing an evaporator which has a first portion for evaporating refrigerant to cool the freezer compartment and a second portion for evaporating refrigerant to cool the fresh food compartment, wherein the first portion and the second portion are integral.
One aspect of the disclosure is an improvement in food preservation by obtaining the benefit of using two evaporators with a single evaporator. The cooling capacity of the fresh food compartment is increased due to the extra surface area of the evaporator within the fresh food compartment.
Another aspect of the disclosure is the greater internal volume in the fresh food compartment, since the evaporator is formed in the freezer compartment.
Another aspect of the disclosure is the ability to maintain cooling in high humidity applications because the evaporators are not blocked by frost.
Another aspect of the disclosure is that no additional tubing or joints are used which minimizes potential leaks. An energy savings is achieved, since the fresh food evaporator runs at higher pressure, and defrosting can be accomplished using fan only.
Still another aspect of the disclosure is a reduction in components required, such as a separate second evaporator, tubing and joints. Still other aspects of the disclosure w ill become apparent upon a reading and understanding of the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a refrigerator having side by side freezer and refrigeration compartments;

FIGS. 2 and 3 illustrate a refrigerator having a first and second evaporator in a series configuration where the first evaporator can be bypassed by way of a valve;

FIG. 4 illustrates a schematic diagram of a first and second evaporator in a series configuration;

FIG. 5 illustrates a schematic diagram of a first and second evaporator in a parallel configuration;

FIG. 6 illustrates a schematic diagram of a first and second evaporator in a parallel configuration;

FIG. 7 illustrates a schematic diagram of a single component two evaporator system in accordance with the present disclosure;

FIG. 8 illustrates a side by side refrigerator with the single component two evaporator system of FIG. 7;

FIG. 9 illustrates a side elevational view of a passageway of the single component two evaporator system of FIG. 8; and

FIG. 10 illustrates a chart listing several states of operation for the two evaporator system of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 illustrates a cabinet of a refrigerator 10 with a fresh food chamber 12 and a freezing chamber 14. Two evaporator systems are not very common within the U.S. FIGS. 4 and 6 depict the most common types used here.
As shown in FIGS. 2 and 3, a direct cooling type refrigerator 16 has a refrigerating cycle in which two evaporators 20 and 22 are connected in series. A compressor 24 compresses refrigerant of a refrigerating cycle. A condenser 26 receives compressed refrigerant in a direction 27 along a refrigerant passage and condensing the refrigerant while emanating heat. A first evaporator 20 used for a fresh food compartment 21 is attached on a rear surface of the refrigerating chamber and cools the refrigerating chamber by evaporating the refrigerant from the condenser 26. A second evaporator 22 used for a freezer compartment 23 is attached on a rear surface of the freezing chamber and is connected with the first evaporator in series in order to evaporate the refrigerant from the first evaporator to thus cool the freezing chamber, and a valve or restrictor 30 selectively opens a first tube 32 that connects the condenser and the first evaporator and a second tube 34 that connects the condenser and the second evaporator.
In this configuration of two evaporators in series, when a hot food item is received in the refrigerating chamber, for example, an increase in temperature within the refrigerating chamber is detected and a refrigerant is controlled to circulate in the first evaporator to cool the refrigerating chamber. Even if the freezing chamber has been sufficiently cooled, the refrigerant is also circulated in the second evaporator of the freezing chamber. Thus, the freezing chamber will be unnecessarily overcooled while the refrigerating chamber may not be sufficiently cooled because of the additional unnecessary burden of cooling the freezing chamber.
The configuration of evaporators shown in FIGS. 2 and 3 is typically used in direct cool type refrigerator designs where no air circulation fans are provided. In this type of design, cooling is provided to a compartment whenever refrigerant is supplied to the evaporator within the compartment.
FIG. 4 depicts a two evaporator system in series without a valve to allow refrigerant to bypass the first evaporator. This type of system is typically used in systems where heat is transferred using cooling fans. The cooling in either compartment can be reduced by turning off the respective cooling fan. A regulator valve or restrictor 36 is used for regulating pressure of the refrigerant which has passed through the second evaporator 22 at the outlet of the second evaporator. Thus, the first evaporator 20 cools the refrigerating chamber of the refrigerator, and the second evaporator 22 cools the freezing chamber of the refrigerator.
Problems with the evaporator series configuration include an increase in cost, due to the additional components required which include an additional evaporator, drain pan, fan motor, air ducts and evaporator cover, additional tubing connections, several additional joints, and a loss of internal volume, as much as half a cubic foot decrease in storage volume.
A refrigerator with a parallel type refrigeration circuit is shown in FIGS. 5 and 6. This refrigerator has a refrigerating circuit in which the two evaporators 40 and 42 are connected in parallel. In the refrigerating cycle, a compressor 44 compresses the refrigerant. A condenser 46 receives the compressed refrigerant and condenses the refrigerant. The first evaporator 40 used for the freezer compartment is typically located in a lower rear area of the freezer chamber and cools air for circulation through the freezer chamber by evaporating the refrigerant received from the condenser as it passes through the evaporator. The second evaporator 42 is typically located in a lower rear area of the fresh food chamber and connected to evaporate the refrigerant received from the condenser to thus cool the air for circulation through the fresh food chamber. A valve 54 selectively opens a first tube 50 that connects the condenser and the first evaporator and a second tube 52 that connects the condenser and the second evaporator. Regulator valves or restrictors 56, 58 are used for regulating pressure of the refrigerant entering the first and second evaporators 40, 42. A check valve 48 is often used to prevent refrigerant migration into the freezer evaporator. When the first and second evaporators 40, 42 are connected in parallel, either one or both of the evaporators can be selected.
Several problems with the parallel evaporator system described above include the requirement for additional components such as a second evaporator, drain pan, fan motor, air ducts and evaporator cover. A solenoid valve or valves and a check valve to prevent refrigerant migration are also needed. Additional tubing connections and approximately ten additional joints are needed. A loss of internal volume as such is as much as half a cubic foot decrease in storage volume can also occur.
Referring now to FIGS. 7-9. in accordance with one aspect of the present disclosure, a refrigerator 60 includes an outer cabinet 62 containing a freezer compartment 64 and fresh food compartment 66. A compressor 67 compresses refrigerant and a condenser 68 receives compressed refrigerant and condenses the refrigerant. A regulator valve or restrictor 69 is used to regulate pressure of the refrigerant entering the evaporator 71. The freezer compartment 64 is maintained at sub-freezing temperatures and the fresh food compartment 66 is kept at above freezing temperatures.
Food preserving temperatures are achieved by circulating air through these compartments and over evaporator 71 positioned in a vertically disposed evaporator housing 70 positioned in the lower region of the freezer compartment and formed by a wall structure 73.
Referring to FIG. 8, in accordance with the present disclosure, a single evaporator 71 includes a portion 72 dedicated to cooling the freezer compartment, enclosed in housing 70, which is contained within the freezer compartment, and a portion 74 dedicated to cooling the fresh food compartment, which extends from the freezer compartment into a cavity 88 formed within the mullion or partition 76 between the freezer and fresh food compartments formed in part by partition side walls 76 a and 76 b to receive evaporator portion 74 and provide an airflow path from evaporator portion 74 to the interior of the fresh food compartment. There is no need to selectively switch refrigerant flow between the evaporator portions 72 and 74, since refrigerant fluid flows through both sections simultaneously.
The evaporator 71 comprises a serpentine tube array. Evaporator portion 74 is formed by a fold or bend in the tubing to extend the evaporator second portion into cavity 88. This cavity is thermally isolated from the freezer compartment to reduce heat transfer from the fresh food compartment and to minimize any air exchange. The thermal isolation is provided by insulation in the mullion separating the freezer compartment and the fresh food compartment which substantially surrounds cavity 88. Thermal isolation is important to maintaining the desired lower temperature in the freezer and the desired warmer temperature in the fresh food. Thermal isolation is also important to allow the fresh food evaporator to be defrosted using only the heat from the fresh food compartment. This heat is transferred using the fresh food evaporator fan. Finally, thermal isolation is important to avoid large quantities of water droplets forming on the fresh food side of the divider. This is less of a problem than with conventional single evaporator configurations, because of the increased fresh food airflow and better humidity control, but it is still a consideration.
A freezer fan 78 is positioned at one end of the evaporator housing 70. Fan 78 blows the refrigerated air from evaporator housing 70 into the freezer compartment 64 through opening 75. A fresh food compartment air fan 86 is positioned on an upper end of cavity 88 formed between the freezer compartment and fresh food compartment. The fan 86 blows refrigerated air into the fresh food compartment through opening 77. Each fan also draws air from within the freezer compartment and fresh food compartments, respectively, back into the evaporator housing 70 and cavity 88, over the respective portions of the evaporator. The air returns from the fresh food compartment to cavity 88 via an air return passage 90 positioned adjacent bottom wall 92. The air returns from the freezer compartment to housing 70 via an air return passage (not shown) formed near the bottom of evaporator housing 70. This arrangement, by isolating the air circulating in the fresh food compartment from the air circulated in the freezer compartment, includes among its advantages, higher humidity in the fresh food compartment, and prevention of odor transfer between compartments. The freezer compartment is maintained below freezing while the fresh food compartment is maintained above freezing by an appropriate division of the time the fans 78 and 86 are on to provide cooling to their associated compartments. A drain tube 94 is positioned adjacent a bottom wall 96 of the freezer compartment, and a separate drain tube 98 is positioned adjacent the bottom wall of the fresh food compartment.
In order to maintain the freezer compartment at sub-freezing temperatures, it is necessary that the evaporator operate at below freezing temperatures, with the result that moisture contained in the return air flowing through the evaporator chamber collects on the outer surfaces of the evaporator in the form of frost. Periodically this accumulated frost is removed from the evaporator surfaces by energizing a heater 100 positioned in radiant and convection or conduction heating relationship with the evaporator surfaces. This heater conveniently may be of the type such as disclosed in U.S. Pat. No. 5,067,322 assigned to General Electric Company, assignee of the present invention.
Referring again to evaporator 71, the serpentine tube configuration is formed and disposed in a fashion well known in the art. That is, the tube is bent in the form of serpentine to provide a plurality of elongated horizontal conduit passes disposed in a vertical spaced arrangement connected by return bends. The overall layout of the evaporator is a generally rectangular construction with the various elongated passes of the tube supported in spaced relationship of the evaporator. A frame can mount the evaporator in a generally vertical position within the evaporator compartment 70 and cavity 88. With this arrangement the air flows perpendicularly across the elongated sections of portions 72 and 74 of evaporator tubing. For example, the evaporator can include an elongated spine fin ribbon 102 wound or wrapped about the outer surface of a tube in an open spiral configuration as is well known in the art. Examples of such a spine fin evaporator is shown in U.S. Pat. Nos. 5,255,535; 5,241,840; and 5,241,838, all assigned to General Electric Company and hereby incorporated by reference.
Since the fresh food and freezer evaporator portions of the evaporator become flooded with refrigerant at the same time, if both compartments were cooled simultaneously, that is, if both evaporator fans were on at the same time, the evaporator temperature and pressure would be determined by freezer temperature. In this situation, there would not be an expected energy benefit. To achieve a more efficient system, the respective fresh food and freezer evaporator fans will be operated to cool the fresh food and freezer compartments sequentially. When the compartments are cooled sequentially, the evaporation temperature and pressure will increase during the fresh food portion of the cooling cycle. The cooling cycle will benefit from this increase in pressure and become more efficient. To fully capture this energy benefit, the fresh food portion of the evaporator preferably would be slightly larger than the freezer portion and the fresh food airflow would preferably be slightly greater than the freezer airflow. Practical cost and space considerations may prevail over what is optimum for energy. The fresh food heat load is removed at a faster rate than the freezer heat load because of the improved thermodynamic efficiency, so the portion of the cooling cycle spent cooling the fresh food is expected to be less than that spent cooling the freezer.
FIG. 10 illustrates a graph of design controls to utilize fresh food airflow for defrosting which saves energy and increases effective cooling capacity. This scheme also cools each compartment sequentially which improves the cooling cycle by allowing a warmer evaporation temperature during fresh food only cooling, reducing energy consumption. Fresh food defrost using a fan to circulate fresh food air over the fresh food evaporator has been common in commercial refrigeration for many years. It is also currently used on existing two evaporator designs for household refrigeration appliances. Originally, the fan was left running all the time. When the compressor shut off, the evaporator was defrosted using the heat from the fresh food compartment. A thermostat on the evaporator prevented the compressor from starting until the evaporator was warm enough to ensure all the frost had melted. With electronic controls for such systems, the fan does not need to run 100 percent of the time. In such systems, the evaporator temperature can be monitored, e.g., using a thermistor, and the fan can be shut off when the evaporator is sufficiently warm. This is implemented in the control scheme illustrated in FIG. 10.
FIG. 10 shows the operating states of the compressor and the fresh food and freezer fans for various temperature conditions of the fresh food and freezer compartments and the fresh food portion of the evaporator. For example, when the temperature in the freezer is “satisfied”, that is, the temperature is low enough to satisfy the freezer setpoint requirement, but the fresh food compartment is “too warm”, to satisfy the fresh food setpoint temperature, the fresh food fan is turned on, but the freezer fan remains off. The compressor will be off if the temperature of the fresh food portion of the evaporator is below a predetermined reference temperature high enough to assure frost is not present and low enough to provide cooling of the fresh food air, and will be turned on when that temperature is above the reference temperature. The fresh food fan remains on until the fresh food setpoint is satisfied and the evaporator temperature rises above the reference temperature. If the freezer is too warm, and the fresh food compartment is satisfied, the compressor is turned on and the freezer fan is turned on regardless of the evaporator temperature and the fresh food fan remains off. If both compartments are too warm, the compressor and the fresh food fan are turned on, but the freezer fan remains off until the fresh food compartment is satisfied, then the fresh food fan is turned off and the freezer fan is turned on. In the illustrative embodiment, the reference temperature is chosen to be 35° F.
In each of the foregoing examples, the system is not in the defrost operating mode. When the system calls for the defrost mode, signified by the setting of the defrost flag, the compressor and the freezer fan are turned off, and the fresh food fan is turned on, and remains on until the evaporator temperature rises above a predetermined temperature sufficient to assure the frost on the evaporator has been sufficiently removed, which in the illustrative embodiment is chosen to be 35° F. The initiation of a defrost mode may be determined by any of the many well known schemes for automatic defrosting, such as simply initiating defrost after a given amount of time has elapsed since the previous defrost cycle. Alternatively, a more sophisticated adaptive defrost cycle scheme may be implemented by monitoring compressor run time and possibly other system parameters, as is well known in the art.
The above-described system is more efficient at cooling than existing two evaporator systems, since there are not two separate evaporator components, and there is no need for valves to switch between the compartments, or extra tubing or joints for the refrigerant to pass through, since the evaporator is not located in the fresh food compartment, the space available in the fresh food compartment is maximized. The evaporator itself is about twice the size of an existing freezer evaporator. The evaporator system can also use a plate fin tubing assembly as well without departing from the scope of the invention.
The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations.

Claims

1. A cooling system for a refrigerator of the type having a fresh food compartment and a freezer compartment separated by a partition, comprising:

a compressor for compressing a refrigerant;

a condenser for the compressed refrigerant;

an evaporator comprising:

a freezer compartment evaporator portion and a fresh food compartment evaporator portion;

wherein said freezer compartment portion is located in the freezer compartment and the fresh food compartment evaporator portion extends into a cavity formed in the partition between said fresh food compartment and said fresh food compartment.

2. The cooling system of claim 1, wherein said evaporator comprises tubing in a serpentine configuration.

3. The cooling system of claim 1, further comprising an evaporator compartment formed within said freezer compartment and a fan for moving air into said freezer compartment from said evaporator compartment.

4. The cooling system of claim 1, further comprising a passage formed in the partition extending between said cavity and said fresh food compartment and a fan for moving air into said fresh food compartment from said cavity.

5. The cooling system of claim 2, wherein said tubing of said fresh food evaporator portion is folded to extend into said cavity.

6. The cooling system of claim 5, wherein said evaporator compartment further comprises a heater for heating said tubing of said evaporator.

7. The cooling system of claim 1, wherein said evaporator comprises spine fin tubing.

8. A refrigerator comprising:

a freezer compartment;

a fresh food compartment;

a compressor for compressing a refrigerant;

a condenser for condensing the compressed refrigerant;

an evaporator comprising a first portion for cooling the freezer compartment; and

a second portion for cooling the fresh food compartment, wherein said first and second portions are integral with each other.

9. The refrigerator of claim 8, wherein said evaporator comprises tubing in a serpentine configuration.

10. The refrigerator of claim 8, further comprising an evaporator compartment formed within said freezer compartment and a fan for moving air into said freezer compartment from said evaporator compartment.

11. The refrigerator of claim 8, further comprising a cavity formed in the partition between said freezer compartment and said fresh food compartment, and a fan for moving air into said fresh food compartment from said cavity, and wherein said second portion of said evaporator extends into said cavity 12. A method for evaporating refrigerant to cool freezer and fresh food compartments of a refrigerator, comprising:

providing a compressor for compressing the refrigerant:

providing a condenser for condensing the compressed refrigerant;

providing an evaporator which has a first portion for evaporating refrigerant to cool the freezer compartment and a second portion for evaporating refrigerant to cool the fresh food compartment, wherein said first portion and said second portion are integral to each other.