BACKGROUND OF THE INVENTION The present invention generally relates to domestic refrigerators and freezers. More particularly, the present invention relates to a system and method for utilizing cool outdoor ambient temperature levels to reduce the energy required to operate a domestic refrigerator or freezer system. Virtually every home and apartment in this country has at least one refrigerator for storing perishable food products. Additionally, many households also have a freezer for storing food products over extended periods of time. As a consequence of such widespread usage, these domestic appliances consume a substantial part of the electrical energy which is generated by the nation's utility companies. In this regard, it should be noted that refrigerators are considered to be a relatively inefficient appliance. Indeed, it has recently been reported that aside from electric heaters, refrigerators rank as the next most inefficient appliances in the home. Since even the newest refrigerators consume approximately 700kwh of electricity per year, it should be understood that a substantial need still exists to increase the energy efficiency of domestic refrigeration appliances.

Accordingly, it is a principal objective of the present invention to provide a system and method which reduces the energy required to operate domestic refrigerator and freezer systems. It is another objective of the present invention to provide an energy efficient domestic refrigeration system which minimizes the heat generated inside a home when the outdoor ambient temperature exceeds a desired indoor temperature. It is a further objective of the present invention to provide a domestic refrigeration system which may be applied to retrofit existing domestic refrigeration

units or applied at the factory to new domestic refrigeration units.

It is an additional objective of the present invention to provide a domestic refrigeration system which reduces the quantity of refrigerant needed in the system.

SUMMARY OF THE INVENTION To achieve the foregoing objectives, the present invention provides an energy transfer system for a household refrigeration appliance. The energy transfer system includes a compartment for enclosing the condenser which is associated with the refrigerator, and a set of conduits for enabling the transfer of outside air into, through and out of the compartment. The system also includes a movable barrier for selectively controlling the transfer of air through the compartment. In one form of the present invention, the system also includes a thermostatically actuated fan for forcing outside air into, through and out of the compartment in response to a predetermined temperature.

The set of conduits preferably includes a first conduit for enabling the transfer of outside air to the compartment, and a second conduit for enabling the transfer of air from the compartment to the outside environment. Each of these conduits are disposed such that they extend through an external wall of said household. To facilitate the convection flow of air, the outlet of one conduit is connected to the compartment at a location which is lower than an inlet connection of the other conduit. Additional features and advantages of the present invention will become more fully apparent from a reading of the detailed description of the preferred embodiment and the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a household refrigeration appliance in accordance with the present

invention.

Figure 2 is a side elevation view of the refrigerator shown in Figure 1.

Figure 3 is a schematic representation of a refrigeration system.

Figure 4 is a graph of the vapor-compression refrigeration cycle for the refrigeration system of Figure 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figure 1, a perspective view of a household refrigeration appliance 10 in accordance with the present invention is shown. More specifically, the household refrigeration appliance depicted in Figure 1 is a domestic refrigerator which has been retro-fitted with the energy transfer system 12 in accordance with the present invention. However, it should be understood that the principles of the present inventions are equally applicable to a domestic refrigerator which has been constructed at the originating factory to include a built- in energy transfer system. Additionally, it should be appreciated that the present invention is directed at household refrigeration appliances, such as self-contained refrigerators and freezers, that are specifically adapted for use in a home environment. In this regard, it should be understood that a completely different set of constraints and design criteria may be employed with commercial refrigeration equipment, which have a compressor and refrigerator cabinet in separate locations. As shown in Figure 1, the refrigerator 10 generally includes at least one door 14 across it's front and a serpentine tube condenser 16 mounted across it's back. As well known in the field, the condenser 16 is connected to the discharge end of a pump to compress a refrigerant fluid, such as freon, from a gaseous phase to a liquid phase. This process creates heat which must be removed in order for the refrigeration cycle to work. In

this regard, Figure 3 shows a schematic diagram of a conventional refrigeration cycle, with the pump indicated by reference numeral 18. An expansion valve 20 is used to permit the compressed refrigerant to expand in an evaporator coil 22, which is disposed within the interior of the refrigerator 10. This process of expansion operates to remove heat from the interior of the refrigerator 10.

With this household refrigerator arrangement, the heat produced at the condenser 16 is simply released into the area of the home which surrounds the refrigerator. However, in accordance with the present invention, a compartment 24 is used to enclose the condenser 16. As shown in Figure 1, the compartment 24 may be comprised of a five-sided molded fiberglass shell which is mounted to the exterior side of the refrigerator 10 where the condenser 16 is located. In this.regard, the compartment 24 includes a flange 26 which extends around its periphery in order to able the compartment to be secured to the refrigerator 10 over the condenser 16, such as with a plurality of spaced screws. However, it should be understood that the compartment may be comprised of other suitable materials and may take other suitable shapes in the appropriate application. For example, with a factory built-in energy transfer system, the compartment 24 may be formed integrally with a side of the refrigerator 10, such that the consumer need not discern that the compartment is included as part of the refrigerator body. Additionally, the compartment 24 may be constructed such that it includes an insulative layer in order to more fully control the transfer of heat from the condenser 16.

The energy transfer system 12 also includes one or more passageways for enabling the transfer of heat out of the compartment 24 and for selectively utilizing outside air in this process. Thus, for example, as shown in Figures 1 and 2, the energy transfer system 12 includes a first conduit 28 which enables cool air from outside of the home to enter the compartment 24, and a second conduit 30

which enables air from inside the compartment to be released outside of the home. In this regard, both of these figures show an exterior wall 32 of the household wall, and the conduits 28 and 30 are constructed such that they are able to extend through this exterior wall. The conduits 28 and 30 may be made of any suitable material which is appropriate for this purpose (e.g., sheet metal or flexible insulated duct) , and the conduits may be connected to the compartment in a variety of ways. It should also be noted that the first conduit 28 is connected to the compartment 24 at a location which is lower than that where the second conduit 30 is connected to the compartment. This arrangement is used to facilitate outside air from through the first conduit 28 into the compartment, through the compartment and out of the second conduit 30 by heat convention. While the conduits 28-30 are shown to be relatively straight pipes or tubes, it should be understood that other suitable shapes may be employed, depending upon such considerations as the available space and the distance between the refrigerator 10 and the exterior wall 32.

Figures 1 and 2 also show the provision of a fan 34, which may be used to force the flow of outside air into, through and out of the compartment 24. While the fan 34 is shown to be connected to the compartment 24 in a way which is separate than the connection of the conduits 28-30 to the compartment, it is preferred that the fan be connected in-line with the first conduit 28, either within the conduit or adjacent to its outlet into the compartment. Additionally, it is preferred that the fan 34 be a thermostatically actuated fan, so that the its use may be carefully controlled to achieve the most energy efficient benefit.

Additionally, as shown in Figures 1 and 2 , the energy transfer system 12 also includes a movable barrier or wall in one or both of the conduits 28-30 to control the flow of air through the compartment 24. In one form of the

present invention, this movable barrier is comprised of a butterfly valve 36 which may be used to prevent or enable the flow of outside air into the compartment via a butterfly valve disposed in one or both of the conduits 28- 30. For example, in the case of butterfly valve 36 disposed in the second conduit 30, the flow of outside air through the first conduit 28 could provide sufficient force to open the butterfly valve, and thereby permit the escape of air from the compartment 24 through the second conduit. From the above, it should be understood that the energy transfer system 12 conveys energy in the form of cool outside air to the condenser 16, in order to reduce the energy consumption of the refrigeration process. In other words, the present invention transfers available energy from the environment to the refrigeration cycle components, instead of having to transfer some of these refrigeration cycle components outside to the environmental energy source. The introduction of available energy to the refrigeration cycle reduces the energy required from the cycle, and consequently increases the overall energy efficiency of the refrigerator 10. This increase in energy efficiency would also enable the use of smaller, more efficient refrigeration components and reduce the amount of refrigerant required for a new refrigerator unit. The following analysis may be used to demonstrate the energy efficiency improvement by examining the increase in the refrigerator enthalpy "h". This analysis is set forth below in connection with the reference points shown in Figures 3 and 4. Assume 1: In the evaporator the heat absorbed per unit mass = the change in enthalpy of the refrigerant. Assume 2: At point 7 the refrigerator is a saturated liquid. Assume 3: At point 8 the refrigerator is a saturated gas. Assume 4: The refrigerant is freon - 12.

Assume 5: Typically the temperature around the expansion valve is 40°C and the temperature existing at the evaporator is -20°C. Following all the assumptions the enthalpys are below: h ₅ at 40°C = 74.527 KJ/KG h ₅ at 10°C = 45.337 KJ/KG h ₈ at -20°C = 184.619 KJ/KG P ₈ is 150 KPa h ₈ - h ₅ (40°C) = 110.092 = X, h ₈ - h ₅ (10°C) = 139.282 = X ₂

Increase in heat per unit mass absorbed at a percentage Y = ∑ ₂ — ₁ ^{= 20} - ⁹⁶ % increase.

^X 2 In other words, assuming that the outside air temperature is low enough such that the temperature at point 8 can be brought down to 10°C from' a level of 40°C, then a 20.96% increase in heat per unit mass absorbed may be achieved.

Thus, in accordance with the present invention, the fan 34 may be actuated when the outside air temperature drops to a predetermined threshold level (e.g., 37°C) , as the energy efficiency achieved will be greater than the energy consumed by the fan. Alternatively, it should be appreciated that the refrigerator 10 may already include a fan which may be used to divert some air flow into the compartment 24 from the outside. The energy transfer system 12 may also include a thermostatically actuated valve, such as the valve which would enable ambient air from inside the household (e.g., 20°C) to enter the compartment 24 when the outside air temperature is above a particular threshold level (e.g., 37°C) In this way, the compartment 24 will always be provided with a sufficient supply of air flow to cool the condenser 16. The present invention has been described in an illustrative manner. In this regard, it is evident that those skilled in the art once given the benefit of the foregoing disclosure, may now make modifications to the specific embodiments described herein without departing from the spirit of the present

invention. Such modifications are to be considered within the scope of the present invention which is limited solely by the scope and spirit of the appended claims.