MXPA00002736A - Dual-service evaporator system for refrigerators - Google Patents

Abstract

The disclosed refrigeration appliance includes a fresh-food compartment (32) and a freezer compartment (34) with a plenum or duct (36) therebetween housing a single evaporator (30) and at least one fan (20) for establishing air flows through the plenum (36) in opposite directions, an air flow pattern through the plenum (36) and the fresh-food compartment (32) alternating with an air flow pattern through the plenum (36) and the freezer compartment (34). One-way air valves (22, 24, 26, 28) are located at opposite ends of the plenum (36), on opposing sides of the fan (20), and provide communication between the food compartments and the plenum. The one-way air valves allow an air flow to be established, selectively, either through the plenum (36) in the fresh-food compartment (32) or through the plenum (36) and the freezer compartment (34). Operating in a fresh-food compartment cooling mode, air from the fresh-food compartment (32) circulating over the evaporator coils (30) serves to defrost the evaporator coils.

Description

DOUBLE SERVICE EVAPORATOR SYSTEM FOR REFRIGERATORS BACKGROUND OF THE INVENTION Field of the Invention This invention involves an improved evaporator arrangement for a domestic refrigerator. Prior Art Figure 1 shows a conventional frost-free refrigerator using a single evaporator 10. A fan 12 moves the air through the evaporator 10 while the compressor (not shown) is operating, which cools the air. Most of the cooled air is inside the freezer compartment 14. A small portion of cold air is used to cool the fresh food compartment 16. An electric heater 18 is energized with the evaporator fan 12 and the compressor to defrost the coil of the evaporator. This arrangement is used virtually in all refrigerators in the United States with automatic defrosting. The main advantage of the arrangement shown in Figure 1 is the simplicity and low cost due to the use of only one evaporator and one fan. The single evaporator coil also reduces the space requirement, compared to two evaporator systems.

The main disadvantage with the conventional arrangement shown in Figure 1 is the high energy consumption associated with the use of a refrigerant at a single evaporation temperature to cool both compartments. The required refrigerant temperature is below the freezer temperature, while an efficient system could cool the fresh food compartment using evaporator temperatures that are -1.1 to -4.4 ° C higher than those required for the freezer. Because about half of the refrigeration load comes from the fresh food compartment, the amount of potential energy savings is 20% or more for a system that efficiently uses two evaporation temperatures. There are several different types of refrigerators that use two evaporators. The "brute force" solution is the use of two completely independent circuits with two compressors. This approach adds a great cost penalty to the additional components. In addition, the theoretical energy savings can be invalidated by the lower efficiency associated with the use of two smaller compressors instead of a large compressor, because the efficiency of the compressor generally worsens at small capacities. The Lorenz cycle is another approach that uses two evaporators.

It uses two evaporators connected in series essentially at the same evaporation pressure. Two evaporation temperatures are achieved using an azeotropic mixture of two or more refrigerants as the working fluid combined with the internal heat exchangers. The evaporation temperature of a mixture increases as the more volatile component evaporates and the liquid becomes rich in the less volatile component. An internal heat exchange is used so that two evaporation temperatures are created. Tests have shown that this arrangement offers energy savings of approximately 20% with hydrocarbons or HCFCs (hydrochlorofluorocarbons). A major problem is the instability to find a suitable non-flammable chloride free refrigerant mixture. Obtaining the appropriate refrigerant charge for each component in a mixture is also a problem that requires solution. Other refrigerators use a solenoid valve to exchange between two evaporators. A normal arrangement continuously cools the freezer evaporator and uses the solenoid valve to allow the refrigerant to be in the second evaporator only when required to cool the fresh food compartment. This arrangement is common in Asian refrigerators, and is used to achieve independent temperature control for each compartment. It usually does not provide significant energy savings because the coolant temperature is still below the freezer temperature when the fresh food compartment is cooled.

The random refrigeration system as described in the U.S. Patent. No. 5,406,805, is a recent improvement for the double evaporator configuration. This prior art system uses two forced convection evaporators, one for each compartment and each has its own dedicated fan. The control only returns one evaporator fan at a time. When the compressor is first, only the fresh food evaporator fan operates. Once the fresh food compartment is cooled, the controls turn off the fresh food fan and then turn on the freezer fan. Defrosting is achieved by operating only the fresh food fan and activating an optional solenoid valve to allow free circulation of refrigerant between the two evaporators. A thermosyphon effect allows the heat of the fresh food compartment to thaw the freezer evaporator without the need for an electric heater. This method of freezing requires that the fresh food evaporator be physically less than the freezer evaporator to allow it to work natural convection. Tests have shown energy savings of 10 to 20 percent compared to conventional single-evaporator systems. Although the random system is a major improvement compared to conventional single-evaporator systems, two evaporators and two evaporator fans are still required. SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide a refrigerator that operates more efficiently than conventional refrigerators that are currently available. Another objective of the present invention is to provide the benefits provided by the random refrigeration system, but with only one evaporator and one evaporator fan in order to reduce the cost of the system and improve its efficiency. In order to meet the above objectives, the present invention provides an electric refrigerator having a fresh food compartment and a separate freezer compartment. The first and second walls separate the freezing compartment from the fresh food compartment and define therein a impeller housing the reversible ventilation means for alternating circulation of a cold air flow through the fresh food compartment and then through the freezing compartment. The first wall separates the impeller from the freezer compartment while the second wall serves to separate the impeller from the fresh food compartment. The electric cooling also includes a single compressor, a condenser and a single evaporator located in the impeller. The refrigerant circuit is in the form of a plurality of tubes that are interconnected to provide a flow of refrigerant, in succession, through the compressor, evaporator, condenser and the back of the compressor. The reversible venting means are located within the impeller to produce flow flow through the freezing compartment in a first direction and, alternatively, to produce a flow of cool air through the fresh food compartment in a second direction, opposite to the first address. At least a first pair of air valves are located on the first and second walls on opposite sides of the reversible venting means, one of which opens in response to the air flow in the first direction and closes in response to the air flow produced by the fan in the second direction. The other of the first pair of air valves opens in response to the flow of air in the second direction and closes in response to the air flow in the first direction. In a preferred embodiment, the electric cooler further includes a second pair of air valves located at opposite ends of the impeller with reversible venting means therebetween. In this modality, both air valves in the first wall open in response to the air flow in the first direction and close in response to the air flow in the second direction. Likewise, the air valves in the second wall could open in response to the air flow in the second direction and close in response to the air flow in the first direction. In the preferred embodiment, the reversible ventilation means consist of a single fan that is driven to alternate rotation in the clockwise direction or in the counterclockwise direction by a reversible motor. In a preferred embodiment, the air valves in the first and second walls are one-way vane valves. Accordingly, the present invention provides the following advantages: 1. A single evaporator provides efficient and independent refrigeration for both freezing and fresh food compartments. 2. A simple combination of a reversible fan and control blades provided to direct cooling to the fresh food compartment or to the freezer compartment. 3. The hot liquid refrigerant, instead of a separate heat source, is used to heat the blade valve contacts to prevent blade valves from closing to freezing point; and 4. The air in the fresh food compartment is used to defrost the same evaporator coil that serves the freezer compartment. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: Figure 1 is a schematic view of a prior art refrigerator having a freezer compartment and a fresh food compartment; Figure 2 is a schematic illustration of a preferred embodiment of the present invention operating in a cooling mode for the freezing compartment. Figure 3 is a schematic illustration of the preferred embodiment of Figure 2 operating in Figure 1 but operating in a combined defrosting mode and, simultaneously, in a cooling mode of the fresh food compartment I and a freezing mode for the freezing compartment; and Figure 4 is a schematic view of a complete refrigeration circuit, including the evaporator shown in Figures 2 and 3. DESCRIPTION OF PREFERRED MODALITIES Figures 2 and 3 illustrate a preferred embodiment of the present invention employing a reversible fan 20 and four vane or air valves 22, 24, 26 and 28 which are controlled to allow a single evaporator 30 to alternately cool a fresh food compartment 32 and a freezing compartment 34. The vane valves 22-28 serve as valves single direction or control, which allow the flow of air only in one direction. Consequently, when the fan 20 blows to the left as in the drawings, the air valves 26 and 28 of the freezing compartment are opened by the air flow to allow the circulation of cold air through the freezing compartment, i.e. , the air cooled by the passage on the evaporation coil 30. With the air flow to the left as shown in the drawing, ie the cooling mode for freezing, the blades of the air valves 22 and 24 are closed forcedly When the fan 20 is reversed to establish an air flow through the impeller 36 to the left in the drawing, each of the air valves is reversed to set the cooling mode of the fresh food compartment in combination with a cooling mode. defrosting the freezing compartment as shown in Figure 3. Therefore, in Figure 3, an air flow is established by the fan 20 through the impeller 28 and through the fresh food compartment 32. In this mode, the blades of the air valves 22 and 24 are forced open by the air flow while the blades of the air valves 26 and 28 are closed. In the configuration of Figure 3, the air of the fresh food compartment, it moves on the evaporator coil to melt any ice accumulation from it, thus thawing the evaporator coil. Molten ice also provides useful cooling for the fresh food compartment 32. Therefore, the energy requirement for defrosting is almost zero, representing a 5-10% saving in total energy compared to a conventional refrigerator.

The vanes of air valves 22, 24, 26 and 28 must be made of a material of very light weight because the air pressure of the fan may be able to open these vanes, still rigid enough to avoid the return flow. A suitable material to be used in the manufacture of the blades is a rigid thin sheet of polystyrene foam with a smooth covering on both surfaces. To overcome the potential for icing on the surface of the vanes of the air valves, the contacts for the vanes in their closed position can be ducts, exemplified by 38 and 39 in Figures 2 and 3, which receive the coolant to heat the refrigerant circuit (see Figure 4). The use of liquid refrigerant to heat blade surfaces saves energy in two ways, compared to the more conventional use of electric heaters for similar purposes in refrigerators. First, the refrigerant does not require additional electrical power to provide heat. Second, the cooled liquid gives an additional cooling effect in the evaporator that accurately deflects the heat provided. This second advantage means that no additional compressor energy is required to remove the heat beyond which it provides the liquid refrigerant. These combined effects do not imply energy penalty for heating, that is, the energy penalty for heating using the coolant is essentially zero.

While the mode of Figure 2 and 3 is shown to have four air valves, two of these air valves could be eliminated if the resultant air leak between the freezer compartment and the fresh food compartment is acceptable. The logical configuration for the operation with the two air valves could have an air valve to freeze and an air valve for fresh food located at the opposite ends of the duct or impeller 38. Two of said air valves are the minimum necessary to provide adequate control. The reversible fan 20 in Figures 2 and 3 is suitably a propeller fan with a motor that can reverse its direction of rotation. In an alternative mode, two blades could be used in series and placed to blow in opposite directions having only one fan in operation at any time. This alternative embodiment has the advantage of avoiding the need for a reversible fan but suffers from the disadvantage of requiring a second fan. A problem with this alternative mode is that the air also passes through the fan that is not in operation, thus restricting the flow of air and creating an additional pressure drop. Figure 4 shows the overall cooling circuit including the evaporator 30 shown in Figures 2 and 3. As shown in Figure 4, the vaporized refrigerant leaving the evaporator 30 is routed, in succession, through a compressor 40, a condenser 42, the hot liquid refrigerant lines 38, 39, the liquid suction heat exchange 31, the lid tube 32 and then return to the evaporator 30. A liquid suction heat exchanger 32 is downstream of the hot lines. A portion of the liquid suction exchanger may also be upstream of the hot liquid lines, as shown in Figure 4, along the surface in the air valves that remain sufficiently hot to allow free operation of the air valves. A liquid suction heat exchanger for the air valves, also called an in-line suction heat exchanger, is normally included in domestic refrigerators and uses the hot condensing liquid to heat the suction gas (gaseous refrigerant) on the way to the compressor to improve the performance of the cycle and reduce the undesirable heat gain in the suction gas from the environment. The different control modes for the operation of the cooling system are described in Figure 4 which is shown in the following table.

Table: Summary of Control Modes In operation, when the temperature inside the fresh food compartment 32 rises above the predetermined temperature, a signal is provided by a thermosensor or thermostat indicating that cooling is required. In response to said signal, the fan 20 is operated in the cooling mode in the fresh food compartment as described in Figure 3. Due to air circulation from the fresh food compartment over the evaporator coil 30, the The refrigerant is evaporated and the evaporator 30 exits in a gaseous state. After passing through the compressor 40, the refrigerant is at a high pressure and high temperature, the refrigerant is at a high pressure and high temperature (approximately 60-82.2 for the refrigerant R12). As the refrigerant passes through the condenser 42, the heat is removed by natural convection and / or forced convection if a fan is present. The refrigerant then leaves the condenser at approximately the same pressure as it is present at the condenser inlet, however with the coolant fully liquid, and now at a temperature of approximately 32.2 ° C (or approximately -12.2 ° C above ambient) . Therefore, the present invention combines the energy efficiency of double evaporator systems with simplicity, low cost and a compaction that approaches the systems of a single evaporator. An additional advantage, over the random system, is that thawing with the present invention could work in the same way with the freezer located under the fresh food compartment. The invention can be modalized in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments, therefore, can be considered in all respects as illustrative and not restrictive, the scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes that occur within the meaning and equivalence scale of the claims, therefore, it is intended that they be included in it.

Claims (9)

1. CLAIMS 1. An electric refrigeration appliance that includes: a compartment for fresh food; a freezing compartment; first and second walls separating the freezing compartment from the fresh food compartment and defining a plenum between them, the first wall separating the freezer compartment buffer and the second wall separating the impeller from the fresh food compartment; a single evaporator located in the impeller; a capacitor; a single compressor; a refrigerant circuit comprising a plurality of conduits for supplying a flow of refrigerant in succession, through said compressor, evaporator, condenser and the rear part of the compressor; the means of reversible ventilation, to produce an air flow in a first direction through the impeller and over the evaporator and in a second direction through the impeller and over the evaporator; a first air valve located in the first wall, at one end of the impeller, the first air valve opening in response to the flow of air in the first flow direction to establish a flow of air flow through the freezing compartment and closing in response to the flow of air in the second direction of flow; a second air valve located in the second wall at one end of the opposite impeller at one end, with reversible venting means being located between the first and second air valves, said second air valve opening in response to the air flow in the second flow direction to establish a flow of air flow through the fresh food compartment and closing in response to the flow of air in the first direction of flow; and control means for reversing the direction of air flow between the first and second directions. An electric refrigeration appliance according to claim 1, further comprising: a third valve located in the first wall at the opposite end of the impeller with reversible venting means being located between the first and third valves, the third valve of air opens in response to the flow of air in the first flow direction and closing in response to air flow in the second flow direction; and a fourth air valve located in the second wall at one end, with the reversible venting means located between the second and fourth air valves, the fourth air valve opens in response to the flow of air in the second flow direction and closes in responses to the flow of air in the first flow direction 3. An electric refrigeration appliance according to claim 1, wherein the first and second air valves are one-way vane valves. 4. An electric refrigeration appliance according to claim 2, wherein the first and second air valves are one-way fan valves. An electric refrigeration appliance according to claim 1, wherein the reversible ventilation means consist of a single fan and a reversible motor to reversibly drive the single fan. 6. An electric refrigeration appliance according to claim 2, wherein the reversible vent means consist of a single fan and a reversible motor to reversibly drive the single fan. 7. An electric refrigeration appliance according to claim 3, wherein the reversible vent means consist of a single fan and a reversible motor to reversibly drive the single fan. 8. An electric refrigeration appliance according to claim 4, wherein the reversible vent means consist of a single fan and a reversible motor to reversibly drive the single fan. 9. A refrigeration method comprising: providing a refrigerator comprising a fresh food compartment and a freezing compartment, with the first and second walls separating the freezing compartment from the fresh food compartment and defining an impeller therebetween, the first wall separating the impeller from the freezer compartment and the second wall separating the impeller from the fresh food compartment; a first air valve located in the first wall at one end of the impeller and opening in response to the flow of air in the first flow direction; and a second air valve located in the second wall at one end of the opposite impeller at one end, with the fan being located between the first and second air valves; and a single evaporator located in the impeller; a capacitor; and a single compressor; circulate a flow of the refrigerant, in succession, through the compressor, evaporator, condenser and the back of the compressor; alternatively produce an air flow in a first direction through the impeller and over the evaporator and through the first air valve to circulate the air flow through the freezing compartment and produce a flow of air in a second direction through of the impeller and on the evaporator, to open the second air valve, to close the first air valve and thus circulate the air flow through the fresh food compartment; and selectively shutting down the compressor with the air flow in the first flow direction to thaw the freezing compartment.