JPH02225953A - Freezing system with double vaporizer for domestic refrigerator - Google Patents

Abstract

PURPOSE: To raise the heat efficiency, by constituting the freezing system such that a phase separator connects the second evaporator to the first expansion valve in refrigerant flow relation, and that it gives intermediate cooling to the section between first compressor and the second compressor. CONSTITUTION: Vapor-phase refrigerant compressed with a compressor 15 is mixed with a vapor-phase refrigerant at saturation temperature from a vapor-phase separator 27, and further it is compressed with a compressor 17 and becomes a vapor-phase refrigerant at high temperature and high pressure, and then, it is condensed within a condenser 21. Next, the condensed vapor-phase refrigerant passes an expansion valve 23, and expands from high pressure to middle pressure lower than that within an evaporator 25. This refrigerant in liquid phase and vapor phase enters the phase separator 27, and the liquid-phase refrigerant is accumulated at the bottom of a container, and the vapor-phase refrigerant is accumulated at the upper part. Mixing the vapor-phase section of this refrigerant with the vapor-phase refrigerant having come out of the compressor 15 will cool the vapor-phase refrigerant having come out of the compressor 15, since the temperature of the vapor-phase refrigerant from the phase separator is about -3.9 deg.C, and the temperature of the gas refrigerant at the inlet of the compressor 17 becomes low. On the other hand, the liquid-phase section within two-phase mixed refrigerant from the evaporator 25 flows, passing through the expansion valve 11 from the phase separator 27, and the pressure of the refrigerant drops. This residual liquid- phase evaporates within the evaporator 13, and cools the evaporator 13.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to domestic refrigerators that operate on a vapor compression cycle, and more particularly to refrigerators that include a two-stage compressor.

Refrigerators currently produced operate on a simple vapor compression cycle. The cycle includes a compressor, condenser, expansion valve, evaporator, and two-phase refrigerant. In the prior art refrigeration cycle shown in FIG. 1, a capillary tube acts as an expansion valve. The capillary tube is placed in close proximity to the suction side line of the compressor in order to cool the capillary tube. The subcooling that occurs in the refrigerant in the capillary increases the cooling capacity per unit mass flow in the system, thereby increasing system efficiency, so that the temperature of the vapor phase refrigerant supplied to the compressor increases. The disadvantage of the increase is more than compensated for. The evaporator of Figure 1 operates at a temperature of about -10"F. Refrigerator air is routed across the evaporator and a portion of the airflow goes to the freezer compartment. The remainder is controlled to go to the fresh food refrigerator.Thus, the refrigeration cycle produces a refrigeration effect at a temperature suitable for the freezer but lower than that required by the fresh food refrigerator.Low temperature. A simple vapor compressor cycle uses more mechanical energy than a cycle that cools at two temperature levels because the mechanical energy required to cool it to a higher temperature is greater than that required to cool it to a higher temperature. do.

A well-known measure for reducing mechanical energy usage is the use of two separate refrigeration cycles, one operating at a low temperature for the freezer compartment and one operating at an intermediate temperature for the fresh food refrigerator compartment. It is. However, such a system is extremely expensive.

Another drawback that occurs during cooling for refrigeration operations in simple vapor compression cycles is the large temperature difference between the inlet and outlet of the compressor.

The gas phase refrigerant leaving the compressor has been heated. This represents a thermodynamic irreversibility, resulting in relatively low thermodynamic efficiency. Reducing the amount of superheat reduces mechanical energy usage and therefore increases efficiency.

One of the objects of the invention is to provide a refrigeration system for domestic refrigerators with improved thermodynamic efficiency.

A further object of the present invention is to provide a refrigeration system suitable for household refrigerators that lowers the temperature of the gas phase refrigerant at the compressor discharge port.

SUMMARY OF THE INVENTION In one aspect of the invention, a refrigeration system suitable for use in a domestic refrigerator having a freezer compartment and a fresh food storage compartment is provided. This refrigeration system includes a first expansion valve, a first evaporator for cooling the freezer compartment, a first compressor, a second compressor, a condenser, a second expansion valve, and a fresh food refrigerator compartment. and a second evaporator for cooling. All the above components are connected in series in a double order, refrigerant flow relationship. Additionally, - phase separators connect the second evaporator in refrigerant flow relationship to the first expansion valve and provide intercooling between the first compressor and the second compressor.

DETAILED DESCRIPTION OF THE INVENTION The gist of the invention is described in the claims, but the structure and method of carrying out the invention, as well as other objects and advantages of the invention, will be explained in the following description with reference to the accompanying drawings. may be best understood from.

The accompanying drawings, in particular FIG. 2 thereof, illustrate one embodiment of a dual evaporator two-stage system. This system includes a first expansion valve 11, a first evaporator 13, a first compressor 15, and a second compressor 1.
7, the condenser 21, the second expansion valve 23, and the second evaporator 2
5, and these components are connected in series in the above order by conduits 26 in a refrigerant flow relationship. Furthermore, a phase separator 27 is provided, which, as shown in cross-section in FIG.
is provided with a port 33 for taking in liquid and vapor phase refrigerants in its upper portion, and is separately provided with a first outlet 35 and a second outlet 37.

A screen 41 is installed in the upper part of this container 31 to remove any solid matter carried with the refrigerant when it enters through the inlet 33. The first outlet 35 is provided at the bottom of the container 31 and delivers the liquid phase refrigerant 39. The second outlet 37 is constituted by a conduit extending from the inside to the outside of the upper part of the container. This conduit 37 communicates with the upper part of the vessel, but is arranged so that liquid phase refrigerant entering the upper part of the vessel via the inlet 33 cannot enter through the open end of the conduit. The two-phase refrigerant coming out of the outlet of the second evaporator 25 is connected to the inlet 33 of the phase separator 27 . The phase separator 27 supplies liquid phase refrigerant to the first expansion valve 11 . The phase separator also provides a saturated vapor phase refrigerant which is combined with the vent refrigerant discharged from the first compressor 15 and connected together to the inlet of the second compressor 17 .

During operation, the temperature of the refrigerant in the first evaporator 13 is approximately −23.3° C. (approximately −10° C. below) for cooling the freezer compartment. Also, the temperature of the refrigerant in the second evaporator 25 is approximately -3.9C (approximately 25"F) for cooling the fresh food refrigerator compartment.

The first expansion valve is adjusted to provide a nearly non-drying vapor phase refrigerant flow. This adjustment can be achieved, for example, by observing a viewing glass provided in the line 26 between the first evaporator 13 and the first compressor 15. The gas phase refrigerant enters the first compressor 15 and is compressed. The gas phase refrigerant coming out of the first compressor is mixed with the gas phase refrigerant at the saturation temperature from the phase divider M device 27, and these two gas phase refrigerants are further transferred to the second compressor 17.
compressed by The high-temperature, high-pressure gas phase refrigerant discharged from the second compressor is condensed in the condenser 21 . Second expansion valve 23
is adjusted so that the liquid phase refrigerant exiting the condenser is somewhat properly cooled. This adjustment can be achieved, for example, by observing a viewing glass provided between the condenser 21 and the second expansion valve 23.

The liquid phase refrigerant condensed in the condenser 21 passes through the second expansion valve, and at this time, the high pressure in the condenser 21 is transferred to the second evaporator 25.
expands to a lower intermediate pressure within.

This expansion evaporates a portion of the liquid phase refrigerant and cools the remaining portion to the temperature of the second evaporator. The liquid phase and gas phase refrigerant enter the phase separator 27. Liquid phase refrigerant is stored in the lower portion of the vessel and vapor phase refrigerant is stored in the upper portion. A gas phase portion of the refrigerant is supplied from the phase separator to the gas phase refrigerant discharged from the first compressor 15 and mixed therewith. Since the gas phase refrigerant from the phase separator has a temperature of approximately -3°9C (approximately 25”F), the gas phase refrigerant exiting the first compressor is cooled (intercooled), which causes the gas phase refrigerant in the second compressor to cool. The temperature of the gaseous refrigerant at the inlet is lower than that without this intercooling.On the other hand, the liquid phase portion of the two-phase mixed refrigerant from the second evaporator 25 passes from the phase separator 27 to the first expansion valve 1. This remaining liquid phase refrigerant evaporates within the first evaporator 13, cooling the first evaporator to approximately -10"F. . The system is supplied with a sufficient amount of refrigerant to maintain a desired level of refrigerant in the phase separator.

The pressure ratio of the first and second compressors depends on the refrigerant used and the operating temperature of the evaporator. The population pressure of the first compressor 15 is determined by the pressure at which the refrigerant is in two-phase equilibrium at approximately -23.3°C (-10°C). The outlet pressure of the first compressor is determined by the saturation pressure of the refrigerant at approximately -3°9°C (25″F). It must be above ambient temperature. For example, if the condenser operates at I05"F, that determines the saturated refrigerant pressure. The volume displacement capacity of the compressor is determined by the cooling capacity required by the system at each of the two temperature levels, which determines the mass flow rate of refrigerant through the compressor.

A dual evaporator two-stage cycle requires less mechanical energy than a single evaporator single compressor cycle with the same cooling capacity.

In refrigerant compression, the vapor phase refrigerant leaving the evaporator at a higher temperature is compressed from an intermediate pressure, rather than the vapor phase refrigerant leaving the evaporator at a lower temperature being compressed from a lower pressure. This is more beneficial in terms of efficiency. or,
Adding the gas phase refrigerant taken out from the phase separator and cooled to the saturation temperature to the gas phase refrigerant coming out of the first compressor to cool it also contributes to efficiency improvement. Cooling the gas phase refrigerant entering the second compressor reduces the amount of mechanical energy required by the second compressor.

Another embodiment of the invention is shown in FIG. This system is
The first expansion valve 5, the first evaporator 53, and the first compressor 55
, which are connected in a refrigerant flow relationship by conduits 57 in series in the above order. The system further includes a second compressor 61, a condenser 63, a second expansion valve 65, and a second evaporator 67, which are connected in series to the line 6 in the above order.
9 in a refrigerant flow relationship. Furthermore, a phase separator 71 is provided, the cross-sectional view of which is shown in FIG. 75, and in its lower part, a second lower part 7 for introducing the gas phase refrigerant below the liquid level 8, and a first outlet 83 and a second outlet (pipe line) 85 are provided separately. ing. A screen 87 is installed in the upper part of this container to remove solids carried with the refrigerant when they enter from the first port 75. A first outlet 83 is provided at the bottom of the container and delivers liquid phase refrigerant. The second outlet 85 is constituted by a conduit extending from the inside to the outside of the upper part of the container. This conduit communicates with the upper part of the container,
The liquid phase refrigerant that entered from the first population 75 is the second outlet (pipe line) 8
It is arranged in such a way that it is impossible to enter inside 5. The two-phase refrigerant coming out of the outlet of the second evaporator 67 is transferred to a phase separator 71
It is in the first population of 75. The phase separator supplies liquid phase refrigerant to the first expansion valve 52 from a first outlet 83 of the phase separator. The gas phase refrigerant discharged from the first compressor 55 is introduced into the container 75 via the second lower person 7, where it is mixed with the liquid phase refrigerant. From the second outlet 85 of the container, gaseous refrigerant at the saturation temperature of the liquid refrigerant is sent to the second compressor 61 .

During operation, the temperature of the refrigerant in the first evaporator 53 is approximately -23.3°C (approximately -10"F) for cooling the freezer compartment. The temperature of the refrigerant in the second evaporator 67 is approximately -10"F for cooling the freezer compartment. It is approximately -3.9°C (approximately 25”F) for cooling food refrigerators. The first expansion valve 51 is adjusted to provide a nearly dry vapor phase refrigerant flow. This adjustment can be achieved, for example, by observing a viewing glass provided in the line 57 between the first evaporator 53 and the first compressor 55. Gas phase refrigerant is supplied to the first compressor 55
and is compressed. The gas phase refrigerant discharged from the first compressor is mixed with and directly contacts the liquid phase refrigerant in the phase separator 71, and the temperature of the gas phase refrigerant is lowered to the saturation temperature. Some of the liquid phase refrigerant is evaporated by the gas phase refrigerant entering from the second lower 7 of the phase separator. 20 The vapor phase refrigerant entering from the first compressor 55 is cooled to the saturated vapor phase temperature by the evaporation of the liquid phase refrigerant. The saturated gas phase refrigerant coming out of the upper part of the phase separator flows into the suction port of the second compressor 61. Second compressor 61
The high-temperature, high-pressure gas phase refrigerant discharged from the refrigerant is condensed in the condenser 63. The throttle of the second expansion valve 65 is adjusted so that the liquid phase refrigerant discharged from the condenser is cooled to some extent. This adjustment can be achieved, for example, by observing a viewing glass provided between the condenser 63 and the second expansion valve 65. The liquid phase refrigerant condensed in the condenser passes through the second expansion valve 65 and expands from the high pressure in the condenser to the lower intermediate pressure in the second evaporator 67 . Expansion of the liquid phase refrigerant evaporates a portion of the liquid and cools the remaining portion to the temperature of the second evaporator. The liquid phase and gas phase refrigerant enter the phase separator 71. The liquid phase refrigerant is accumulated in the lower part of the container, and the particulate refrigerant is accumulated in the upper part. The liquid phase refrigerant coming out of the phase separator flows through the first expansion valve 51, which expands the refrigerant and further reduces the pressure. This remaining liquid phase refrigerant evaporates in the first evaporator, cooling the first evaporator to about -23.3° C. (about 10 centimeters). The system is supplied with a sufficient amount of refrigerant to maintain a desired level of refrigerant in the phase separator.

A dual evaporator two-stage cycle requires 29% less mechanical energy compared to a single evaporator single compressor cycle with the same cooling capacity. Rather than compressing the vapor phase refrigerant from a lower pressure from the lower temperature evaporator 53, the higher temperature evaporator (second evaporator)
It is more advantageous in terms of efficiency to compress the gas phase refrigerant released from the tank from an intermediate pressure. Further, cooling the gas phase refrigerant discharged from the first compressor 55 to the saturation temperature before compressing it to the pressure on the high pressure side of the system in the second compressor 61 also contributes to efficiency improvement. The cycle shown in FIG. 2 is calculated to be about 2% more efficient than the cycle in FIG. In the configuration shown in FIG. 2, the gas-phase refrigerant inlet temperature of the second compressor 61 becomes higher, so a larger amount of compression work is required, but the cycle shown in FIG. The efficiency of the cycle is increased because a greater amount of intermediate pressure liquid phase refrigerant is available for expansion to. In the cycle of Figure 2, the inlet temperature of the second compressor is higher because not all of the gas phase refrigerant supplied to the second compressor is cooled to saturation temperature as in the cycle of Figure 4. Become.

When using refrigerant R-12, the relative sizes (volume displacements) of the first compressor and second compressor in the double evaporator two-stage cycle of FIGS. 2 and 4 have the same total refrigeration capacity. When the compressor size of a simple vapor compression cycle is 1, they are 0°27 and 0.45, respectively.

In the embodiment of FIGS. 2 and 4, the compressor may be a hermetically sealed motorized reciprocating compressor, a hermetically sealed motorized rotary compressor, or a hermetically sealed motorized positive displacement compressor. When using refrigerant R-12, the first compressor can be very small and operates at a pressure ratio of only 2. For this reason, for example, cheap diaphragm compressors can also be used. Furthermore, since it is more efficient to use a large electric motor than two small electric motors to obtain the same power, efficiency can be improved by driving both compressors with one electric motor.

Performance calculations for the cycles of FIGS. 1, 2, and 4 will be described below. All cycles use refrigerant R-1
2 will be used, and the total cooling capacity will be approximately 293.
It was assumed to be 1W (approximately 1000 Btu/h). Additionally, all cycles shall use a hermetically sealed motorized rotary compressor cooled with a refrigerant having compressor discharge pressure.

In the cycle shown in Figure 1, the evaporator outlet saturation temperature is set to about -23,
3℃ (approximately -10 below), pressure drop approximately 0.07 kgr/
c! (1 psi), the superheat at the outlet is 0°C (0 units), the compressor insulation effect is 0.61, the motor efficiency is 0, 8,
Additional superheating of the gas phase refrigerant during suction due to heat exchange from the compressor side is approximately 23.9°C (43″F).Capillary heat exchange to the suction line of the compressor causes the gas phase refrigerant to Refrigerant superheat will be approximately 98”F. The condenser has an inlet saturation temperature of approximately 54.4°C (130″F) and a pressure effect of approximately 0.
7 kgf'/c (10 psi), and the supercooling at the outlet is approximately 2.8°C (5 cylinders).

Calculations based on these variable values resulted in a motor discharge temperature of 220.6°C (429″F) and a refrigerant flow rate of 8.4k.
g/h (18,6 lbs/hr), compressor power 270
W, the performance efficiency was 1.09.

For the cycles of FIGS. 2 and 4, the first evaporator outlet saturation temperature is approximately -23.3°C (-10°C below) and the pressure drop is approximately 0.3°C. 07 kgf/cze (1 psi), the superheat at the outlet is 0°C (0”F), and the second evaporator has an outlet temperature of about -3,000 psi.
9°C (25”F) pressure drop to Okgf'/c (Ops
l). The adiabatic efficiency of the first and second compressors is set to 0.
7. The motor efficiency is set to 0.8, and the additional heating of the suction gas phase refrigerant by heat exchange from the compressor side of the first compressor is approximately 2.
8°C (5″F) and additional heating of the second compressor to approx.
℃ (10″F).

The condenser inlet saturation temperature is approximately 54.4°C (below 130°C), the pressure drop is approximately o, 7 kgf/cj (10psi)
, the subcooling at the outlet is approximately 2.8° C. (5″F). Approximately 293.1 W (approximately 1000 Btu/h) of the cooling capacity is bisected into this evaporator.

The result of calculating the cycle shown in Figure 2 from the above variable values is that the temperature of the gas phase refrigerant discharged from the second compressor is approximately 97.8"C (208"C).
F), the temperature of the gas phase refrigerant discharged from the first compressor is approximately 18,9℃ (6
6″F), the compressor flow rates of the first and second compressors are approximately 3.6 kg/h (8,01b sardine/hr) and approximately 1
1. 2kg/h (24,71b-/hr), the power consumption of the first and second compressors is 22゜4W and 16
4W, performance efficiency is 1.58.

As a result of calculating the cycle shown in Fig. 4 from the above variable values, the discharge gas phase refrigerant temperature of the first and second compressors is approximately 1
8.9℃ (66”F) and approximately 97.8”C (208”F)
), the flow rates of the first and second compressors are approximately 10. 7
g/h (23,6 lbm/hr), and about 3.
6kg/h (8,0lbm/hr), the power consumption of the first and second compressors is 22.2W and 156゜2W, respectively.
, the performance efficiency is 1.64.

The system of FIG. 4 can also be modified by changing the operation of the phase separator of FIG.

If the second person lower 7 is connected to the conduit of the second outlet 85,
Although the gas phase refrigerant exiting the outlet of the first compressor does not come into direct contact with the liquid phase refrigerant, cooling will still occur, if not to saturation temperature.

If the vapor phase refrigerant is in direct contact with the liquid phase refrigerant, the phase separator will act as a heat exchanger and provide intercooling between the two compressors, even though it is not cooled anywhere.

The above describes a refrigeration system with a double evaporator that has improved thermodynamic efficiency and is suitable for household refrigerators.

Although several preferred embodiments of the invention have been illustrated and described in detail, it will be understood by those skilled in the art that various changes in construction and detail may be made without departing from the spirit and scope of the invention. Good morning.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the above compression system according to the prior art used in domestic refrigerators. FIG. 2 is a diagram of one embodiment of a dual evaporator two-stage system according to the present invention. FIG. 3 is a cross-sectional view of the phase separator of FIG. 2. Figure 4 shows
FIG. 3 is a system diagram of another embodiment of a dual evaporator two-stage system according to the present invention. FIG. 5 is a cross-sectional view of the phase separator of FIG. 4. (Explanation of main symbols) 11...first expansion valve, 13...first evaporator, 15...
...first compressor, 17...second compressor, 21...condenser, 23...second expansion valve, 25...second evaporator,
27... Phase separator, 31... Container, 33... Inlet, 35... First outlet, 37... Second outlet, 51...
- First expansion valve, 53... First evaporator, 55... First compressor, 61... Second compressor, 63... Condenser, 6
5...Second expansion valve, δ7...Second evaporator, 71...
・Phase separator 7.73...container, 75...first population,
77...Second population, 83...First exit, 85...
Second outlet (pipeline).

Claims (1)

[Claims] 1. A refrigeration system used in a refrigerator having a freezing compartment and a fresh food refrigerating compartment, comprising a first expansion valve, a first evaporator for cooling the freezing compartment, and a first evaporator for cooling the freezing compartment. a compressor, a second compressor, a condenser, a second expansion valve, a second evaporator for cooling the fresh food refrigerator compartment, and a phase separator; All components up to the second evaporator are connected in series in refrigerant flow relationship in the order described above, and the phase separator connects the second evaporator to the first expansion valve in refrigerant flow relationship. A refrigeration system characterized in that the first compressor and the second compressor are connected to each other and provide intermediate cooling between the first compressor and the second compressor. 2. The refrigeration system of claim 1, wherein said phase separator includes means for receiving liquid and vapor phase refrigerant from said second evaporator and means for supplying liquid phase refrigerant to said first expansion valve. 3. The phase separator includes means for supplying saturated vapor phase refrigerant to the second compressor, whereby the second compressor receives vapor phase refrigerant from the first compressor and the phase separator. Refrigeration system according to item 2. 4. The refrigeration system according to claim 2, wherein said phase separator includes means for receiving vapor phase refrigerant from said first compressor and supplying vapor phase refrigerant at a saturated vapor phase temperature to said second compressor. 5. The phase separator is configured with a container that stores liquid phase refrigerant in its lower portion and vapor phase refrigerant in its upper portion, and the container supplies saturated gas phase refrigerant to the second compressor. 4. The refrigeration system of claim 3, further comprising means. 6. The phase separator is configured with a container that stores liquid phase refrigerant in its lower portion and vapor phase refrigerant in its upper portion, and the container is configured to transfer the gas phase refrigerant from the first compressor to the container. 5. The refrigeration system according to claim 4, further comprising means for introducing the refrigerant into a portion below the liquid level of the container, and means provided above the liquid level of the container for supplying the saturated vapor phase refrigerant to the second compressor. 7. A refrigeration system used in a refrigerator having a freezing compartment and a fresh food refrigerating compartment, comprising a first expansion valve, a first evaporator for cooling the freezing compartment, a first compressor, and a first compressor. A second compressor, a condenser, a second expansion valve, a second evaporator for cooling the fresh food refrigerator, and a phase separation device, from the first expansion valve to the second evaporator. All the components of are connected in series in refrigerant flow relationship in the above order, and the phase separator receives liquid and vapor phase refrigerants from the second evaporator and separates the liquid phase refrigerant from the second evaporator. It has means for supplying the saturated vapor phase refrigerant to the first expansion valve and the second compressor, whereby the vapor phase refrigerant from the first compressor and the vapor phase refrigerant from the vapor phase separation device are separated. is supplied to the second compressor. 8. A refrigeration system used in a refrigerator having a freezing compartment and a fresh food refrigerating compartment, comprising a first expansion valve, a first evaporator for cooling the freezing compartment, and a first compressor; a second compressor, a condenser, a second expansion valve, a second evaporator for cooling the fresh food refrigerator compartment, and a phase separation device, the first expansion valve and the first evaporator and the above-mentioned first compressor are, in series in the order of this description,
The second compressor, the condenser, the second expansion valve, and the second evaporator are connected in a refrigerant flow relationship in series in this order, The phase separation device receives liquid phase and gas phase refrigerant from the second evaporator, receives heated gas phase refrigerant from the first compressor, and supplies liquid phase refrigerant to the first expansion valve. A refrigeration system comprising means for supplying a gas phase refrigerant at a saturated gas phase temperature to the second compressor.