JPH06317358A - Refrigerator - Google Patents

Abstract

PURPOSE:To improve refrigerating capacity at the time of a low temperature by providing an auxiliary heat exchanger for heat exchanging refrigerant between a first pressure reducing unit and a second pressure reducing unit with refrigerant of an outlet of an evaporator. CONSTITUTION:An auxiliary heat exchanger 7 for heat exchanging refrigerant between a first pressure reducing unit (capillary tube) 3 and a second pressure reducing unit (motor-driven expansion valve) 4 with refrigerant of an outlet of an evaporator 5 thereby to cool the refrigerant between the unit 3 and the unit 4 with the refrigerant of the outlet of the evaporator 5, and an enthalpy is reduced. Accordingly, dryness of the refrigerant fed to the evaporator 5 is reduced. Further, since the refrigerant between the unit 3 and the unit 4 is used to cool the refrigerant of the outlet of the evaporator 5, mean dryness of the refrigerant of the outlet of the evaporator 5 having large dryness is reduced, and an evaporating pressure for obtaining the same temperature is raised. Thus, refrigerating capacity at the time of a low temperature is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system using a non-azeotropic mixed refrigerant.

[0002]

2. Description of the Related Art Refrigerants, such as R22 and R502, used in vapor compression refrigeration systems are regulated because they contain chlorine molecules and, if released into the atmosphere, destroy ozone in the stratosphere. It's starting. As a refrigerant that does not destroy the ozone layer, for example, a refrigerant that does not contain chlorine molecules such as R32 and R134a is conceivable. As described in Japanese Patent Publication No. 1-200153,
There is known a method of obtaining characteristics suitable for a refrigerating apparatus in which a plurality of high boiling point refrigerants and low boiling point refrigerants are mixed and used.

[0003]

When a non-azeotropic mixed refrigerant in which a plurality of refrigerants are mixed is used as in the above-mentioned conventional example, there is a problem that the capacity is remarkably lowered when the evaporation temperature is lowered. That is, the non-azeotropic mixed refrigerant has a characteristic that the temperature changes at the time of phase change and, when viewed at the same temperature, the evaporation pressure decreases as the dryness of the refrigerant increases. For this reason, when the evaporation temperature decreases, the difference in the condensation temperature increases, and in a refrigerating apparatus using a pressure reducer, the dryness of the evaporator inlet increases, and the pressure of the evaporator decreases. As a result, there is a problem that the specific volume at the inlet of the compressor increases and the refrigerating capacity decreases.

Further, R32 and R are used as non-azeotropic mixed refrigerants.
When 134a is used, R which is conventionally used
22 and R502, there is a problem in that the ability of the refrigerant at a low temperature also deteriorates in terms of physical properties.

A first object of the present invention is to reduce the dryness of the evaporator and increase the evaporation pressure even if the evaporation temperature decreases.
An object of the present invention is to provide a refrigerating device in which a reduction in refrigerating capacity is small.

A second object of the present invention is to increase the refrigerating capacity by allowing the high-boiling-point refrigerant to stay and increasing the refrigerant composition circulating in the refrigerating apparatus to contain the low-boiling-point refrigerant component when the evaporation temperature decreases. To provide such a refrigerating device.

[0007]

In order to achieve the above first object, a compressor, a condenser, a pressure reducer and an evaporator are connected,
In a refrigeration system in which a non-azeotropic mixed refrigerant is sealed, a first pressure reducer and a second pressure reducer are provided as pressure reducers, a refrigerant between the first pressure reducer and the second pressure reducer, and an evaporator. An auxiliary heat exchanger for exchanging heat with the refrigerant at the outlet is provided.

Further, the above second object is achieved by providing a liquid receiver at the outlet of the evaporator.

[0009]

In the refrigeration system, the first pressure reducer and the second pressure reducer are provided as pressure reducers to assist the heat exchange between the refrigerant between the first pressure reducer and the second pressure reducer and the refrigerant at the outlet of the evaporator. By providing the heat exchanger, the refrigerant between the first pressure reducer and the second pressure reducer is cooled by the refrigerant at the outlet of the evaporator, and the enthalpy is lowered. Therefore, the dryness of the refrigerant entering the evaporator is reduced. Furthermore, since the refrigerant with a high dryness at the evaporator outlet uses the refrigerant between the first pressure reducer and the second pressure reducer to cool the refrigerant at the evaporator outlet, the average dryness of the evaporator decreases, The evaporation pressure for obtaining the same temperature is higher.

Further, by providing the liquid receiver at the outlet of the evaporator, the composition of the high boiling point refrigerant of the liquid refrigerant flowing into the liquid receiver increases as the evaporation temperature decreases, and the refrigerant circulating in the refrigerating apparatus. The low boiling point component of the composition is increased and the refrigeration capacity is increased.

[0011]

EXAMPLES The present invention will be described below with reference to examples.

FIG. 1 is a block diagram of a refrigerating apparatus according to an embodiment of the present invention. FIG. 2 shows the operating state of the refrigerating apparatus of the present invention on the Mollier diagram, in which the solid line shows the present embodiment and the broken line shows the conventional example.

In FIG. 1, 1 is a compressor for compressing a refrigerant, 2 is a condenser, 3 is a capillary tube as a first pressure reducer, 4 is an electric expansion valve as a second pressure reducer, and 5 is an evaporator. , 6 is a liquid receiver, 7 is an auxiliary heat exchanger, an intermediate pressure pipe 8 and a low pressure pipe 9 between the capillary tube 3 and the electric expansion valve 4.
Is provided so that heat can be exchanged. A fine oil return hole is provided in the lower portion of the low-pressure pipe in the liquid receiver 6. The electric expansion valve 4 stores in the controller (not shown) the difference between the evaporator refrigerant temperature detected by the evaporator temperature detector 10 and the compressor suction refrigerant temperature detected by the compressor suction refrigerant temperature detector 11. The opening is controlled so as to reach the set value that is set. When the temperature detected by the compressor outlet refrigerant temperature detector 12 becomes equal to or higher than a set value, the electric expansion valve 3 is controlled so as to reach the set value. The refrigerant is R134a as a high-boiling-point refrigerant and R32 as a low-boiling-point refrigerant is sealed in a ratio of 7/3.

The operation of the refrigerating apparatus configured as described above will be described with reference to FIGS. The refrigerant having the pressure P1 and the enthalpy h1 in the compressor 1 radiates heat in the condenser 2 and the pressure P
1, becomes the liquid refrigerant of enthalpy h2 and is sent to the pressure reducer. Pressure P due to isenthalpic change in capillary tube 3
After the pressure is reduced to 2, it is cooled by the auxiliary heat exchanger 7 and becomes enthalpy h3. Further, the pressure is reduced to P3 by the electric expansion valve 4 and enters the evaporator 5. After absorbing heat from the surroundings in the evaporator 5 and becoming enthalpy h4, it enters the liquid receiver 6 and a part of the liquid refrigerant remains in the liquid receiver. The gas refrigerant flows into the low-pressure pipe 9 at the upper part of the receiver, and a part of the liquid refrigerant flows out from the fine holes for oil return provided in the low-pressure pipe 9 below the receiver. After that, the refrigerant enters the auxiliary heat exchanger 7, absorbs heat from the intermediate pressure pipe 8, becomes enthalpy h5, and returns to the compressor 1. Therefore, the enthalpy of the refrigerant entering the evaporator 5 is reduced, and the dryness can be reduced. Further, in the range where the enthalpy is large and the degree of dryness is large, the degree of dryness of the evaporator is reduced and the evaporation pressure can be increased because it is used for heat exchange in the auxiliary heat exchanger 7. When compared with the conventional example shown by the broken line in FIG. 2, the evaporation temperature is −40 ° C. and the evaporation pressure is about 1
Can be increased by 0%. Furthermore, the higher evaporation pressure reduces the work of compression and improves the efficiency of the refrigeration system.

Further, the composition of the liquid refrigerant entering the liquid receiver 6 is higher in composition of R134a, which is a high boiling point refrigerant, as the evaporation temperature becomes lower, due to the characteristics of the non-azeotropic mixed refrigerant, and at -40 ° C.
Under the conditions of the present embodiment, it is about 83%, and the composition of R32, which is a low boiling point refrigerant circulating in the refrigeration system, becomes large. For example, the amount of liquid refrigerant in the liquid receiver is 3 times the amount of refrigerant enclosed in the refrigeration system.
In comparison, the refrigerant composition of R134a circulating in the refrigeration system is about 36%, and the refrigerating capacity is increased by 7%.

Further, when there is a large amount of refrigerant in the refrigerating apparatus and the degree of supercooling at the outlet of the condenser 2 becomes large, the pressure reduction in the capillary tube 3 becomes small, the temperature of the refrigerant in the intermediate pressure pipe 8 rises, and auxiliary heat exchange. The amount of heat exchange in the vessel 7 increases. On the other hand, since the degree of superheat at the inlet of the compressor 1 is controlled to an appropriate value by the electric expansion valve 4, the heat exchange amount in the evaporator 4 is relatively increased by the increase in the heat exchange amount in the auxiliary heat exchanger 8. Enthalpy of the refrigerant entering the liquid receiver 6 decreases and the dryness decreases. Therefore, the amount of the liquid refrigerant entering the receiver increases, and the amount of the liquid refrigerant retained in the receiver increases. On the contrary, when the amount of refrigerant in the refrigeration system is small, the temperature of the refrigerant in the intermediate pipe 8 is low, the amount of heat exchange is small, the amount of liquid refrigerant entering the liquid receiver 6 is reduced, and the liquid refrigerant in the liquid receiver is decreased. Is leaked. Therefore, the amount of refrigerant circulating in the refrigeration system is always controlled appropriately.

Another embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is a block diagram of a refrigerating apparatus according to another embodiment of the present invention, and FIG. 4 is a Mollier diagram showing the operation of the refrigerating apparatus according to another embodiment of the present invention.

In FIG. 3, the intermediate pressure pipe 8 of the auxiliary heat exchanger 7 is made thin in place of the capillary tube of FIG. 1 so as to have resistance.

With this structure, the refrigerant in the intermediate pressure pipe 8 of the auxiliary heat exchanger 7 gradually exchanges heat with the low pressure pipe 9 from the state of pressure P1 and enthalpy h2 as shown in FIG. The pressure drops to P2 and enthalpy h3, and the same effect as the embodiment is obtained. Further, in the present embodiment, the first pressure reducer is not necessary and the pressure in the intermediate pressure pipe 8 is reduced, so the temperature difference with the refrigerant in the low pressure pipe 9 is high,
The size of the auxiliary heat exchanger 7 can be reduced.

In this embodiment, R13 is used as the high boiling point refrigerant.
4a, R32 is used as the low boiling point refrigerant, but the same effect can be obtained by using another refrigerant or a mixed refrigerant of three or more kinds.

[0022]

According to the present invention, first, the dryness of the evaporator inlet can be reduced by the auxiliary heat exchanger, the evaporation pressure can be increased even at the same evaporation temperature, and the capacity at low temperature can be improved. .

Secondly, by providing a liquid receiver at the evaporator outlet, the liquid refrigerant having a higher composition of the high boiling point refrigerant can be retained as the evaporation temperature lowers, and the composition of the low boiling point refrigerant in the refrigerating apparatus can be retained. And the refrigerating capacity can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a refrigerating apparatus according to an embodiment of the present invention.

FIG. 2 is a Mollier diagram of an example of the present invention.

FIG. 3 is a block diagram of a refrigerating apparatus according to another embodiment of the present invention.

FIG. 4 is a Mollier diagram of another embodiment of the present invention.

[Explanation of symbols]

1 ... Compressor, 2 ... Condenser, 3 ... Capillary tube, 4
... electric expansion valve, 5 ... evaporator, 6 ... liquid receiver, 8 ... auxiliary heat exchanger.

Claims (1)

[Claims] 1. A refrigeration system in which a compressor, a condenser, a decompressor, and an evaporator are connected to each other and a non-azeotropic mixed refrigerant is enclosed, and a first decompressor and a second decompressor are provided as the decompressor. A refrigerating apparatus comprising: an auxiliary heat exchanger for exchanging heat between the mixed refrigerant between the first pressure reducer and the second pressure reducer and the mixed refrigerant at the evaporator outlet.