JPH07332814A - Heat pump system - Google Patents

Abstract

(57) [Summary] [Purpose] In a refrigeration cycle of a heat pump system using a non-azeotropic mixed refrigerant, a sub-expansion valve, a gas-liquid separator, and a main expansion valve were installed, and frost was formed during low-temperature outdoor air in winter. Even in such a case, the defrost operation can be performed without changing the operation mode, the defrost time can be shortened, and the capacity can be increased at the initial stage of the heating operation restart. In a heat pump type refrigeration circuit using a non-azeotropic mixed refrigerant, a sub expansion valve 3, a gas-liquid separator 4 and a main expansion valve 5 are arranged in series between a condenser 2 and an evaporator 6. At the same time, the vapor phase portion 4a of the vapor-liquid separator 4 and the evaporator 6 are connected by the defrosting bypass refrigerant pipe 8 so that the separated vapor phase component can be used for defrosting the outdoor evaporator.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Recently, various heat pump systems using two kinds of mixed refrigerants having different boiling points, that is, a non-azeotropic mixed refrigerant, have been studied.

By the way, when such two kinds of mixed refrigerants having different boiling points are used, frost formation is more likely to occur than in the case of using a single refrigerant such as a CFC type refrigerant R22 due to the non-isothermal property of the refrigerants. There is a problem. That is, for example, as shown in FIG. 4, even in a refrigeration cycle in which the pressure is adjusted to a temperature T ₁ higher than the frost formation limit temperature To at the evaporator outlet, if the refrigerant has non-isothermal properties, the evaporator inlet has a non-isothermal property. The temperature may become T ₂ and may fall below the frost formation limit temperature To, and frost formation at the evaporator inlet becomes particularly noticeable.

Therefore, conventionally, for the purpose of preventing such frost formation at the inlet portion of the evaporator, for example, an actual fair 3-
Japanese Patent No. 38592 proposes a device in which an evaporator is divided into a plurality of parts and a plurality of pressure reducing mechanisms are provided between them.

On the other hand, in Japanese Patent Publication No. 2-12344, a gas-liquid separator is provided in the downstream portion of the condenser, and the gas phase component is liquefied by a sub-condenser to raise the temperature of the refrigerant. A device used for defrosting has been proposed.

[0006]

However, when the evaporator is divided into a plurality of parts as in the invention of Japanese Utility Model Publication No. 3-38592, the evaporation temperature of the evaporator near the inlet portion is inevitably high. There is a concern about problems such as a decrease in capacity due to the fact that it is difficult to divide the evaporator into a plurality of parts in actual use, and in the invention of Japanese Patent Publication No. 2-12344, a sub-condenser is required and the inside of a cycle is required. There is still a problem to be solved, such as the case where the liquid refrigerant from the sub-condenser does not flow to the expansion valve due to the pressure balance of 1.

The present invention provides a sub-expansion valve, a gas-liquid separator and a main expansion valve on the downstream side of the condenser in the refrigeration cycle of the heat pump system using the non-azeotropic mixed refrigerant as described above, and the cold outdoor air in winter When frost is formed on the outdoor evaporator at times such as when defrosting without changing the operation mode by using the gas phase component separated by the gas-liquid separator for defrosting the outdoor evaporator. The
In addition, the purpose is to shorten the defrost time as much as possible and to enable high capacity at the initial stage of restarting heating operation.

[0008]

In order to achieve the object, the present invention comprises the following problem solving means.

That is, the heat pump system of the present invention is, for example, as shown in FIG. 1, in a heat pump type refrigeration circuit using a non-azeotropic mixed refrigerant, a sub-expansion valve 3, between a condenser 2 and an evaporator 6, The gas-liquid separator 4 and the main expansion valve 5 are arranged in series, and the gas phase portion 4a of the gas-liquid separator 4 and the inlet portion of the evaporator 6 are connected via a bypass refrigerant pipe 8. Has been done.

Further, the heat pump system of the present invention has a liquid retaining portion 7 between the evaporator 6 and the compressor 1 having the above-mentioned structure, and the liquid retaining portion 7 and the gas phase portion 4 of the gas-liquid separator 4 are provided.
and a are connected via a bypass refrigerant pipe 9.

Further, in the heat pump system of the present invention, opening / closing valves 12 and 13 are provided in the middle of the bypass refrigerant pipes 8 and 9 in the above-mentioned respective configurations.

[0012]

The present invention has the following actions in correspondence with the above-mentioned configuration.

That is, in the configuration of the heat pump system of the present invention, as described above, in the heat pump type refrigeration circuit using the non-azeotropic mixed refrigerants having different boiling points,
First, the sub-expansion valve 3, the gas-liquid separator 4, and the main expansion valve 5 are arranged in series between the condenser 2 and the evaporator 6 of the refrigeration circuit, and the sub-expansion valve is operated during steady operation without defrosting, for example. The refrigerant from the condenser 2 whose pressure is reduced by the expansion valve 3 is
The gas-liquid separator 4 separates into a gas phase and a liquid phase.

Then, only the liquid-phase refrigerant is flown to the evaporator 6 side, and the vapor-phase refrigerant is retained in the vapor-phase portion 4a.

On the other hand, when defrosting of the evaporator 6 becomes necessary due to the progress of frost formation such as when the outside air is in a low temperature room, the vapor phase portion 4a of the gas-liquid separator 4 and the inlet portion of the evaporator 6 are as described above. And are connected by the bypass refrigerant pipe 8 for defrosting, the high-temperature vapor-phase refrigerant is flown to the evaporator 6 through the bypass refrigerant pipe 8 to perform efficient defrosting in a short time.

In this case, a liquid retaining portion 7 is further provided between the evaporator 6 and the compressor 1, and the liquid retaining portion 7 is connected to the gas phase portion 4a of the gas / liquid separator 4 by the bypass refrigerant pipe 9. Therefore, during steady operation without using the defrosting bypass refrigerant pipe 8, the vapor phase refrigerant of the vapor phase portion 4a of the vapor liquid separator 4 flows into the liquid retaining portion 7 and evaporates. It is mixed with the gas refrigerant from the container 6 and drawn into the compressor 1.

Further, in each of these cases, if the on-off valves 12 and 13 are provided in the middle of the bypass refrigerant pipes 8 and 9, respectively, the opening control of the on-off valves 12 and 13 causes
Appropriate switching control of the vapor phase refrigerant is performed during the steady operation and the defrost operation.

Now, for example, referring to FIG. 1, the operation from the steady operation to the defrost operation will be described with reference to the pressure-composition diagram shown in FIG.

That is, the liquid refrigerant flowing out of the condenser 2 at the pressure Pc is decompressed to the pressure Pd by the auxiliary expansion valve 3 and enters the gas-liquid separator 4 in a gas-liquid two-phase state. At this time, the composition C ₁ of the liquid phase in the gas-liquid separator 4 is richer in the high-boiling point refrigerant than in the gas phase, and the composition is suitable for the operation under the low load condition such that frost is not formed. Therefore, only the liquid refrigerant is reduced to the pressure Pe by the main expansion valve 5, and the evaporator 6
The efficiency of the refrigeration cycle can be improved.

On the other hand, when the outdoor air temperature drops and frost is formed on the outdoor heat exchanger, the defrost operation is performed. In this case, the bypass refrigerant pipe 9 connecting the gas phase part 4a of the gas-liquid separator 4 and the liquid retaining part 7 and the pipe from the gas-liquid separator 4 to the main expansion valve 5 are closed, and the gas-liquid separator is closed. Gas phase part 4a of 4
Only the bypass refrigerant pipe 8 at the inlet of the evaporator 6 connected to the side is opened. Therefore, the relatively high temperature refrigerant in the gas-liquid separator 4 flows through the evaporator 6, and the defrost operation can be completed in a very short time.

The operation during the defrosting operation will be described with reference to the pressure-composition diagram of FIG. 3. Since the gas phase component C ₂ in the gas-liquid separator 4 contains a relatively low boiling point component. The composition of the refrigerant in the liquid retaining portion 7 is C ₃ which is richer in the low boiling point component than in normal operation Co.

Therefore, the heating capacity of the refrigerant flowing into the condenser 2 at the initial stage when the defrost operation is finished and the normal heating operation mode is restored is larger than usual, so that the efficiency of the heating operation can be improved and the defrost operation can be improved. It is also possible to reduce the draft feeling due to the deterioration of the ability.

Further, in the normal defrost operation, it is necessary to reverse the operation mode by switching the four-way valve, which is not necessary in the case of the present invention.

[0024]

As a result of the above, according to the heat pump system of the present invention, the following effects can be obtained.

The refrigeration cycle efficiency during low load operation can be improved.

A reduction in draft feeling and an improvement in heating operation efficiency are realized by shortening the defrost operation time.

It is possible to increase the heating capacity at the initial stage of the heating operation restart.

[0028]

1 to 3 show the construction and operation of a refrigeration circuit of a compression heat pump system using a non-azeotropic mixed refrigerant according to an embodiment of the present invention.

First, FIG. 1 shows the configuration of the refrigeration circuit. The refrigeration circuit includes a compressor 1, a condenser 2, an auxiliary expansion valve 3, a gas-liquid separator 4, a main expansion valve 5, an evaporator 6, and a liquid retaining portion 7.
Are connected in series in this order from the refrigerant discharge port side of the compressor 1 to the refrigerant suction port side via a main refrigerant pipe, and two types of refrigerants having different boiling points are provided in the circuit. A non-azeotropic mixed refrigerant formed by mixing (hereinafter, simply referred to as a refrigerant) is enclosed in a certain amount, and the heat pump function by circulating the refrigerant from liquid to gas, and from gas to liquid while repeatedly changing phases. It has come to be realized.

On the other hand, in the structure, the gas-liquid separator 4 is used.
The gas phase portion 4a is connected to the inlet portion of the evaporator 6 via the first bypass refrigerant pipe 8 provided with the first opening / closing valve 12 and the second opening / closing valve 13 is provided. It is connected to the liquid retaining portion 7 via the second bypass refrigerant pipe 9.

Next, each operation of the refrigeration circuit during steady operation and defrost operation will be described with reference to the pressure-composition diagrams of FIGS. 2 and 3.

(1) Operation of Refrigeration Cycle during Steady Operation In the refrigeration cycle in the steady operation without defrost operation, the first passage from the gas-liquid separator 4 vapor phase portion 4a serving as the bypass passage of the evaporator 6 is performed. The bypass refrigerant pipe 8 (broken line in FIG. 1) is closed by a first opening / closing valve 12. Therefore, the refrigerant decompressed by the sub-expansion valve 3 is separated into a gas phase and a liquid phase in the gas-liquid separator 4, and only the liquid-phase refrigerant flows through the main expansion valve 5 to the evaporator 6 side. The phase refrigerant flows into the liquid retaining portion 7 via the second bypass refrigerant pipe 9.

That is, assuming that the pressure of the liquid refrigerant A flowing out of the condenser 2 in FIG. 1 is Pc and the composition ratio (circulation composition ratio) is Co, the liquid refrigerant A having the pressure Pc and the composition ratio Co is Refrigerant B in the gas-liquid two-phase state (gas-phase side composition ratio C ₂ , liquid-phase side composition ratio C ₁ ) after being primarily reduced to pressure Pd at the sub-expansion valve 3
And flows into the gas-liquid separator 4, and the composition ratio C ₂ , C ₁
Of the gas phase refrigerant D and the liquid refrigerant C.

Then, the vapor phase refrigerant D (composition ratio C
₂ ) is directly returned to the compressor 1 side liquid retaining portion 7 via the second bypass refrigerant pipe 9 by opening the second opening / closing valve 13.
The vapor-phase refrigerant D returned to the liquid retaining portion 7 is the liquid retaining portion 7
Inside, it is mixed with the gas refrigerant G from the evaporator 6 to become a refrigerant F having a pressure Pg and a composition ratio Co, and is sucked into the compressor 1.

Then, the refrigerant H having the above composition ratio Co which is compressed by the compressor 1 and liquefied is supplied to the condenser 2 again.

On the other hand, the liquid refrigerant C separated from the gas-phase refrigerant D in the gas-liquid separator 4 and remaining in the liquid-phase portion 4b is secondarily decompressed by the main expansion valve 5 so that the pressure Pc, It becomes a gas-liquid two-phase refrigerant E having a composition ratio C ₁ . Then, the gas-liquid two-phase refrigerant E is supplied to the evaporator 6 via the flow rate adjusting valve 11 and evaporated to become a gas refrigerant G, which is supplied to the liquid retaining portion 7.
As described above, after being mixed with the gas-phase refrigerant D from the gas-phase portion 4a of the gas-liquid separator 4, it is sucked into the compressor 1.

As described above, the liquid refrigerant A flowing out of the condenser 2 at the pressure Pc is decompressed to the pressure Pd by the sub-expansion valve 3 to be in the gas-liquid two-phase state and then flow into the gas-liquid separator 4. At this time, the composition of the liquid phase in the gas-liquid separator 4 is rich in the high-boiling-point refrigerant as compared with the gas phase, and the composition of the composition is suitable for the operation under the low load condition such that frost is not formed. Therefore, the efficiency of the refrigeration cycle can be improved by reducing only this liquid refrigerant to the pressure Pe by the main expansion valve 5 and allowing it to flow into the evaporator 6 (see FIG. 2).

(2) Refrigeration cycle in the case of defrost operation On the other hand, when the outside air temperature drops and frost forms on the outdoor heat exchanger, the defrost operation is performed. In this case, the second bypass refrigerant pipe 9 connecting the gas-liquid separator 4 and the liquid retaining portion 7 and the pipe from the gas-liquid separator 4 to the main expansion valve 5 are closed, and the gas-liquid separator 4 is closed. Evaporator 6 connected to the gas phase portion 4a side
Only the first bypass refrigerant pipe 8 on the inlet side is opened.

As a result, a high-temperature gas-phase refrigerant (pressure Pd, composition ratio C ₂ ) D is made to flow into the evaporator 6 from the gas-phase portion 4a of the gas-liquid separator 4, and defrost in a very short time. Is done.

Then, the vapor-phase refrigerant after the completion of the defrosting
(Composition ratio C ₂ ) G is supplied to the liquid retaining portion 7. At this time, the liquid retaining portion 7 stores the refrigerant having a low boiling point component with a pressure Pg and a composition ratio C ₃ .

At the beginning of the subsequent restart, the stored refrigerant having a low boiling point component (composition ratio C ₃ ) is sucked into the compressor 1 and supplied to the condenser 2. The condensing capacity of the vessel 2 will be increased.

After a lapse of a predetermined operation time, the composition of the refrigerant in the condenser 2 becomes constant (Co), and the steady operation is performed.

Now, the operation during the above defrost operation is shown in FIG.
Describing with reference to the pressure-composition diagram of the above, since the gas phase component C ₂ in the gas-liquid separator 4 contains a relatively low boiling point component as described above, The composition becomes C ₃ in which the low boiling point component is richer than in the steady operation (composition ratio Co). Therefore, the heating capacity of the refrigerant flowing into the condenser 2 at the initial stage of the restart of the heating operation becomes larger than usual, the efficiency of the heating operation can be improved, and the draft feeling due to the capacity decrease at the time of defrosting can be reduced. It will be possible. Further, in the normal defrost operation, it is generally necessary to reverse the operation mode by switching the four-way valve, but in the case of the present invention, this is not necessary.

Needless to say, the defrost bypass refrigerant pipe 8 from the vapor phase portion 4a to the evaporator 6 may be provided separately for each path of the evaporator 6, for example.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a refrigeration circuit of a heat pump system according to an embodiment of the present invention.

FIG. 2 is a refrigerant pressure-composition diagram during steady operation of the heat pump system.

FIG. 3 is a refrigerant pressure-composition diagram during defrost operation of the heat pump system.

FIG. 4 is a refrigerant diagram illustrating a frosting phenomenon due to a temperature change of a non-azeotropic mixed refrigerant in a conventional heat pump system.

[Explanation of symbols]

1 is a compressor, 2 is a condenser, 3 is an auxiliary expansion valve, 4 is a gas-liquid separator, 4a is a gas phase part, 5 is a main expansion valve, 6 is an evaporator, 7 is a liquid retaining part, and 8 is a first Is a second bypass refrigerant pipe, 12 is a first opening / closing valve, and 13 is a second opening / closing valve.

Claims (3)

[Claims] 1. In a heat pump type refrigeration circuit using a non-azeotropic mixed refrigerant, a sub-expansion valve (3), a gas-liquid separator (4), a main unit are provided between a condenser (2) and an evaporator (6). The expansion valves (5) are arranged in series and the gas phase part (4) of the gas-liquid separator (4) is
A heat pump system characterized in that a) and the inlet of the evaporator (6) are connected via a bypass refrigerant pipe (8). 2. A liquid retaining part between the evaporator (6) and the compressor (1).
(7), characterized in that the liquid retaining part (7) and the gas phase part (4a) of the gas-liquid separator (4) are connected via a bypass refrigerant pipe (9). The heat pump system according to claim 1. 3. The heat pump system according to claim 1, wherein opening / closing valves (12) and (13) are provided in the middle of the bypass refrigerant pipes (8) and (9), respectively.