JPH03263555A - Multiple refrigerating machine - Google Patents

Abstract

PURPOSE:To make an expansion tank on a low pressure pipe of a low temperature side refrigerating cycle small in size by a method wherein a bypass pipe leading to a high pressure side pipe is connected to the expansion tank, and a control valve, which is opened when a compressor is stopped, is provided on the bypass pipe. CONSTITUTION:When cooling operation is stopped, a control valve is opened to make the liquid refrigerant in a condenser 21 flow into an expansion tank 30 and low pressure side pipes of a refrigerating cycle through a bypass pipe 31. That is, the liquid refrigerant flows into the expansion tank 30 and the low pressure side pipes which are low in temperature when operation is stopped, so that vaporizing of the refrigerant is prevented. Thereby, an increase in the refrigerant pressure can be restricted to a minimum, and the expansion tank can be reduced in size.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-component refrigeration system that exchanges heat between an evaporator in a high-temperature refrigeration cycle and a condenser in a low-temperature refrigeration cycle.

(Note) As a demonstration of the conventional technology dual refrigeration equipment,
There is a publication No. 72. In this publication, heat is exchanged between the evaporator of the high temperature side refrigeration cycle and the condenser of the low temperature side refrigeration cycle using a cascade condenser, and the low temperature side refrigeration cycle is provided with an expansion tank.

In such a binary refrigeration system, when the operation is stopped, the refrigerant present in the low-temperature side refrigeration cycle is gasified and the pressure of this low-temperature side refrigeration cycle increases, but it is difficult to guide the gasified refrigerant to the expansion tank. This is to reduce the pressure rise.

(c) Problems to be Solved by the Invention Since the gasified refrigerant is guided into the expansion tank in order to keep the pressure rise low, the capacity of the expansion tank sometimes becomes large.

The object of the present invention is to reduce the size of the expansion tank by gasifying the refrigerant in the low-temperature side refrigeration cycle when the operation is stopped.

(d) Means for Solving the Problems In order to achieve this object, the present invention connects an expansion tank to the low-pressure side pipe line of the low-temperature side refrigeration cycle of a multi-component refrigeration system, and also connects the expansion tank to the low-pressure side refrigeration cycle of the multi-component refrigeration system. A bypass pipe connected to the high-pressure side pipe line of the cycle is provided, and a control valve that can be fully opened when the operation is stopped is arranged in this bypass pipe.

(*) By opening the control valve when the operation is stopped, the liquid refrigerant in the condenser flows into the expansion tank. Here, this expansion tank is cooled because it is on the low pressure side of the low temperature side refrigeration cycle, and the liquid refrigerant flowing into this expansion tank is difficult to gasify and the pressure increase of the refrigerant can be suppressed to a low level.

(F) Embodiment In FIGS. 1 and 2, reference numeral 1 denotes a binary refrigeration system, which is composed of a high-temperature side unit 2, a low-temperature side unit 3, and a cooler unit 4. These units 2, 3.4 are connected by a refrigerant pipe (described later).

5 is a high temperature side refrigeration cycle, which includes a compressor 6, a muffler 7, a condenser 8, a first liquid receiver 9, a dryer 10, a first control valve 11,
A first expansion valve (pressure reducer) 12, a subcooler 13 functioning as a subcooler, an evaporator 14, and an accumulator 15 are connected in this order through a refrigerant pipe. The refrigerant sealed in this high temperature side refrigeration cycle 5 is R-22. 16 is a temperature sensor attached to the low pressure side piping, and the opening degree of the first expansion valve 120 is controlled based on the temperature detected by the sensor 16. Further, the first control valve 11 is closed during the pump-down operation performed after the cooling operation of the refrigeration cycle 5 is stopped, and the refrigerant in the evaporator 14 is transferred to the high-pressure side pipes (condenser 8 etc.) of the refrigeration cycle 5. It is to be collected by

17 is a low temperature side refrigeration cycle, which includes a compressor 18 and a muffler 19.
, oil separator 20, condenser 21, second liquid receiver 3
4, a subcooler 13, a dryer 22, a second expansion valve (pressure reducer) 23, an evaporator 24, a suction pressure regulating valve 25, and an accumulator 26 are connected in this order through cold tubes. An oil return pipe 27 returns the oil stored in the oil separator 20 to the compressor 18. The condenser 21 of the low temperature side refrigeration cycle 17 and the evaporator 14 of the high temperature side refrigeration cycle 5 are integrally combined by a cascade condenser 28. The evaporator 14 of No. 5 exchanges heat with the evaporator 14 of No. 5.

The refrigerant sealed in this low temperature side refrigeration cycle 17 is R
-13. Reference numeral 29 denotes a temperature sensor attached to the low pressure side piping, and the opening degree of the second expansion valve 23 is controlled based on the temperature detected by this sensor 29. 30 is an expansion tank;
Reference numeral 31 designates one bypass pipe, one end of which is connected to the inlet side of the condenser 21, that is, the high-pressure side pipe line 32, and the other end connected to the upper part of the expansion tank 30. Reference numeral 33 designates a second control valve provided on one of the bypass pipes 31, which is closed when the compressor 18 of the low-temperature side refrigeration cycle 17 is in operation, and opened when the compressor 18 of the low temperature side refrigeration cycle 17 is stopped. This second control valve 33 is a solenoid valve that is generally called a one-current open type. 35 is the other bypass pipe,
One end is connected to the lower part of the expansion tank 30, and the other end is connected to the inlet side of the suction pressure regulating valve 25, that is, the low pressure side pipe line. Since the second control valve 33 is opened when the compressor 18 is stopped, the liquid refrigerant in the condenser 21 of the low temperature side refrigeration cycle 17 is transferred to the high pressure side pipe 32,
It is guided to the expansion tank 30 via one bypass pipe 31. The above-mentioned suction pressure regulating valve 25 has an inlet side pipe line 36.
If the refrigerant pressure in the refrigerant is, for example, 5 kg/cm or more, the opening degree of the valve 25 is reduced to reduce the refrigerant pressure by about 5 kg, and the refrigerant is returned to the compressor 18. This prevents the pressure of the refrigerant sucked into the compressor 1B from becoming abnormally high, thereby preventing the (high) pressure of the refrigerant discharged from the compressor 1B from increasing abnormally. 39 is a delay device. (delay means), the compressor 6 of the high temperature side refrigeration cycle 5 and the compressor 1 of the low temperature side refrigeration cycle 17.
8 and is connected to the compressor 6 of the high temperature side refrigeration cycle 5.
A signal is sent to the compressor 1B so that the compressor 18 of the low temperature side refrigeration cycle 17 starts operating 60 seconds after the start of operation.

A binary refrigeration system with such a configuration is particularly suitable for the high temperature side unit 2.
The high temperature side unit 2 has a built-in compressor 6 and condenser 8 of the high temperature side refrigeration cycle 5, and the low temperature side unit 3 has a cascade condenser 28 and a cooler unit 4. The compressor 1B of the low temperature side refrigeration cycle 17 is built in, and the evaporator 24 of the low temperature side refrigeration cycle 17 is built in the cooler unit 4. By doing this, the freezer compartment equipped with the cooler unit 4 (
(not shown), if there is no space to place both the low-temperature side unit 3 and the high-temperature side unit 2, place only the low-temperature side unit 3 near this freezer compartment, and place the high-temperature side unit 2 in another location. You can also put Here, the temperature of the low-temperature side inter-unit piping 37 that connects the low-temperature side unit 3 and the cooler unit 4 (the temperature of the refrigerant flowing inside the low-temperature side inter-unit piping 37) is the same as that between the high-temperature side unit 2 and the low-temperature side unit Although the temperature of the inter-unit piping 38 on the high-temperature side connecting the Since the distance between side unit 3 and cooler unit 4 is short), this inter-unit piping 3
7 can be reduced. Further, if there is space near the freezer compartment, the high temperature side unit 2 and the low temperature side unit 3 may be arranged side by side as shown in FIG. Furthermore, the low temperature side unit 3 and the cooler unit 4 may be combined integrally, and only the high temperature side unit 2 may be separated.

Next, the operating state of this binary refrigeration system 1 will be explained. At the start of operation, first the compressor 6 of the high temperature side refrigeration cycle 5 is
is operated, the first control valve 11 is opened, and the refrigerant is allowed to flow as indicated by the solid line arrow in FIG.

Here, before the start of this operation, that is, before the end of the previous operation, the first control valve 11 is closed to perform a pump-down operation, and the refrigerant in the evaporator 14 is recovered to the high-pressure side pipe of the condenser 8, etc. . Therefore, since the operation starts with no refrigerant in the evaporator 14, the evaporator 14 is quickly cooled by the cold coke that flows after the start. And delay device 3
9, the compressor 18 of the low temperature side refrigeration cycle 17 starts operating after 60 seconds (predetermined time) has elapsed from the start of operation of the compressor 6 of the high temperature side refrigeration cycle 5.

In this way, the delay device 39 delays the start of operation of the compressor 18 of the low temperature side refrigeration cycle 17 and the start of operation of the compressor 18 of the low temperature side refrigeration cycle 17.
The reason why the start of operation of the compressor 6 was delayed was because we wanted to first lower the temperature of the evaporator 14 of the high-temperature side refrigeration cycle 5 to a certain extent before flowing the refrigerant into the condenser 21 of the low-temperature side refrigeration cycle 17. . This shortens the start-up time of the low temperature side refrigeration cycle 17. Moreover, the temperature of the evaporator 14 of the high-temperature side refrigeration cycle 5 can be lowered to a certain degree by this predetermined time, and thereby the heat exchange capacity of the cascade condenser 28 can be kept constant. This predetermined time can be varied depending on the length of the dual refrigeration system.

Instead of the delay device 39 described above, a temperature sensor is attached to the outlet pipe of the evaporator 14 of the high temperature side refrigeration cycle 5, and when the temperature detected by this sensor falls below a certain value, the compressor 18 of the low temperature side refrigeration cycle 17 is operated. I also thought about letting him do it.

However, as described above, due to the pump-down operation, refrigerant flows into the evaporator 14 from a state where there is no refrigerant immediately after the start of operation, so the temperature of the outlet pipe of the evaporator 14 rapidly decreases (for several seconds). (changes from 30°C to 0°C). The temperature sensor could not keep up with such sudden changes, and the compressor 1 of the low temperature side refrigeration cycle 17
There is a possibility that the instruction to start operation in step 8 may not be given accurately.

In this way, both compressors 6 and 18 start operating to cool the freezer compartment in which the evaporator 24 of the low-temperature side refrigeration cycle 17 is housed. Here, the low temperature side refrigeration cycle 17
Although most of the refrigerant discharged from the compressor 18 is condensed and liquefied in the condenser 21 in the cascade condenser 28, some of the refrigerant is not liquefied and remains in the condenser 21.
It may be leaked from. The gas refrigerant in such a case is stored in the upper part of the second liquid receiver 34. The liquid refrigerant flowing out from the liquid receiver 34 flows into the subcooler 13. The liquid refrigerant is completely cooled to a supercooled state in the subcooler 13, and is then subjected to a pressure reducing action by the second expansion valve 23. In this way, the liquid refrigerant discharged from the condenser 21 is transferred to the second
The liquid is stored in the liquid receiver 34, supercooled by the subcooler 13, and then flowed to the second expansion valve 23, so that the flash gas flows into the second expansion valve 23, and the second expansion valve 2
There is no risk of destabilizing the operation (valve opening) of item 3.
Therefore, it is possible to improve the operating condition of the second expansion valve 23 and obtain stable refrigerating capacity. Also, since the boiling point of the refrigerant (R-13) in the low-temperature side refrigeration cycle 17 is higher than that of the refrigerant (R-22) in the high-temperature side refrigeration cycle, it is easily gasified, but the subcooler 13 brings the refrigerant into a supercooled state. By doing so, this gasification can be assisted in advance and the expansion tank 30 can be downsized.

Since a suction pressure regulating valve 25 is provided in the suction pipe of the compressor 18 of the low-temperature side refrigeration cycle 17, if the setting value of this regulating valve 25 is set to, for example, 5 kg/cm, the pressure near the evaporator 24 is set by this regulating valve. Refrigerant pressure of 5 kg/cm
``Even if the pressure of the refrigerant drawn into the compressor 18 is maintained at 5 kg/cm''
Since the pressure of the refrigerant sucked into the refrigerant 8 is prevented from exceeding a predetermined value by the regulating valve 25, the pressure difference between high and low pressures in the low-temperature side refrigeration cycle 17 can be quickly kept constant. Incidentally, if such a suction pressure regulating valve 25 is not provided, it will take a long time to maintain a constant pressure difference between high and low pressures. In addition, there was a risk that stable refrigeration capacity could not be exerted promptly.

Next, when the cooling operation is stopped, the second control valve 33 is opened (it is closed during the cooling operation), and the liquid refrigerant in the condenser 21 is guided to the expansion tank 30 via the bypass pipe 31. In this way, when the cooling operation is stopped, the liquid refrigerant in the condenser 21 of the low temperature side refrigeration cycle 17 is flowed into the expansion tank 30 and the low pressure side piping of this refrigeration cycle. That is, the liquid refrigerant is poured into the expansion tank 30 and the low-pressure side piping, which are at a low temperature when the operation is stopped, to suppress vaporization of the liquid refrigerant as much as possible. As a result, the pressure increase of the refrigerant at the time of shutdown is suppressed to a small level, and the expansion tank 30 can be made smaller.

Furthermore, after the cooling operation is finished, the compressor 18 of the low-temperature side refrigeration cycle 17 is stopped, and the compressor 6 of the high-temperature side refrigeration cycle 5 is stopped.
The operation continues, and the first control valve 11 is closed to perform pump-down operation. By this pump-down operation, the refrigerant in the subcooler 13 and the evaporator 14 is completely recovered to the high-pressure side pipe line of the condenser 8, etc., and the evaporator 14 becomes free of refrigerant. Therefore, when the cooling operation is restarted (the operation of the compressor 6 of the high temperature side refrigeration cycle 5 is restarted), the evaporator 14 is quickly cooled by the refrigerant flowing into the evaporator 14 at the same time as the restart. As a result, the compressor 18 of the low temperature side refrigeration cycle 17
When the operation of the compressor 18 is restarted, the refrigerant discharged from the compressor 18 is quickly cooled down in the condenser 21.

(G) Effects of the Invention As described above, the present invention provides a bypass pipe connected to the high pressure side pipe of the low temperature side refrigeration cycle in the expansion tank provided to the low pressure side pipe of the low temperature side refrigeration cycle of a multi-component refrigeration system. Moreover, since a control valve that is opened when the operation is stopped is arranged in this bypass pipe, the liquid refrigerant in the condenser flows into the cooling expansion tank when the operation is stopped, thereby suppressing gasification of the liquid refrigerant. As a result, the pressure increase of the refrigerant is suppressed to a low level, and the expansion tank can be made smaller.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a refrigerant circuit diagram of a binary refrigeration system, and FIG. 2 is a perspective view showing a state in which a high temperature side unit and a low temperature side unit of this system are arranged. 5... High temperature side refrigeration cycle, 14... Evaporator,
17... Low temperature side refrigeration cycle, 21... Condenser,
30... Expansion tank, 31... Bypass pipe, 3
3...Control valve.

Claims (1)

[Claims] 1) In a multicomponent refrigeration system in which the evaporator of the high-temperature side refrigeration cycle and the condenser of the low-temperature side refrigeration cycle are exchanged heat, and an expansion tank is provided in the low-pressure side pipe line of the low-temperature side refrigeration cycle, this expansion tank is A multi-component refrigeration system, characterized in that a bypass pipe is connected to the high-pressure side pipe line of the low-temperature side refrigeration cycle, and a control valve that is opened when the compressor of the low-temperature side refrigeration cycle is stopped is arranged in the bypass pipe. Device.