JPH073247Y2 - 2-axis 2-stage refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention mainly relates to a two-shaft two-stage refrigeration system using screw type compressors installed in parallel, more specifically, a low-stage side compressor having a drive device, A high-stage compressor having a drive device is provided to switch between a two-stage compression operation that drives both the high-stage and low-stage compressors and a single-stage compression operation that drives only the high-stage compressor. The present invention relates to a possible two-shaft two-stage refrigeration system.

(Prior Art) Conventionally, as this type of two-shaft two-stage refrigeration system, by returning the intermediate-pressure gas refrigerant evaporated in the intercooler between the low-stage compressor and the high-stage compressor, evaporation is performed. The one in which the liquid refrigerant sent to the vessel is subcooled to improve the operation efficiency is known, for example, from FIG. 1 of Japanese Utility Model Publication No. Sho 55-22442.

Further, in the single-stage refrigeration system, the one that obtains the same effect as that described above by supplying the intermediate pressure part of the compressor with the intermediate-pressure gas refrigerant evaporated in the intermediate cooler is disclosed in, for example, It is known from Japanese Patent No. 59-42614.

By the way, in the two-shaft two-stage refrigeration system which can switch the single-stage or two-stage compression operation using the high and low stage compressors as described above, in order to improve the operation efficiency in each of these operations, the above-mentioned intermediate At the outlet side of the cooler, a first intermediate pressure gas pipe reaching the middle of each compressor and a second intermediate pressure gas pipe reaching an intermediate portion of the high-stage compressor are connected, respectively, and each compression is performed. Of the intermediate pressure gas pipes by selectively opening each of the intermediate pressure gas pipes during a two-stage compression operation using both the compressors and during a single-stage operation using only the high-pressure side compressor. Therefore, it was considered to supply an intermediate pressure gas refrigerant.

That is, as shown in FIG. 2, a low stage compressor (1) having a drive unit (2) and a high stage compressor (3) also having a drive unit (4) are provided, and Low-stage compressor (1)
Suction pipe (5) is connected to the suction port (1a) side, and the discharge port (1b) of the low-stage compressor (1) is connected to the suction port (3a) of the high-stage compressor (3). A bypass pipe (7) for bypassing the low-stage compressor (1) is connected between the suction pipe (5) and the communication pipe (6) while connecting through the communication pipe (6). On the other hand, the bypass pipe (7) is provided with a solenoid valve (8) which is opened during single-stage operation and closed during two-stage operation.

Further, a condenser (10), an expansion valve (11) and an evaporator (12) are connected to the discharge port (3b) side of the high pressure side compressor (3), and the condenser (10) and An intermediate cooler (13) is provided at an intermediate portion between the evaporator (12) and the refrigerant inlet side of the intermediate cooler (13) via the intermediate expansion valve (14) to the condenser (10). A first intermediate pressure gas pipe (16) connected to the outlet part and on the refrigerant outlet side of the intermediate cooler (13), which is connected to the communication pipe (6), and the high pressure side compressor (3). While connecting the second intermediate pressure gas pipe (17) connected to the intermediate part of
First and second electromagnetic valves (V1) and (V2) are provided at intermediate portions of the intermediate pressure gas pipes (16) and (17), respectively.

Thus, when the load condition of the refrigeration system is a high compression ratio and both the high and low stage side compressors (1) and (3) are driven to perform the two stage compression operation, the first stage By closing the solenoid valve (8), the refrigerant from the suction pipe (5) is transferred from the low pressure side compressor (1) to the connecting pipe (6) to the high pressure stage as indicated by the solid arrow in the figure. The refrigerant is advected in the path of the side compressor (3), and the high- and low-stage side compressors (1) and (3) perform two-stage compression of the refrigerant.

Further, during the above two-stage compression operation, the second solenoid valve (V2) of the second intermediate pressure gas pipe (17) is closed, and the first solenoid valve of the first intermediate pressure gas pipe (16) ( By opening V1), the intermediate-pressure gas refrigerant evaporated in the intermediate cooler (13) is returned to the communication pipe (6) via the first intermediate-pressure gas pipe (16).

Further, when the load condition of the refrigerating apparatus is a low compression ratio, only the high-stage compressor (3) is driven, and the single-stage compression operation is performed, the solenoid valve (8) is opened. As a result, the refrigerant from the suction pipe (5) is transferred from the solenoid valve (8) to the bypass pipe (7) as indicated by the dotted arrow in the figure.
-> The connecting pipe (6)-> High-stage side compressor (3) is advected in the path, and the high-stage side compressor (3) alone compresses the refrigerant.

Further, during the single-stage compression operation as described above, the first solenoid valve (V1) of the first intermediate pressure gas pipe (16) is closed, and the second solenoid valve of the second intermediate pressure gas pipe (17) ( By opening V2), the intermediate-pressure gas refrigerant evaporated in the intermediate cooler (13) is passed through the second intermediate-pressure gas pipe (17) to the intermediate portion of the high-stage compressor (3). Return to.

(Problems to be solved by the invention) By the way, as described above, the first and second intermediate pressure gas pipes (16, 17) are connected to the outlet side of the intermediate cooler (13), respectively. When the first and second solenoid valves (V1) (V2) are installed in the pressure gas pipes (16) (17), the solenoid valves (V1) (V2) are controlled to open and close individually. However, there is a problem that the structure becomes complicated and the cost becomes high.

The present invention has been made in view of the above problems, and an object thereof is to replace one of the solenoid valves with a check valve to simplify the structure and reduce the cost.
It is intended to provide a two-stage shaft refrigeration system.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a low-stage compressor (1) having a drive device (2) and a drive device (4).
And a suction stage (1) of the low-stage compressor (1), and a suction pipe (5) is connected to the low-stage compressor (1). The discharge port (1b) is connected to the suction port (3a) of the high-pressure stage compressor (3) by a connecting pipe (6), and an intercooler (13) is provided, and the outlet of the intercooler (13). On the side, a first intermediate pressure gas pipe (16) connected to the communication pipe (6) and a second intermediate pressure gas pipe (17) connected to the intermediate portion of the high-stage compressor (3) are connected. In the two-shaft two-stage refrigeration system described above, the opening / closing valve (1
8) and a check valve (19) is provided in the second intermediate pressure gas pipe (17) to allow only the flow to the intermediate portion of the high pressure side compressor (3).

(Operation) In the two-shaft two-stage refrigeration system as described above, the two-stage compression operation using both the high and low stage compressors (1) and (3) and the high stage compressor (3) When performing the single-stage compression operation using only the open / close valve (18) provided in the first intermediate pressure gas pipe (16) extending from the outlet side of the intermediate cooler (13), the on / off valve (18) is opened / closed, The second intermediate pressure gas pipe (1
The check valve (19) interposed in 7) is automatically opened and closed based on the pressure difference of the refrigerant advancing through the suction pipe (5) and the communication pipe (6). , So the following is a brief description.

First, when the load condition of the refrigeration system is a high compression ratio and the two-stage compression operation is performed using both the high and low stage side compressors (1) and (3), the check valve (19 ) Is closed,
Moreover, the on-off valve (18) is opened, and the intermediate-pressure gas refrigerant evaporated in the intermediate cooler (13) is passed through the first intermediate-pressure gas pipe (16) to the communication pipe (6). Will be returned.

Further, when the load condition is a low compression ratio and the single-stage compression operation is performed using only the high-stage compressor (3), the opening / closing valve (18) is closed and the check valve ( 19) is automatically opened, and the intermediate-pressure gas refrigerant evaporated in the intermediate cooler (13) is passed through the second intermediate-pressure gas pipe (17) to the high-stage compressor (3). It is returned only to the intermediate part of.

(Embodiment) FIG. 1 shows a piping diagram of a two-shaft two-stage refrigeration system, in which (1) is a screw type low-stage compressor (D) equipped with a drive unit (2) composed of a motor. 1) and 3) are screw-type high-stage compressors equipped with a drive device (4) also composed of a motor, and a suction pipe (1a) is attached to a suction port (1a) of the low-stage compressor (1). 5) is connected, and the discharge port (1b) of the low-stage compressor (1) is connected to the high-stage compressor (3).
Bypass for connecting the low-stage compressor (1) between the suction pipe (5) and the communication pipe (6) while connecting to the suction port (3a) of the same through the communication pipe (6). While connecting the pipe (7), the connecting pipe (6) and the bypass pipe (7) are automatically connected to each other by a pressure difference between the suction pipe (5), the connecting pipe (6) and the bypass pipe (7). First and second check valves (9a) and (9b) that are opened and closed are interposed.

Further, a condenser (10), an expansion valve (11) and an evaporator (12) are connected to the discharge port (3b) of the high-stage side compressor (3) via a discharge pipe (15). In addition, at the intermediate portion between the condenser (10) and the evaporator (12), an intercooler (1
3) is interposed, and the refrigerant inlet side of the intercooler (13) and the outlet of the condenser (10) are connected via an inflow pipe (14a) provided with an intermediate expansion valve (14), While part of the refrigerant liquid condensed in the condenser (10) is cooled by the intercooler (13), the connecting pipe (6) is provided on the refrigerant gas outlet side of the intercooler (13). ) Connected to a first intermediate pressure gas pipe (16) and a second intermediate pressure gas pipe (17) connected to an intermediate portion of the high pressure side compressor (3).

Thus, in the two-shaft two-stage refrigeration system as described above, an opening / closing valve (18) mainly composed of a solenoid valve is provided at an intermediate portion of the first intermediate pressure gas pipe (16), and the second intermediate pressure gas is provided. A check valve (19) that is automatically opened and closed by the pressure difference of the gas refrigerant is provided in the middle of the pipe (17).

The check valve (19) includes the suction pipe (5) and the communication pipe (6).
Is automatically opened / closed based on the pressure difference of the gas refrigerant advancing, and prior to explaining the switching operation of the check valve (19), the pressure code of each part shown in FIG. Will be described.

(P1) is the pressure of the refrigerant advected in the suction pipe (5),
(P2) is the pressure of the refrigerant in the discharge region discharged from the discharge port (1b) side of the low-pressure stage compressor (1), and (P3) is the check valve (2) in the second intermediate pressure gas pipe (17). The refrigerant pressure at the connection point to the high-stage compressor (3) on the refrigerant outflow side of 19), (P4) is the discharge port (3b) of the high-stage compressor (3)
The pressure of the refrigerant discharged from the fuel cell, and (P5) indicates the pressure of the refrigerant on the outlet side of the intercooler (13).

However, in the case where the load condition of the refrigeration system is a high compression ratio,
When performing the two-stage compression operation using both the high- and low-stage compressors (1) and (3), the on-off valve (18) is opened. At this time, each of the compressors is operated. (1)
With the driving of (3), the pressure (P4) of the refrigerant discharged from the discharge port (3b) side of the high pressure side compressor (3) becomes the highest, and with respect to this discharge pressure (P4) , The pressure (P3) of the refrigerant at the connection portion of the second intermediate pressure gas pipe (16) to the high-pressure stage compressor (3) becomes slightly low, and subsequently,
The pressure of the refrigerant discharged from the discharge port (1b) of the low-stage compressor (1) (P2) and the pressure of the refrigerant advancing in the suction pipe (5) become lower in this order. Therefore, the relationship among the pressures (P1) (P2) (P3) (P4) is P4>P3>P2> P1 as shown in the following equations.

The refrigerant pressure (P5) at the outlet side of the intercooler (13) is discharged from the discharge port (1b) of the low-stage compressor (1) because the on-off valve (18) is opened. Equal to the refrigerant pressure (P2) generated, and these respective pressures (P2) (P5)
Is lower than the refrigerant pressure (P3) at the connection portion of the second intermediate pressure gas pipe (16) to the high-pressure stage compressor (3), and thus the pressures (P2) (P3) (P5). ), P3> P2 = P5 as shown in the following equation.

As described above, since the refrigerant outlet side of the check valve (19) has a higher pressure than the inlet side thereof, the check valve (19)
Is automatically closed.

Therefore, as shown by the arrow (a) in the figure, the intermediate pressure gas refrigerant evaporated in the intermediate cooler (13) is in the open state of the open / close valve (18) → the first intermediate pressure gas pipe ( 16) → It is supplied to the inlet section (3a) of the high-stage compressor (3) via the connecting pipe (6).

Further, when performing the single-stage compression operation using only the high-pressure stage compressor (3), the on-off valve (18) is closed. At this time, the check valve (19) is temporarily operated. When the closing operation is being performed, the closing operation of the on-off valve (18) causes
Since the refrigerant from the intercooler (11) flows into the check valve (19) side via the second intermediate pressure gas pipe (16), the refrigerant inflow side of the check valve (19). Pressure at (P
5) becomes higher than the pressure (P3) on the outflow side, and P5> P3.

Therefore, as shown by the arrow (b) in the figure, the gas refrigerant evaporated in the intercooler (13) is changed to the second intermediate pressure gas pipe (17) → check valve (19) → high-stage side compression. It is supplied by the route of the machine (3).

Incidentally, during the two-stage compression operation using each of the compressors (1) and (3) as described above, similar to the one shown in FIG. 2, the second reverse pipe inserted in the bypass pipe (7). The stop valve (9b) is closed and the check valve (19) interposed in the suction pipe (5) is opened, so that the suction pipe (9) is opened as shown by the solid line arrow in FIG. Refrigerant from 5) is admitted through the route of the first check valve (9a) → low-stage side compressor (1) → connecting pipe (6) → high-stage side compressor (3), and these high and low The two-stage compression of the refrigerant is performed by both the stage side compressors (1) and (3).

When the single-stage compression operation is performed by driving only the high-pressure stage compressor (3), the first check valve (9a) is opened and the second check valve (9b) is opened. Is closed, and the refrigerant in the suction pipe (5) is cooled by the second check valve (9b) → bypass pipe (7) → communication pipe (6) → higher stage side as shown by the dotted arrow in FIG. By advancing in the path of the compressor (3), the single-stage compression of the refrigerant is performed only by the high-stage side compressor (3).

(Effect of the Invention) As described above, in the two-shaft two-stage refrigeration system of the present invention,
High and low stage compressors (1) on the outlet side of the intercooler (13)
The first intermediate pressure gas pipe (16) reaching the intermediate part of (3) and the second intermediate pressure gas pipe (17) reaching the intermediate part of the high-stage compressor (3) are connected to each other, and 1 Intermediate pressure gas pipe (1
The check valve (19) is provided in the second intermediate pressure gas pipe (17) while allowing the on-off valve (18) to be interposed in the valve 6). Therefore, the structure can be simplified and the cost can be reduced as compared with the case where electromagnetic valves are respectively provided in the intermediate pressure gas pipes (16, 17).

[Brief description of drawings]

FIG. 1 is a piping diagram showing a two-shaft two-stage refrigeration system of the present invention, second
The drawing is a piping diagram for explaining the process leading to the present invention. (1) …… Low-stage compressor (1a) …… Suction port (1b) …… Discharge port (2) …… Drive device (3) …… High-stage compressor (3a) …… Suction port (4) ) …… Drive device (5) …… Suction pipe (6) …… Communication pipe (13) …… Intercooler (16) …… First intermediate pressure gas pipe (17) …… Second intermediate pressure gas pipe ( 18) …… Open / close valve (19) …… Check valve

Claims (1)

[Scope of utility model registration request] 1. A low-stage compressor (1) having a drive (2) and a high-stage compressor (3) having a drive (4).
And a suction pipe (5) is connected to the suction port (1a) of the low-stage compressor (1), and the discharge port (1b) of the low-stage compressor (1) is compressed to the high-stage side. The communication pipe (6) is connected to the suction port (3a) of the machine (3) by a communication pipe (6), and the communication pipe (6) is provided on the outlet side of the intercooler (13).
A two-shaft two-stage refrigeration system in which a first intermediate-pressure gas pipe (16) connected to and a second intermediate-pressure gas pipe (17) connected to an intermediate portion of the high-stage compressor (3) are connected, An opening / closing valve (18) is provided in the first intermediate pressure gas pipe (16), and only the flow to the intermediate portion of the high-stage compressor (3) is allowed in the second intermediate pressure gas pipe (17). A two-shaft two-stage refrigeration system provided with a check valve (19).