CN113758035A

CN113758035A - Refrigerating system

Info

Publication number: CN113758035A
Application number: CN202111097440.XA
Authority: CN
Inventors: 高斌; 高强
Original assignee: Guangdong Meizhi Compressor Co Ltd; Guangdong Meizhi Precision Manufacturing Co Ltd
Current assignee: Guangdong Meizhi Compressor Co Ltd; Guangdong Meizhi Precision Manufacturing Co Ltd
Priority date: 2021-09-18
Filing date: 2021-09-18
Publication date: 2021-12-07
Also published as: WO2023040210A1

Abstract

The invention discloses a refrigerating system, which comprises a compressor assembly, a high-pressure pipeline and a low-pressure pipeline, wherein the compressor assembly comprises a plurality of compressors connected in parallel, the high-pressure pipeline is connected with the exhaust end of the compressor assembly, a first heat exchanger is arranged in the high-pressure pipeline, the low-pressure pipeline is connected with the air inlet end of the compressor assembly, a second heat exchanger is arranged in the low-pressure pipeline, and a throttling part is arranged between the low-pressure pipeline and the high-pressure pipeline; wherein, at least one compressor is first compressor, and first compressor has first intake pipe and first exhaust pipe, and at least one in first intake pipe and the first exhaust pipe is provided with first control valve to through first relief valve intercommunication between first intake pipe and the first exhaust pipe. When the load of the refrigerating system is low, the first compressor is stopped, and the energy consumption is reduced. The pressure difference between the first air inlet pipe and the first exhaust pipe can be rapidly eliminated through the first pressure relief valve, the condition that the first compressor is restarted is met, and the first compressor is prevented from being restarted and failing.

Description

Refrigerating system

Technical Field

The invention relates to the technical field of refrigeration, in particular to a refrigeration system.

Background

In the related art, because the rotary compressor has many advantages of small volume, low cost, high reliability and the like, a refrigeration system adopts a mode that a plurality of rotary compressors work in parallel to meet the requirement of refrigeration capacity. The refrigeration system is characterized in that the refrigeration system is operated by a plurality of rotary compressors at full load at the initial starting stage so as to quickly reach the set temperature condition, when the system is stably operated, part of the rotary compressors can be operated to meet the requirement, and the part of the rotary compressors can be controlled to be stopped so as to save energy, so that the refrigeration system has better economical efficiency, and when the load is increased, the stopped rotary compressors are restarted. The rotary compressor requires the pressure on the suction side and the exhaust side to reach a balanced state during starting due to the design characteristics, and the starting reliability can be ensured only when the set pressure difference is less than 0.1 MPa. However, the high-pressure pipeline and the low-pressure pipeline of the refrigeration system still have large pressure difference, which easily causes the restart failure of the rotary compressor, and the repeated restart failure can cause the rapid temperature rise of the motor, even has the risk of burning the motor.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a refrigerating system which can meet the restarting condition of a rotary compressor and avoid the risk of restarting failure.

The refrigeration system comprises a compressor assembly, a high-pressure pipeline and a low-pressure pipeline, wherein the compressor assembly comprises a plurality of compressors connected in parallel, the high-pressure pipeline is connected with the exhaust end of the compressor assembly, a first heat exchanger is arranged in the high-pressure pipeline, the low-pressure pipeline is connected with the air inlet end of the compressor assembly, a second heat exchanger is arranged in the low-pressure pipeline, and a throttling part is arranged between the low-pressure pipeline and the high-pressure pipeline; wherein, at least one the compressor is first compressor, first compressor has first intake pipe and first exhaust pipe, first intake pipe with at least one in the first exhaust pipe is provided with first control valve, and first intake pipe with communicate through first relief valve between the first exhaust pipe.

The refrigeration system provided by the embodiment of the invention has at least the following beneficial effects: when the load of the refrigerating system is low, the first compressor is stopped, and the energy consumption is reduced. Because at least one in the first intake pipe of first compressor and the first blast pipe sets up first control valve, utilize first control valve can break off first compressor and high-pressure line and/or low-pressure line, and can eliminate the pressure differential between first intake pipe and the first blast pipe fast through first relief valve, satisfy the condition that first compressor restarts, prevent that first compressor from restarting the failure, the risk that the motor that has eliminated first compressor and has restarted the failure and lead to rapid heating up even the motor burns out is improved refrigerating system's operating stability.

According to some embodiments of the invention, the first pressure relief valve has an inlet M communicating with the first exhaust pipe through a pipe and an outlet N communicating with the first intake pipe through a pipe.

According to some embodiments of the invention, the first pressure relief valve has an inlet M and an outlet N, the first pressure relief valve being disposed inside the first compressor, the inlet M communicating with the first exhaust pipe, and the outlet N communicating with the first intake pipe.

According to some embodiments of the invention, the opening pressure difference of the first pressure relief valve is Pr, and Pr is less than or equal to 0.8 MPa.

According to some embodiments of the invention, the first pressure relief valve is electrically connected to a controller, the controller is electrically connected to the first compressor, and the controller controls opening and closing of the first pressure relief valve.

According to some embodiments of the invention, a plurality of the compressors are the first compressor.

According to some embodiments of the invention, the first control valve is a check valve.

According to some embodiments of the invention, the first control valve is an electromagnetic shut-off valve.

According to some embodiments of the invention, the first intake pipe is provided with the first control valve, and the first exhaust pipe is provided with the first control valve.

According to some embodiments of the present invention, an accumulator is connected to the first compressor, the first air inlet pipe is disposed at an inlet of the accumulator, the first control valve disposed on the first air inlet pipe is located in the accumulator, and the first control valve disposed on the first exhaust pipe is located inside the first compressor.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

Additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram of a refrigeration system according to some embodiments of the present invention;

FIG. 2 is a schematic diagram of a first compressor in the refrigeration system of FIG. 1;

FIG. 3 is a cross-sectional view of a first pressure relief valve in some embodiments of the invention;

FIG. 4 is a schematic diagram of a refrigeration system according to further embodiments of the present invention;

FIG. 5 is a schematic diagram of a refrigeration system according to further embodiments of the present invention;

FIG. 6 is a schematic diagram of a first compressor of the refrigeration system of FIG. 5;

FIG. 7 is an enlarged view of a portion of FIG. 6 at G;

FIG. 8 is a cross-sectional view of a check valve in accordance with certain embodiments of the present invention;

FIG. 9 is a schematic diagram of a refrigeration system according to further embodiments of the present invention;

FIG. 10 is a schematic diagram of a refrigeration system according to further embodiments of the present invention;

fig. 11 is a schematic view of a first compressor in the refrigeration system of fig. 10.

The reference numbers are as follows:

the system comprises a first compressor 100, a first air inlet pipe 110, a first exhaust pipe 120, a first control valve 130, a shell 131, a first pressure relief valve 140, a valve body 141 and a liquid storage device 150;

a high pressure line 200, a first heat exchanger 210;

low pressure line 300, second heat exchanger 310;

the throttling part 400.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, if there are first and second described only for the purpose of distinguishing technical features, it is not understood that relative importance is indicated or implied or that the number of indicated technical features or the precedence of the indicated technical features is implicitly indicated or implied.

In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.

The rotary compressor is a compressor widely applied to refrigeration equipment at present, and a motor of the rotary compressor directly drives a rotary piston to rotate to complete compression of a refrigerant without converting the rotary motion of a rotor into reciprocating motion of the piston. The rotary compressor is more suitable for small-sized air conditioners, and is widely applied to household air conditioners in particular.

The main advantages of the rotary compressor are: because the piston rotates, the compression work is smooth, stable and balanced. In addition, the rotary air compressor has no clearance volume and no interference of re-expansion gas, so that the rotary air compressor has the advantages of high compression efficiency, few parts, small volume, light weight, good balance performance, low noise, complete protection measures, low power consumption and the like. The defect is that the rotary compressor has higher requirements on material quality, processing precision, heat treatment, assembly process and lubricating system. With the progress of the technology, the rotary compressor has obvious advantages compared with other types of air compressors, is generally applied to household air conditioners, refrigerators and other electrical appliances, and becomes the leading product in the market from the development trend.

In the related art, a large-scale refrigeration system adopts a mode that a plurality of rotary compressors work in parallel to meet the requirement of large-scale change of refrigeration load. The refrigeration system is characterized in that the refrigeration system is started to run by a plurality of rotary compressors in full load at the initial stage so as to quickly reach the set temperature condition, when the system runs stably, one part of the rotary compressors can run to meet the refrigeration load, and the other part of the rotary compressors can be controlled to stop to save energy, so that the refrigeration system has better economical efficiency. When the load of the refrigeration system increases, the stopped rotary compressor is restarted to provide a sufficient cooling capacity. The rotary compressor requires the pressure on the suction side and the exhaust side to reach a balanced state when starting due to the design characteristics, and the reliability of starting can be ensured when the pressure difference is less than 0.1 MPa. However, the high-pressure pipeline and the low-pressure pipeline of the refrigeration system still have large pressure difference, which easily causes the restart failure of the rotary compressor, and the repeated restart failure can cause the rapid temperature rise of the motor of the rotary compressor, even has the risk of burning the motor, and seriously affects the use.

With reference to fig. 1 to 6, an embodiment of the present invention proposes a refrigeration system comprising a compressor assembly composed of a plurality of compressors connected in parallel, it being understood that the compressors herein are mainly rotary compressors, and can be extended to other types of compressors, balancing the pressures on the intake and discharge sides, being advantageous for all types of compressor start-up. The following description will take as an example a compressor assembly employing a plurality of rotary compressors connected in parallel. In addition, the plurality of rotary compressors of the compressor assembly are all stoppable, the stoppable rotary compressor is defined as the first compressor 100, as shown in fig. 1, the compressor assembly comprises the plurality of first compressors 100 connected in parallel, and in the operation of a refrigeration system, the start and stop of the plurality of first compressors 100 are controlled according to refrigeration load, so that the requirement of refrigeration capacity can be met, the energy consumption can be reduced, and the compressor assembly has better economical efficiency.

The refrigeration system further comprises a high-pressure pipeline 200 and a low-pressure pipeline 300, the exhaust end of the compressor assembly is communicated with the high-pressure pipeline 200, the air inlet end of the compressor assembly is communicated with the low-pressure pipeline 300, namely exhaust of the first compressors 100 connected in parallel is input into the high-pressure pipeline 200, intake air of the first compressors 100 connected in parallel is from the low-pressure pipeline 300, the high-pressure pipeline 200 is provided with a first heat exchanger 210, the low-pressure pipeline 300 is provided with a second heat exchanger 310, and the throttling part 400 is arranged between the low-pressure pipeline 300 and the high-pressure pipeline 200, namely the throttling part 400 is positioned between the first heat exchanger 210 and the second heat exchanger 310. When the refrigerating system operates, the compressor assembly outputs high-temperature and high-pressure refrigerant gas, the high-temperature and high-pressure refrigerant gas is cooled through the first heat exchanger 210, refrigerant liquid is output through the throttling function of the throttling part 400, the refrigerant liquid is evaporated into low-temperature and low-pressure refrigerant gas in the second heat exchanger 310, meanwhile, cold air is produced through the second heat exchanger 310, the requirement for cold energy is met, the low-temperature and low-pressure refrigerant gas is conveyed back to the compressor assembly from the low-pressure pipeline 300, primary circulation of the refrigerant is completed, the refrigerant continuously circulates and operates, and the refrigerating system can continuously provide cold energy.

After the operation of the refrigeration system enters a steady state, the demand for cooling capacity decreases, and a portion of the first compressor 100 is stopped. Referring to fig. 2, a first intake pipe 110 is disposed at an intake end of the first compressor 100, and a first exhaust pipe 120 is disposed at an exhaust end, that is, a plurality of parallel first compressors 100 are all communicated with a low-pressure pipeline 300 through the first intake pipe 110, and are communicated with a high-pressure pipeline 200 through the first exhaust pipe 120, first control valves 130 are disposed on the first intake pipe 110 and the first exhaust pipe 120, when the first compressor 100 is in a shutdown state, the first intake pipe 110 and the low-pressure pipeline 300 can be cut off through the first control valve 130, and the first exhaust pipe 120 and the high-pressure pipeline 200 are cut off at the same time, the first compressor 100 is independent of a pipeline of a refrigeration system, and a first pressure relief valve 140 is disposed between the first intake pipe 110 and the first exhaust pipe 120, and the intake end and the exhaust end of the first compressor 100 can be connected by using the first pressure relief valve 140, so as to eliminate a pressure difference. It will be appreciated that the first pressure relief valve 140 is located between the first control valve 130 in the first inlet line 110 and the first control valve 130 in the first outlet line 120, and is not affected by the high pressure line 200 and the low pressure line 300 when pressure is relieved.

When the load of the refrigeration system is low, part of the first compressors 100 or all of the first compressors 100 are stopped, energy consumption is reduced, the first compressors 100 are isolated by the first control valve 130, and then the pressure difference between the air inlet end and the air outlet end is rapidly eliminated by the first pressure relief valve 140, so that the condition that the first compressors 100 are restarted is met. When the load changes, a part of the first compressors 100 or all the first compressors 100 are restarted, the problem of restart failure of the first compressors 100 is solved, the risk of rapid motor temperature rise and even motor burnout caused by restart failure of the first compressors 100 is eliminated, and the operation stability of the refrigerating system is improved.

It can be understood that the first air inlet pipe 110 is disposed at an air inlet end of the first compressor 100, and the first exhaust pipe 120 is disposed at an air exhaust end, that is, the plurality of parallel first compressors 100 are all communicated with the low pressure pipeline 300 through the first air inlet pipe 110, and are communicated with the high pressure pipeline 200 through the first exhaust pipe 120, and the first air inlet pipe 110 is disposed with the first control valve 130. When the first compressor 100 is in a shutdown state, the first air inlet pipe 110 and the low pressure pipeline 300 can be cut off by the first control valve 130, the first compressor 100 is only communicated with the high pressure pipeline 200, the air inlet end and the air outlet end of the first compressor 100 are communicated by the first pressure relief valve 140, the air inlet end and the air outlet end are both near the pressure of the high pressure pipeline 200, and the pressure difference can be eliminated.

Or, the air inlet end of the first compressor 100 is provided with a first air inlet pipe 110, and the air outlet end is provided with a first air outlet pipe 120, that is, the plurality of parallel first compressors 100 are all communicated with the low-pressure pipeline 300 through the first air inlet pipe 110 and communicated with the high-pressure pipeline 200 through the first air outlet pipe 120, and the first air outlet pipe 120 is provided with a first control valve 130. When the first compressor 100 is in a shutdown state, the first exhaust pipe 120 and the high-pressure pipeline 200 can be cut off by the first control valve 130, the first compressor 100 is only communicated with the low-pressure pipeline 300, the first pressure relief valve 140 is used for conducting the air inlet end and the air outlet end of the first compressor 100, the air inlet end and the air outlet end are both pressure close to the low-pressure pipeline 300, and pressure difference can be eliminated.

It will be appreciated that it is also possible that only some of the compressors of the compression assembly are stoppable, such as one, two. Taking the refrigeration system with one first compressor 100 as an example, the first compressor 100 is communicated with the low pressure pipeline 300 through the first intake pipe 110, and is communicated with the high pressure pipeline 200 through the first exhaust pipe 120, the high pressure pipeline 200 is provided with the first heat exchanger 210, the low pressure pipeline 300 is provided with the second heat exchanger 310, the throttling component 400 is arranged between the low pressure pipeline 300 and the high pressure pipeline 200, that is, the throttling component 400 is arranged between the first heat exchanger 210 and the second heat exchanger 310; first intake pipe 110 and first exhaust pipe 120 are all provided with first control valve 130, first compressor 100 is under the shutdown state, can cut off first intake pipe 110 and low-pressure pipeline 300 through first control valve 130, can cut off first exhaust pipe 120 and high-pressure pipeline 200 through first control valve 130, first compressor 100 is independent of the pipeline of refrigerating system, and be provided with first relief valve 140 between first intake pipe 110 and the first exhaust pipe 120, utilize first relief valve 140 can switch on the inlet end and the exhaust end of first compressor 100, eliminate the pressure differential.

When the load of the refrigeration system is low, only the first compressor 100 is stopped, so that the energy consumption is reduced; when the load changes, first compressor 100 restarts, has solved the problem that first compressor 100 restarts the failure, has eliminated the risk that the motor rapid heating that first compressor 100 restarts the failure and leads to burns out even the motor, improves refrigerating system's operating stability.

It can be understood that, as shown in fig. 3, the first pressure relief valve 140 includes a valve body 141, a through valve cavity is disposed in the valve body 141, a valve plate F and a spring E are disposed in the valve cavity, an inlet M of the first pressure relief valve 140 is communicated with a discharge end of the first compressor 100, an outlet N of the first pressure relief valve is communicated with an intake end of the first compressor 100, the spring E pushes the valve plate F in a normal state, the valve plate F leaves the valve port, and the first pressure relief valve 140 is in an open state. When the first compressor 100 is operated, the differential pressure force of the differential pressure between the inlet M and the outlet N acting on the valve plate F is greater than the elastic force of the spring E, and the valve plate F closes the first pressure relief valve 140. When the first compressor 100 stops, the pressure at the exhaust end and the pressure at the intake end tend to be balanced, the pressure difference between the inlet M and the outlet N decreases, when the pressure difference force of the pressure difference acting on the valve plate F is smaller than the spring force of the spring E, the valve plate F is pushed open by the spring force, the first pressure relief valve 140 is opened, the pressure at the exhaust end and the intake end of the first compressor 100 is quickly relieved through the first pressure relief valve 1407 to reach pressure balance, and the condition that the first compressor 100 is restarted is met.

It can be understood that, the opening pressure difference of the first pressure relief valve 140 is generally defined as Pr, Pr is required to be less than or equal to 0.8Mpa, when the pressure difference between the inlet M and the outlet N is less than or equal to 0.8Mpa, the pressure difference force acting on the valve plate F is less than the spring force of the spring E, the valve plate F is pushed open by the spring force, the first pressure relief valve 140 is opened, and the exhaust end and the intake end of the first compressor 100 are quickly relieved by the first pressure relief valve 1407 to reach pressure balance, so as to meet the condition of restarting the first compressor 100.

Referring to fig. 2, it can be appreciated that the first pressure relief valve 140 may be disposed outside the first compressor 100, an inlet M of the first pressure relief valve 140 communicates with the first exhaust pipe 120 through a pipe between the first control valve 130 and the exhaust end of the first compressor 100, and an outlet N of the first pressure relief valve 140 communicates with the first intake pipe 110 through a pipe between the first control valve 130 and the intake end of the first compressor 100, which is convenient for assembly and has a simple structure.

Referring to fig. 5 to 7, it can be understood that a first pressure relief valve 140 may be further disposed inside the first compressor 100, the first compressor 100 having an accumulator 150, the accumulator 150 being provided on the first intake pipe 110, an inlet M of the first pressure relief valve 140 communicating with the first exhaust pipe 120 through an inner space of the first compressor 100, and an outlet N of the first pressure relief valve 140 directly communicating with a port of the first intake pipe 110 located inside the first compressor 100. The first pressure relief valve 140 is disposed inside the first compressor 100, so that the first compressor 100 is more compact in structure, and the layout of the refrigeration system is facilitated.

Referring to fig. 4, it can be understood that the first pressure relief valve 140 may also be controlled by a controller, the controller is electrically connected to the first compressor 100 at the same time, after the first compressor 100 is stopped, the controller controls the first pressure relief valve 140 to open for pressure relief, and when the first compressor 100 is started, the first pressure relief valve 140 is automatically closed; or the first pressure relief valve 140 is an externally controlled valve, and the opening and closing of the first pressure relief valve 140 are controlled by an external signal, if the first pressure relief valve 140 is controlled by a relay, after the first compressor 100 is stopped, the first pressure relief valve 140 is automatically opened for pressure relief after a set time, and when the first compressor 100 is started, the first pressure relief valve 140 is automatically closed.

Referring to fig. 4 and 8, it can be understood that the first control valve 130 may be a check valve, the check valve includes a housing 131, a power mechanism such as a spring C is disposed in the housing 131 for automatically pushing the valve plate D to close the valve port, and when no refrigerant flows from the inlet a to the outlet B of the check valve, the spring C pushes the valve plate D to close the check valve; when fluid flows from the inlet a to the outlet B of the check valve, the fluid overcomes the spring force of the spring C, opening the check valve. Fig. 8 shows only a common one-way valve structure, and all the one-way valves with an automatic closing function can be applied to the embodiment of the present invention.

Referring to fig. 9, it can be understood that the first control valve 130 may also be an electromagnetic shutoff valve, and after the first compressor 100 is stopped, the electromagnetic shutoff valve is automatically closed to isolate the first compressor 100, so as to prevent the pressure difference between the high-pressure pipeline 200 and the low-pressure pipeline 300 from affecting the restart of the first compressor 100; the first compressor 100 is restarted and the electromagnetic cut-off valve is automatically opened.

Referring to fig. 10 and 11, it can be understood that an electromagnetic cut-off valve may also be disposed inside the first compressor 100, both the electromagnetic cut-off valve and the first pressure relief valve 140 being located inside the first compressor 100. The electromagnetic shutoff valve connected to the first intake pipe 110 is disposed inside the liquid storage 150, and the electromagnetic shutoff valve connected to the first exhaust pipe 120 is disposed inside the first compressor 100, so that the first compressor 100 is more compact in structure, and the layout of the refrigeration system is facilitated.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

Claims

1. A refrigeration system, comprising:

a compressor assembly comprising a plurality of compressors in parallel;

the high-pressure pipeline is connected with the exhaust end of the compressor assembly, and a first heat exchanger is arranged in the high-pressure pipeline;

the low-pressure pipeline is connected with the air inlet end of the compressor assembly, a second heat exchanger is arranged in the low-pressure pipeline, and a throttling part is arranged between the low-pressure pipeline and the high-pressure pipeline;

wherein, at least one the compressor is first compressor, first compressor has first intake pipe and first exhaust pipe, first intake pipe with at least one in the first exhaust pipe is provided with first control valve, and first intake pipe with communicate through first relief valve between the first exhaust pipe.

2. The refrigeration system of claim 1 wherein the first pressure relief valve has an inlet in communication with the first exhaust conduit via a conduit and an outlet in communication with the first intake conduit via a conduit.

3. The refrigeration system of claim 1, wherein the first pressure relief valve has an inlet and an outlet, the first pressure relief valve being disposed within the first compressor, the inlet being in communication with the first exhaust conduit, and the outlet being in communication with the first intake conduit.

4. The refrigeration system according to claim 2 or 3, wherein the opening pressure difference of the first pressure relief valve is set to Pr so as to satisfy Pr ≦ 0.8 MPa.

5. The refrigeration system according to claim 2 or 3, wherein the first pressure relief valve is electrically connected to a controller, the controller is electrically connected to the first compressor, and the controller controls opening and closing of the first pressure relief valve.

6. The refrigerant system as set forth in claim 1, wherein a plurality of said compressors are each said first compressor.

7. The refrigerant system as set forth in claim 1, wherein said first control valve is a check valve.

8. The refrigerant system as set forth in claim 1, wherein said first control valve is a solenoid shut-off valve.

9. A refrigeration system as set forth in claim 7 or 8 wherein said first intake conduit is provided with said first control valve and said first exhaust conduit is provided with said first control valve.

10. The refrigeration system as recited in claim 9 wherein an accumulator is connected to said first compressor, said first intake pipe is disposed at an inlet of said accumulator, said first control valve disposed on said first intake pipe is located in said accumulator, and said first control valve disposed on said first exhaust pipe is located inside said first compressor.