JPH049553A - Cryogenic freezer and its operating method - Google Patents

Abstract

PURPOSE:To enable a high freezing capability to be outputted within a lower temperature range by a method wherein when a freezer is started to operate, a discharging pressure of a compressor is restricted low, an over-load operation of the compressor is prevented, a refrigerant condensing state is promoted and even after a pressure in the freezer is reduced, a sufficient amount of refrigerant is circulated. CONSTITUTION:When an operation is started, the first opening or closing valve 15 and the second opening or closing valve 16 are opened, a bypass flow passage for refrigerant is generated and in concurrent with this operation, the first tank 13 and the second tank 14 are kept under a discharging pressure, the refrigerant is stored to restrict the discharging pressure of the compressor low. Then, the second opening or closing valve 16 is closed, the bypassing flow of the refrigerant is stopped and then the first opening or closing valve 15 is closed and the second opening or closing valve 16 is opened. The refrigerant in the second tank 14 passes through a flow rate metering mechanism 17 in reference to a pressure difference between a discharging pressure and a suction pressure, gradually moves to a compressor suction side refrigerant pipe 12 and the refrigerant is circulated to the heat exchanger system by the compressor 1. At this time, in order to prevent a compressor discharging pressure from being rapidly increased, the first tank 13 is operated as a pressure damping tank.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low temperature refrigerator using a compressor, and more particularly to a refrigerator for obtaining a low temperature using a plurality of types of non-azeotropic mixed refrigerants. .

[Conventional technology]

In a known single-stage refrigeration system, refrigerant vapor is compressed by a compressor, this compressed refrigerant is condensed by exchanging heat with air or cooling water, and this condensate is adjusted to a low pressure by an expansion valve to undergo adiabatic expansion. This generates a refrigeration effect and eventually returns to the compressor. Furthermore, in the known multi-component cascade cycle, a desired low temperature can be obtained by using a single component refrigerant and combining refrigeration cycles in multiple stages. On the other hand, in a mixed refrigeration cycle, a low temperature can be obtained by liquefying and separating a mixed refrigerant stepwise in the order of high boiling points, sequentially condensing a low-point refrigerant, and adiabatically expanding the refrigerant.

The above mixed refrigerant refrigeration cycle will be explained using FIG. 3, which is a conventional basic circuit diagram. In FIG. 3, a mixed refrigerant is adiabatically compressed by a compressor 1, and this adiabatic refrigerant is cooled by cooling water or the like in a condenser 2 and partially condensed.
The first separator 4 separates the refrigerant into condensed refrigerant and uncondensed refrigerant.

The separated condensed refrigerant is adiabatically expanded in the first decompressor 9 to generate a low temperature, is combined with the refrigerant returned from the low temperature section, is passed through the first heat exchanger 6, and is passed through the first separator 4. The separated uncondensed refrigerant is further cooled and partially condensed. By repeating this process one after another, refrigerants with lower boiling points are condensed and adiabatically expanded, thereby generating refrigerant gas at a lower temperature.

[Problem to be solved by the invention]

In the mixed refrigerant refrigeration system as described above, there is a large difference between the pressure in each part of the refrigerator when the refrigerator is started and the pressure in each part of the refrigerator in a steady state.

In the steady state, each low temperature section is maintained at a predetermined low temperature state, and the refrigerant is partially condensed, so the pressure inside the machine is kept low. On the other hand, at startup, the refrigerant temperature is close to room temperature and the amount of condensation is small, so the compressor discharge pressure in particular becomes extremely high. For this reason, a heavy load is placed on the compressor, and the operation of the compressor may have to be stopped. Conversely, if the compressor discharge pressure at startup is kept low, the internal pressure will drop as the refrigeration cycle progresses, making it impossible to condense the desired refrigerant.

In order to obtain refrigerant at a lower temperature, it is necessary to keep the compressor discharge pressure low at startup and maintain a predetermined discharge pressure during steady state.

A conventional method for solving this problem will be explained using FIG. 4. In addition, in Fig. 4 and the above-mentioned Fig. 3,
Identical equipment is indicated by the same number.

In FIG. 4, the basic mixed refrigerant refrigeration cycle is as described above using FIG. 3. Bypass piping 20 that communicates refrigerant discharge piping 3 and refrigerant suction piping 12
A flow rate regulating valve 18 or a pressure regulating valve (not shown) is attached to this bypass piping. Flow! The regulating valve 18 operates according to the discharge pressure of the compressor, adjusts the flow rate of refrigerant in the bypass pipe 20, and operates so that the discharge pressure of the compressor does not exceed a set value.

In this device, the discharge pressure of the compressor or the amount of refrigerant circulation changes rapidly due to the operation of the flow rate adjustment valve 18.
The gas-liquid separation function of the first gas-liquid separator 4 may not function properly. In this case, the liquid refrigerant and machine oil flow into the first heat exchanger 6 together with the gas refrigerant, are cooled, and enter the second gas-liquid separator 5. The liquid refrigerant and machine oil to be separated in the first gas-liquid separator are transferred to the second pressure reducer 10 or the second heat exchanger 7.
It had the disadvantage that it would freeze in the return flow path, causing an M blockage accident.

SUMMARY OF THE INVENTION Therefore, the present invention provides a refrigerating machine and a method for operating the same, which do not have the above-mentioned drawbacks and can suppress the pressure rise inside the machine to a low level during startup and maintain a predetermined pressure inside the machine during steady operation using simple means. The purpose is to provide

[Means to solve the problem]

The present invention uses a refrigerant tank, an on-off valve, and a refrigerant flow rate restricting mechanism to keep the discharge pressure of the compressor low when starting the refrigerator, thereby preventing overload operation of the compressor, and when refrigerant condensation progresses. By circulating a sufficient amount of refrigerant even after the pressure inside the machine has decreased, it is possible to achieve greater refrigerating capacity at lower temperatures.

That is, the present invention includes a compressor, a condenser, an evaporator, a plurality of heat exchangers through which refrigerant sent from the compressor discharge side and a return refrigerant from the evaporator flow, and a plurality of separators and a pressure reducer. It uses multiple non-azeotropic mixed refrigerants as refrigerants,
The condensed refrigerant that has passed through the separator is passed through the pressure reducer and combined with the refrigerant returned from the evaporator in the heat exchanger, the uncondensed refrigerant in the refrigerant is cooled, and the refrigerant with a lower boiling point is sequentially condensed. In a refrigerator that obtains a low temperature by means for causing refrigerant to flow to the evaporator via a final stage or intermediate pressure reducer, from the refrigerant discharge piping on the discharge side of the compressor,
A bypass passage communicating with the refrigerant suction pipe on the compressor suction side is provided, and the bypass passage includes a first tank, a first on-off valve, a second tank, a second on-off valve, and a flow rate restrictor from the refrigerant discharge pipe side. This refrigerator is characterized by having a streamer mechanism arranged in series.

In addition, in this refrigerator, the first on-off valve and the second on-off valve are opened during startup, and after a predetermined period of time has elapsed, the first on-off valve and the second on-off valve are opened.
The method of operating a refrigerator is characterized in that the second on-off valve is closed, then the first on-off valve is closed, and then the second on-off valve is opened.

According to the present invention, the compressor discharge pressure at startup is kept low,
In addition, a predetermined discharge pressure can be maintained during steady state, and the desired low-temperature refrigerant can be obtained without any problems.

[Effect]

A bypass pipe is provided to communicate the compressor discharge side refrigerant pipe and the compressor suction side refrigerant pipe, and in the middle thereof, from the discharge side, a first tank, a first on-off valve, a second tank, a second on-off valve, and a refrigerant flow restrictor are installed. Deploy mechanisms in series. At startup, both the first on-off valve and the second on-off valve are opened to bypass the refrigerant. Further, due to the refrigerant flow rate restricting mechanism, the internal pressures of the first tank and the second tank become approximately the same pressure as the discharge pressure, and a predetermined amount of refrigerant is stored. After a while after startup, the refrigerant gradually condenses and the pressure inside the refrigerator begins to decrease. Therefore, first, the second on-off valve installed on the downstream side of the bypass circuit is closed.

As a result, the entire amount of the refrigerant discharged from the compressor circulates within the heat exchanger without passing through the bypass circuit.

Due to the buffering effects of the first tank and the second tank, the discharge pressure increase and pressure vibration of the compressor due to this are hardly caused.

Next, the first on-off valve located between the first tank and the second tank is closed to seal off the refrigerant in the second tank. after that,
The second on-off valve is opened and the refrigerant stored in the second tank is transferred to the circulation system through the refrigerant flow restricting mechanism.

In the above operation, neither a sudden upward change nor a pulsating change occurs in the change in the discharge pressure of the compressor, and the function of the gas-liquid separator can always function normally.

〔Example〕

The present invention will be explained below using examples. However, the present invention is not limited to this example.

Embodiment 1 FIG. 1 is a route diagram showing an embodiment of the present invention. In FIG. 1, a mixed refrigerant is adiabatically compressed by a compressor 1, this compressed refrigerant is cooled with cooling water etc. in a condenser 2, and partially condensed, and this gas-liquid mixed refrigerant is transferred to a first separator 4. The refrigerant is separated into mixed refrigerant and uncondensed refrigerant. The separated condensed refrigerant is adiabatically expanded in the first pressure reducer 9 to generate a low temperature, is combined with the refrigerant returned from the low temperature section, is passed through the first heat exchanger 6, and is separated in the first separator. The uncondensed refrigerant is further cooled and partially condensed. By repeating this in sequence, refrigerants with lower boiling points are successively condensed, and the condensed refrigerant is adiabatically expanded, thereby generating refrigerant gas at a lower temperature.

In addition, the intake side refrigerant pipe 12 is connected to the compressor discharge side refrigerant pipe 3.
A first tank 13, a first on-off valve 15,
A second tank 14, a second on-off valve 16, and a flow rate restricting mechanism 17 are provided. At the time of startup, the first on-off valve 15 and the second on-off valve 16 are opened to create a bypass flow path for the refrigerant, while at the same time keeping the first tank 13 and the second tank 4 at the discharge side pressure to store the refrigerant. This keeps the compressor discharge pressure low.

Next, the second shut-off valve 16 is closed to stop the bypass flow of the refrigerant, and then the first shut-off valve 15 is closed, and then the second shut-off valve 16 is opened. Due to the pressure difference between the discharge pressure and the suction pressure, the refrigerant in the second tank 14 is gently transferred to the compressor suction side refrigerant pipe 12 through the flow rate restricting mechanism 17, and is circulated to the heat exchanger system by the compressor 1. . At this time, in order to prevent the compressor discharge pressure from increasing rapidly, the first tank 13 is made to function as a pressure buffer tank.

As described above, the temporal fluctuations of the on-off valve and tank internal pressure are
It is as shown in FIG. 2 in a simplified manner.

〔Effect of the invention〕

According to the present invention, it is possible to suppress the temporary compressor discharge pressure at startup to a low level, to perform a good compressor startup, and to ensure the amount of refrigerant circulation even in a steady state, and to maintain sufficient refrigeration capacity. It is possible to drive to the best of your ability.

Further, rapid pressure fluctuations can be prevented and the operation of the gas-liquid separator can be maintained normally at all times.

[Brief explanation of the drawing]

FIG. 1 is a route diagram showing an example of the refrigerator of the present invention,
Figure 2 is a diagram showing the opening/closing valve operation and tank internal pressure changes of the refrigerator shown in Figure 1, and Figure 3 is a path diagram of the most basic refrigerator using a non-azeotropic mixed refrigerant. FIG. 4 is a route diagram showing an example of a conventional refrigerator in which the compressor discharge pressure at startup is kept low. 1 Compressor, 2! ! Compressor, 3 Discharge side refrigerant piping, 4
1st gas-liquid separator, 5 2nd gas-liquid separator, 6 1st heat exchanger, 7 2nd heat exchanger, 8 evaporator 9 1st pressure reducer,
10 Second pressure reducer, 11 Third pressure reducer, 12 Intake side refrigerant piping, 13 First tank, 14 Second tank, 15 First on-off valve, 16 Second on-off valve, 17 Flow rate throttling mechanism, 1
8. Flow rate adjustment valve, 19. Pressure detector Patent applicant: Ebara Corporation Representative: Keito Yoshimine
Matsu 1) Large → If question

Claims (1)

[Claims] 1. A compressor, a condenser, an evaporator, a plurality of heat exchangers through which the refrigerant sent from the compressor discharge side and the refrigerant returned from the evaporator flow, and a plurality of separators and pressure reduction. A plurality of non-azeotropic mixed refrigerants are used as the refrigerant, and the refrigerant condensed from the refrigerant that has passed through the separator is transferred to the heat exchanger via the pressure reducer and the refrigerant returned from the evaporator. means for merging the refrigerant, cooling the uncondensed refrigerant in the refrigerant, and sequentially condensing the refrigerant with a lower boiling point;
In a refrigerator that obtains a low temperature by circulating refrigerant to the evaporator via a final stage or intermediate pressure reducer, the refrigerant discharge pipe on the compressor discharge side communicates with the refrigerant suction pipe on the compressor suction side. A bypass passage is provided, and a first tank, a first on-off valve, a second tank, a second on-off valve, and a flow rate restricting mechanism are arranged in series in the bypass passage from the refrigerant discharge piping side. refrigerator. 2. In the refrigerator according to claim 1, the first
Operate with the on-off valve and the second on-off valve opened, and after a predetermined period of time, first close the second on-off valve, then close the first on-off valve, and then open the second on-off valve. The method for operating a refrigerator, characterized in that: