JPH10292948A - Refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool a closed type electric motor efficiently without decreasing the efficiency in a refrigerator equipped with a multistage compressor that is driven by the closed type electric motor cooled by a refrigerant. SOLUTION: The first intermediate cooler 35 is provided to cool the liquid refrigerant condensed by a condenser 6 by decompressing it to the first intermediate pressure, and then the gas refrigerant which is evaporated by this first intermediate cooler 35 is returned to the intermediate stage of a multistage compressor 1 through an intermediate suction pipe 11 and an intermediate suction valve 8 interposed therein, so that the total amount of the liquid refrigerant cooled by this first intermediate cooler 35 is supplied to a stator 3 of the closed type electric motor 2 to cool it. The second intermediate cooler 38 is provided to decompress the liquid refrigerant after cooling the stator 3 to the second intermediate pressure to cool the liquid refrigerant. The liquid refrigerant which is cooled by this second intermediate cooler 38 is supplied to an evaporator 5, and the total amount of the gas refrigerant which is evaporated by this second intermediate cooler 38 is supplied to a rotor 4 of the closed type electric motor 2 to cool the rotor. The gas refrigerant after cooling the rotor 4 is returned to the suction pipe 9 of the back stream side of the evaporator 5 through the return pipe 19 and an automatic valve 20 interposed therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a refrigerator.

[0002]

2. Description of the Related Art An example of a conventional refrigerator is shown in FIG. When the refrigerator is operated, the high-pressure gas refrigerant discharged from the multi-stage compressor 1 enters the condenser 6 via the discharge pipe 10 and radiates heat to a cooling medium such as cooling water flowing through the heat transfer pipe 18. To condense and liquefy.

The liquid refrigerant is extracted from the liquid reservoir 14 and enters the intercooler 7, where it is throttled to an intermediate pressure by the high-pressure side throttle mechanism 24. After being separated, the high-stage side impeller of the multi-stage compressor 1 passes through the intermediate suction pipe 11 and the intermediate suction valve 8 interposed therebetween.
Inspired by 28. After the remaining liquid refrigerant is cooled by the latent heat of evaporation, the flow rate is adjusted by being throttled by the low-pressure side throttle mechanism 25, and at the same time, adiabatically expands to a low-pressure gas-liquid two-phase flow.

[0004] This refrigerant enters the evaporator 5, where the heat transfer tube
16Brine flowing through the inside, heat is absorbed from the medium to be cooled such as cold water, and evaporates and evaporates to become a low-pressure gas refrigerant,
It is sucked into the multi-stage compressor 1 through the suction pipe 9 and compressed by the low-stage impeller 27 and the high-stage impeller 28 through the inlet vane 15.

[0005] The impellers 27 and 28 of the multi-stage compressor 1 have a rotating shaft 29.
And housed inside the sealed housing 30. The rotating shaft 29 is fixed to an output shaft 33 of the electric motor 2 via gears 31 and 32, and the rotor 4 and the stator 3 of the electric motor 2 are housed in a closed casing 34.

The liquid refrigerant extracted from the liquid reservoir 14 of the condenser 6 is supplied to the outer periphery of the stator 3 of the electric motor 2 through the supply pipe 12 to cool the outer peripheral surface. Next, a part of the liquid refrigerant passes through a passage from the outer peripheral surface of the stator 3 to the inner peripheral surface, flows into a gap between the inner peripheral surface of the stator 3 and the outer peripheral surface of the rotor 4, and evaporates in a process of cooling these. After that, it is sucked into the evaporator 5 through the return pipe 13.

A Mollier diagram of the refrigeration cycle is shown in FIG. The refrigerant gas is changed from A to B by being compressed by the low-stage impeller 27 of the turbo compressor 1,
In the state described above, the air is sucked into the high-stage impeller 28 and compressed, whereby the state becomes D.

[0008] The gas refrigerant is cooled by the condenser 6 to the state of E, and then condensed to form F
Saturated liquid refrigerant. This saturated liquid refrigerant is throttled by the high-pressure side throttle mechanism 24 of the intercooler 7 to
State. Then, a part thereof evaporates to an H state, and then the pressure is reduced by the intermediate suction valve 8 to become an I state, and is sucked into the high stage impeller 28 in a C state.

The remaining liquid refrigerant is cooled to be in the state of J, and is throttled by the low-pressure side throttle mechanism 25 to be in the state of K. The refrigerant evaporates in the evaporator 5 to be in the state of L in the multistage compressor 1 and is decompressed by the inlet vane 15 to the state of A.

The liquid refrigerant extracted from the liquid reservoir 14 of the condenser 6 is cooled to the electric motor 2 to enter the state of M through a system shown by a broken line and is sucked into the evaporator 5. Note that N is a saturated liquid line, and O is a saturated vapor line.

[0011]

In the above-described conventional refrigerator, the liquid refrigerant evaporates in the gap between the inner peripheral surface of the stator 3 and the outer peripheral surface of the rotor 4 to form a gas-liquid two-phase.
Has a problem that the rotational resistance of the motor 2 increases and the mechanical loss of the electric motor 2 increases.

Further, since a large amount of liquid refrigerant is required to cool the electric motor 2, there is a problem that the efficiency of the refrigerator is deteriorated. Further, the pressure of the liquid refrigerant supplied to the electric motor 2 changes depending on the temperature of the cooling medium flowing through the heat transfer tube 18 of the condenser 6 and the temperature of the cooling medium flowing through the heat transfer tube 16 of the evaporator 5. Therefore, the amount of refrigerant required for cooling the electric motor 2 may not be secured.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is to provide a multi-stage compressor driven by a hermetic motor cooled by a refrigerant. , A condenser including a condenser and an evaporator, a first intermediate cooler for cooling the liquid refrigerant condensed by the condenser by reducing the liquid refrigerant to a first intermediate pressure. The gas refrigerant evaporated by the cooler is returned to the intermediate stage of the multi-stage compressor through the intermediate suction pipe, and the liquid refrigerant cooled by the first intermediate cooler is supplied to the stator of the hermetic motor to cool it. A second intermediate cooler for cooling the liquid refrigerant after cooling the stator by reducing the liquid refrigerant to a second intermediate pressure lower than the first intermediate pressure is provided, and the second intermediate cooler cools the liquid refrigerant. The evaporator The gas refrigerant evaporated in the second intercooler supplies in the refrigerator, characterized by cooling the supplied to the rotor of the sealed motor.

Another feature is that the intermediate suction pipe is provided with an intermediate suction valve for maintaining a differential pressure between the suction pressure of the multi-stage compressor and the intermediate suction pressure at a certain level or more, and the sealed motor is provided with An automatic valve for maintaining the temperature of the gas refrigerant below a certain value is provided in a return pipe for returning the gas refrigerant after cooling the rotor to the downstream side of the evaporator.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is shown in FIG. The liquid refrigerant condensed in the condenser 6 enters the first intermediate cooler 35 from the liquid reservoir 14 and is reduced to the first intermediate pressure by being throttled by the throttle mechanism 36. As a result, a part of the liquid refrigerant evaporates, and the remaining liquid refrigerant is cooled by the latent heat of evaporation.

This gas refrigerant separates the mist of the liquid refrigerant contained therein in the process of flowing through the eliminator 37,
It is sucked into the intermediate stage of the multi-stage compressor 1 via the intermediate suction pipe 11 and the intermediate suction valve 8 interposed therebetween. By controlling the intermediate suction valve 8 simultaneously with the inlet vane 15, the differential pressure between the suction pressure of the multi-stage compressor 1 and the intermediate suction pressure is maintained at a certain level or more.

The liquid refrigerant cooled by the first intercooler 35 enters a chamber 42 formed by partitioning the inside of the casing 34 of the closed electric motor 2 and cools the stator 3 housed therein.

The liquid refrigerant that has cooled the stator 3 enters a second intermediate cooler 38, and is reduced by a throttle mechanism 39 to a second intermediate pressure lower than the first intermediate pressure. As a result, a part of the liquid refrigerant evaporates, and the remaining liquid refrigerant is cooled by the latent heat of evaporation.

This gas refrigerant separates the mist of the liquid refrigerant contained therein in the process of flowing through the eliminator 40,
It enters a chamber 43 formed in a casing 34 of the hermetic motor 2 and cools the rotor 4 housed therein.

The gas refrigerant that has cooled the rotor 4 enters the suction pipe 9 on the downstream side of the evaporator 5 via the return pipe 19 and the automatic valve 20 interposed therebetween. The automatic valve 20 is controlled by a command from a temperature sensor 44 for detecting the temperature of the gas refrigerant after cooling the rotor 4, and maintains the temperature of the gas refrigerant at a certain value or less.

The liquid refrigerant cooled by the second intercooler 38 enters the evaporator 5, evaporates there, merges with the gas refrigerant flowing from the return pipe 19, and is sucked into the multi-stage compressor 1.

A Mollier diagram of this refrigeration cycle is shown in FIG. The liquid refrigerant extracted in the state of J from the first intercooler 35 is cooled to the stator 3 of the electric motor 2 to be in the state of P through the system shown by the broken line. This refrigerant is separated into gas and liquid by the second intercooler 38, and the separated liquid refrigerant is depressurized by the expansion mechanism 39 in the state of Q, and is then supplied to the evaporator 5 in the state of R by being depressurized.

The separated gas refrigerant is in the state of S in the rotor 4
And cooled to a state T, and throttled by the automatic valve 20 to a state U,
It merges with the gas refrigerant from the evaporator 5 and is sucked into the multi-stage compressor 1 in the state of V, and is compressed by the lower stage impeller 27 to be in the state of B ′. Other configurations and operations are the same as those of the conventional one shown in FIG. 2, and corresponding members are denoted by the same reference numerals and description thereof is omitted.

[0024]

According to the present invention, the total amount of the liquid refrigerant cooled by the first intercooler is supplied to the stator of the electric motor to cool it, and the total amount of the gas refrigerant evaporated by the second intercooler is reduced. Is supplied to the rotor of the motor to cool the rotor, so that the motor can be effectively cooled without deteriorating the efficiency of the refrigerator.

The differential pressure between the suction pressure of the multistage compressor and the intermediate suction pressure is maintained at a certain level or more by an intermediate suction valve interposed in the intermediate suction pipe, and the rotor of the motor is controlled by an automatic valve interposed in the return pipe. If the temperature of the gas refrigerant after cooling is maintained at a certain value or less, it is possible to stably secure a sufficient temperature and amount of the refrigerant for cooling the electric motor.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram of a conventional refrigerator.

FIG. 3 is a Mollier diagram of the present invention and a conventional refrigerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multistage compressor 2 Electric motor 34 Closed casing 42, 43 chambers 3 Stator 4 Rotor 5 Evaporator 6 Condenser 35 First intercooler 36 Throttle mechanism 37 Eliminator 38 Second intermediate cooler 39 Throttle mechanism 40 Eliminator 11 Intermediate suction Pipe 8 Intermediate suction valve 19 Return pipe 20 Automatic valve

Claims (2)

[Claims] 1. A refrigerator comprising a multi-stage compressor driven by a hermetic motor cooled by a refrigerant, a condenser, and an evaporator, wherein the liquid refrigerant condensed by the condenser is subjected to a first intermediate pressure. A first intercooler is provided for cooling by reducing the pressure, and the gas refrigerant evaporated in the first intercooler is returned to an intermediate stage of the multi-stage compressor through an intermediate suction pipe, and the first intermediate cooling is performed. Supplying the liquid refrigerant cooled by the heater to the stator of the hermetic motor to cool it, and reducing the liquid refrigerant after cooling the stator to a second intermediate pressure lower than the first intermediate pressure. Providing a second intercooler for cooling by
The liquid refrigerant cooled by the second intercooler is supplied to the evaporator, and the gas refrigerant evaporated by the second intercooler is supplied to the rotor of the hermetic motor to cool it. Characterized refrigerator. 2. An intermediate suction pipe having an intermediate suction valve for maintaining a differential pressure between the suction pressure of the multi-stage compressor and the intermediate suction pressure at a certain level or more and cooling a rotor of the hermetic motor. 2. The refrigerator according to claim 1, wherein an automatic valve for maintaining the temperature of the gas refrigerant at a certain value or less is interposed in a return pipe for returning the gas refrigerant to a downstream side of the evaporator.