Refrigerator and operation method during precooling of refrigerator

Abstract

A refrigerator 1 of the present disclosure includes: at least two compressors, namely, a low-stage compressor C 1 and a high-stage compressor C 3 ; an expander T; a cooling part 2 for cooling a cooling object R 2 with a refrigerant R 1 expanded by the expander T; a refrigerant circulation line 8 for circulating the refrigerant; a bypass line 31 connected to a high-pressure line and a low-pressure line of the refrigerant circulation line 8 ; a bypass valve 32 ; a first temperature sensor 33 for detecting a temperature of the refrigerant R 1 on an inlet side of the expander T or a second temperature sensor 34 for detecting the temperature of the refrigerant R 1 on an outlet side of the expander T; and a controller 40 for controlling an opening degree of the bypass valve 32 and a rotation speed of the refrigerator 1 based on a detection result of the first temperature sensor 33 or the second temperature sensor 34.

1 - 12 . (canceled) 
     
     
         13 . A refrigerator, comprising:
 a low-stage compressor for compressing a refrigerant;   an expander-integrated compressor which includes a high-stage compressor for further compressing the refrigerant, and an expander for expanding the refrigerant compressed by the high-stage compressor, the expander being coupled to the high-stage compressor via a rotational shaft drivable by a motor;   a cooling part for cooling a cooling object with the refrigerant expanded by the expander;   a refrigerant circulation line for circulating the refrigerant, the refrigerant circulation line including a low-pressure line ranging from the expander to the low-stage compressor via the cooling part, an intermediate-pressure line ranging from the low-stage compressor to the high-stage compressor, and a high-pressure line ranging from the high-stage compressor to the expander;   a bypass line which is connected at one end to a first connection portion disposed on the high-pressure line and is connected at another end to a second connection portion disposed on the low-pressure line; and   a bypass valve disposed on the bypass line and capable of adjusting a flow rate of the refrigerant flowing through the bypass line by adjusting an opening degree.   
     
     
         14 . The refrigerator according to  claim 13 , comprising:
 a cold recovery heat exchanger for cooling the refrigerant flowing through the high-pressure line with the refrigerant in the low-pressure line having passed through the cooling part, the cold recovery heat exchanger being disposed on the high-pressure line;   a temperature sensor for detecting a temperature of the refrigerant flowing between the cold recovery heat exchanger and the expander of the high-pressure line; and   a controller for controlling the opening degree of the bypass valve and a rotation speed of the rotational shaft based on a detection result of the temperature sensor.   
     
     
         15 . The refrigerator according to  claim 13 , comprising:
 a temperature sensor for detecting a temperature of the refrigerant between the cooling part and the expander of the low-pressure line; and   a controller for controlling the opening degree of the bypass valve and a rotation speed of the rotational shaft based on a detection result of the temperature sensor.   
     
     
         16 . The refrigerator according to  claim 14 ,
 wherein the controller is configured to:   control the bypass valve such that the opening degree is decreased stepwise until the temperature of the refrigerant detected by the temperature sensor reaches a preset first target temperature; and control the rotation speed such that a rate of decrease in the temperature of the refrigerant detected by the temperature sensor is maintained constant, in an initial operation period from a start of startup to a completion of a precooling operation of the refrigerator.   
     
     
         17 . The refrigerator according to  claim 14 ,
 wherein the controller is configured to:   control the bypass valve such that the opening degree is decreased continuously until the temperature of the refrigerant detected by the temperature sensor reaches a preset first target temperature; and control the rotation speed such that a rate of decrease in the temperature of the refrigerant detected by the temperature sensor is maintained constant, in an initial operation period from a start of startup to a completion of a precooling operation of the refrigerator.   
     
     
         18 . The refrigerator according to  claim 16 ,
 wherein the controller is configured to:   control the bypass valve such that the opening degree becomes 0% at a stage when the temperature of the refrigerant detected by the temperature sensor reaches the first target temperature; and control the rotation speed such that the rate of decrease in the temperature of the refrigerant detected by the temperature sensor is maintained constant while maintaining the opening degree at 0% until the temperature of the refrigerant, which is detected by the temperature sensor and is lower than the first target temperature, reaches a second target temperature set lower than the first target temperature.   
     
     
         19 . The refrigerator according to  claim 18 , comprising:
 a heat exchanger for exchanging heat between the refrigerant and a secondary refrigerant for cooling the cooling object; and   a secondary refrigerant temperature sensor for detecting a temperature of the secondary refrigerant,   wherein the controller is configured to:   control the rotation speed based on a detection result of the secondary refrigerant temperature sensor, if the temperature of the refrigerant detected by the temperature sensor is lower than the second target temperature.   
     
     
         20 . The refrigerator according to  claim 13 , comprising:
 a cold recovery heat exchanger for cooling a refrigerant in the high-pressure line with a refrigerant having been used to cool the cooling object in the cooling part;   a buffer line which is connected at one end to a third connection portion disposed between the cold recovery heat exchanger and the high-stage compressor of the high-pressure line, and is connected at another end to a fourth connection portion disposed between the low-stage compressor and the cold recovery heat exchanger of the low-pressure line;   a buffer tank disposed on the buffer line and capable of storing the refrigerant sent from the high-pressure line;   a high-pressure side buffer valve disposed between the buffer tank and the third connection portion of the buffer line;   a low-pressure side buffer valve disposed between the buffer tank and the fourth connection portion of the buffer line;   a first pressure sensor for detecting a pressure of the refrigerant between the first connection portion and the third connection portion of the high-pressure line;   a second pressure sensor for detecting an internal pressure of the buffer tank; and   a controller for controlling opening degrees of the high-pressure side buffer valve and the low-pressure side buffer valve according to detection results of the first pressure sensor and the second pressure sensor.   
     
     
         21 . The refrigerator according to  claim 13 , comprising:
 a cold recovery heat exchanger for cooling the refrigerant flowing through the high-pressure line with the refrigerant having passed through the cooling part, the cold recovery heat exchanger being disposed on the high-pressure line;   a temperature sensor for detecting a temperature of the refrigerant flowing between the cold recovery heat exchanger and the expander of the high-pressure line; and   a controller for controlling the opening degree of the bypass valve and a rotation speed of the rotational shaft based on a detection result of the temperature sensor,   wherein the controller is configured to control the bypass valve such that the opening degree is decreased stepwise or continuously until the temperature of the refrigerant detected by the temperature sensor reaches a preset first target temperature, in an initial operation period from a start of startup to a completion of a precooling operation of the refrigerator.   
     
     
         22 . An operation method in an initial operation period from startup to a completion of precooling of a refrigerator that includes:
 a low-stage compressor for compressing a refrigerant;   an expander-integrated compressor which includes a high-stage compressor for further compressing the refrigerant, and an expander for expanding the refrigerant compressed by the high-stage compressor, the expander being coupled to the high-stage compressor via a rotational shaft drivable by a motor;   a cooling part for cooling a cooling object with the refrigerant expanded by the expander;   a refrigerant circulation line for circulating the refrigerant, the refrigerant circulation line including a low-pressure line ranging from the expander to the low-stage compressor via the cooling part, an intermediate-pressure line ranging from the low-stage compressor to the high-stage compressor, and a high-pressure line ranging from the high-stage compressor to the expander;   a bypass line which is connected at one end to a first connection portion disposed on the high-pressure line and is connected at another end to a second connection portion disposed on the low-pressure line;   a bypass valve disposed on the bypass line and capable of adjusting a flow rate of the refrigerant flowing through the bypass line by adjusting an opening degree;   a temperature sensor for detecting a temperature of the refrigerant flowing between the cold recovery heat exchanger and the expander of the high-pressure line or a temperature of the refrigerant between the cooling part and the expander of the low-pressure line; and   a controller for controlling the opening degree of the bypass valve and a rotation speed of the rotational shaft based on a detection result of the temperature sensor, the operation method during precooling of the refrigerator, comprising:   a startup operation step of starting an operation by setting the rotation speed of the rotational shaft at a preset rotation speed lower than a rotation speed during a steady operation after the initial operation period and setting the opening degree of the bypass valve at a preset opening degree;   a bypass control operation step of controlling, with the controller, such that the opening degree of the bypass valve is decreased until the temperature of the refrigerant detected by the temperature sensor reaches a preset first target temperature;   a non-bypass control operation step of cooling, at a stage when the temperature of the refrigerant reaches the first target temperature, the refrigerant until the temperature of the refrigerant reaches a preset second target temperature from the first target temperature, at a 0-percent opening degree of the bypass valve; and   a cooling velocity control step of controlling, with the controller, the rotation speed such that a rate of decrease in the temperature of the refrigerant is maintained constant at least in the bypass control operation step among the bypass control operation step and the non-bypass control operation step.   
     
     
         23 . The operation method during precooling of the refrigerator according to  claim 22 ,
 wherein the bypass control operation step includes controlling, with the controller, such that the opening degree of the bypass valve is decreased stepwise until the temperature of the refrigerant detected by the temperature sensor reaches the preset first target temperature.   
     
     
         24 . The operation method during precooling of the refrigerator according to  claim 22 ,
 wherein the bypass control operation step includes controlling, with the controller, such that the opening degree of the bypass valve is decreased continuously until the temperature of the refrigerant detected by the temperature sensor reaches the preset first target temperature.   
     
     
         25 . The operation method during precooling of the refrigerator according to  claim 22 ,
 wherein the refrigerator includes:   a heat exchanger for exchanging heat between the refrigerant and a secondary refrigerant for cooling the cooling object; and   a secondary refrigerant temperature sensor for detecting a temperature of the secondary refrigerant, and   wherein the controller includes:   a main cooling operation switching step of controlling the rotation speed based on a detection result of the secondary refrigerant temperature sensor, if the temperature of the refrigerant detected by the temperature sensor is lower than the second target temperature.