Refrigeration apparatus

Abstract

There is disclosed a refrigeration apparatus comprising a refrigerant circuit, the refrigerant circuit comprising a compressor comprising a compressor fan and a motor to drive the compressor fan; a condensing device disposed downstream of the compressor, the condensing device comprising a condenser and a sub-cooler; an expansion valve disposed downstream of the condensing device; an evaporator disposed between the expansion valve and the compressor; and a main refrigerant line fluidically connecting, in a loop in series: the compressor, condensing device, expansion valve and evaporator. A motor cooling line comprising a motor cooling valve fluidically connects the sub-cooler to the motor to tap refrigerant from the main refrigerant line to cool the motor and is further connected to the main refrigerant line at a return point which is upstream of the compressor fan to return refrigerant to the main refrigerant line at the compressor fan. A bypass line fluidically connects an outlet of the condenser to the expansion valve to bypass the sub-cooler, wherein the bypass line comprises a bypass valve to selectively permit refrigerant in the main refrigerant line to bypass the sub-cooler.

1 . A refrigeration apparatus comprising a refrigerant circuit, the refrigerant circuit comprising:
 a compressor comprising a compressor fan and a motor to drive the compressor fan;   a condensing device disposed downstream of the compressor, the condensing device comprising a condenser and a sub-cooler;   an expansion valve disposed downstream of the condensing device;   an evaporator disposed between the expansion valve and the compressor;   a main refrigerant line fluidically connecting, in a loop in series: the compressor, condensing device, expansion valve and evaporator; and   a motor cooling line comprising a motor cooling valve, the motor cooling line fluidically connecting the sub-cooler to the motor to tap refrigerant from the main refrigerant line to cool the motor, wherein the motor cooling line is further connected to the main refrigerant line at a return point which is upstream of the compressor fan to return refrigerant to the main refrigerant line at the compressor fan;   wherein the refrigerant circuit further comprises a bypass line fluidically connecting an outlet of the condenser to the expansion valve to bypass the sub-cooler, wherein the bypass line comprises a bypass valve to selectively permit refrigerant in the main refrigerant line to bypass the sub-cooler.   
     
     
         2 . A refrigeration apparatus according to  claim 1 , wherein the compressor comprises an inverter, and wherein the sub-cooler is connected to the inverter by an inverter cooling line comprising an inverter cooling valve, and wherein the inverter cooling line is further connected to the main refrigerant line at the return point to direct refrigerant from the inverter to the main refrigerant line at the compressor fan. 
     
     
         3 . A refrigeration apparatus according to  claim 1 , comprising a controller configured to control opening and closing of the bypass valve. 
     
     
         4 . A refrigeration apparatus according to  claims 2  wherein the controller is configured to control opening and closing of the inverter cooling valve. 
     
     
         5 . A refrigeration apparatus according to  claim 3 , wherein the bypass valve is a modulating valve, and wherein the controller is configured to control the bypass valve to control the flow rate of refrigerant through the bypass valve. 
     
     
         6 . A refrigeration apparatus according to  claim 3 , comprising a first pressure sensor arranged to monitor the pressure of refrigerant exiting the sub-cooler, and a second pressure sensor arranged to monitor the pressure in the main refrigerant line at the return point;
 wherein the controller is arranged to receive a first pressure parameter from the first pressure sensor, and a second pressure parameter from the second pressure sensor, and to control the bypass valve based on the first pressure parameter and the second pressure parameter.   
     
     
         7 . A refrigeration apparatus according to  claim 3 , comprising a first pressure sensor arranged to monitor the pressure of refrigerant exiting the sub-cooler, a second pressure sensor arranged to monitor the pressure in the main refrigerant line at an inlet of the compressor, and a third pressure sensor arranged to monitor the pressure in the main refrigerant line at an outlet of the compressor;
 wherein the controller is arranged to receive a first pressure parameter from the first pressure sensor, a second pressure parameter from the second pressure sensor, and a third pressure parameter from the third pressure sensor, and wherein the controller is arranged to control the bypass valve based on the first pressure parameter, the second pressure parameter, and the third pressure parameter.   
     
     
         8 . A refrigeration apparatus according to  claim 1 , wherein the compressor is a two-stage compressor comprising a first stage compressor fan and a second stage compressor fan, and wherein the return point is between a first stage compressor fan and the second stage compressor fan. 
     
     
         9 . A refrigeration apparatus according to  claim 3 , wherein the controller is configured to control opening and closing of the motor cooling valve. 
     
     
         10 . A method of operating a refrigeration apparatus according to  claim 1 , the method comprising:
 determining whether insufficient refrigerant is being delivered from the sub-cooler to the compressor; and   in response to determining that insufficient refrigerant is being delivered from the sub-cooler to the compressor, controlling the bypass valve to increase the flow rate of refrigerant through the bypass valve.   
     
     
         11 . A method according to  claim 10 , wherein determining whether insufficient refrigerant is being delivered to the compressor includes:
 monitoring a first pressure parameter relating to the pressure of refrigerant in the main refrigerant line at an outlet of the sub-cooler;   monitoring a second pressure parameter relating to the pressure in the main refrigerant line at a return point upstream of a compressor fan; and   determining whether there is insufficient refrigerant being delivered to the compressor based on the first pressure parameter and the second pressure parameter.   
     
     
         12 . A method according to  claim 11 , wherein the second pressure parameter relates to the pressure in the main refrigerant line at a return point between a first stage compressor fan and a second stage compressor fan of a two-stage compressor. 
     
     
         13 . A method according to  claim 11 , wherein determining whether there is insufficient refrigerant being delivered to the compressor includes:
 calculating a difference parameter relating to a difference between the first pressure parameter and the second pressure parameter;   comparing the difference parameter to a first threshold; and   if the difference parameter is below the first threshold, determining that there is insufficient refrigerant being delivered to the compressor.   
     
     
         14 . A method according to  claim 10 , wherein the method further comprises determining whether there is too much refrigerant being delivered to the compressor, and in response to determining that there is too much refrigerant being delivered to the compressor, reducing the flow of refrigerant through the bypass valve. 
     
     
         15 . A method according to  claim 14 , wherein determining whether there is too much refrigerant being delivered to the compressor comprises:
 comparing the difference parameter to a second threshold; and   if the difference parameter is above the second threshold, determining that there is too much refrigerant being delivered to the compressor.