Refrigeration system

Abstract

Disclosed is a CO 2 based refrigeration system including a condenser for transferring heat from a CO 2 refrigerant of the refrigeration system to an air stream. The system further includes a metering device downstream of the condenser and a bypass arrangement. The metering device is configured to create a pressure drop so that part of the refrigerant liquifies, when received in a supercritical state, from the condenser such that a liquid component and a flash gas component are generated. The bypass arrangement includes a valve and a bypass line to allow the refrigerant to bypass the metering device.

What is claimed is: 
     
         1 . A CO 2  based refrigeration system comprising:
 a condenser configured to transfer heat from a CO 2  refrigerant of the refrigeration system to an air stream;   a metering device downstream of the condenser, the metering device configured to create a pressure drop so that part of the refrigerant liquifies, when received in a supercritical state, from the condenser such that a liquid component and a flash gas component are generated; and   a bypass arrangement configured to allow the refrigerant to bypass the metering device, wherein the bypass arrangement comprises a valve and a bypass line.   
     
     
         2 . The refrigeration system according to  claim 1 , wherein the valve is configurable between:
 a first position in which refrigerant bypasses the metering device; and   a second position in which the refrigerant passes through the metering device.   
     
     
         3 . The refrigeration system according to  claim 2 , wherein the valve is disposed on the bypass line. 
     
     
         4 . The refrigeration system according to  claim 1 , further comprising an indirect evaporative cooler arranged to cool an ambient air stream without changing its moisture content, the indirect evaporative cooler being arranged to supply the cooled ambient air to the condenser to facilitate the transfer of heat from the CO 2  refrigerant, wherein the indirect evaporative cooler comprises:
 a first channel for receipt of a first ambient air stream from an air source;   a second channel separate to the first channel, the second channel for receipt of a second air stream and comprising a wetted surface for supplying water to the second air stream by way of evaporation;   a heat exchanger for exchanging heat between the first and second channels; and   a diverter to divert at least a portion of the first ambient air stream into the second channel, whereby the second air stream comprises the diverted portion of the first ambient air stream, said diverter being located at an output end of the first channel such that the portion of the first ambient air stream diverted into the second channel is diverted into the input end of the second channel, the first and second channels being configured such that the first ambient air stream flows through the first channel in a direction opposite to the flow of the second air stream in the second channel;   wherein the second channel is separated from the first channel by a water-impermeable wall configured so that the first ambient air stream received in the first channel is separated from the second air stream in the second channel.   
     
     
         5 . The refrigeration system according to  claim 4 , wherein the first air stream of the indirect evaporative cooler comprises the cooled ambient air supplied to the condenser for condensing of the CO 2  refrigerant. 
     
     
         6 . The refrigeration system according to  claim 4 , comprising a controller arranged to control the supply of cooled ambient air to the condenser. 
     
     
         7 . The refrigeration system according to  claim 6 , comprising a fan to move the ambient air through the indirect evaporative cooler. 
     
     
         8 . The refrigeration system according to  claim 7 , wherein the controller is configured to control the fan to control movement of the ambient air through the indirect evaporative cooler. 
     
     
         9 . The refrigeration system according to  claim 6 , wherein the controller is configured to control a condenser fan for moving cooled ambient air across coils of the condenser. 
     
     
         10 . The refrigeration system according to  claim 6  wherein the controller is configured to control the supply of cooler ambient air to the condenser based on the relative humidity and temperature of the air source. 
     
     
         11 . The refrigeration system according to  claim 6  wherein the controller is configured to maintain the temperature of the refrigerant in the condenser below a predetermined threshold temperature. 
     
     
         12 . The refrigeration system according to  claim 4  comprising one or more sensors for measuring the temperature and relative humidity of the air source. 
     
     
         13 . A method of operating a CO 2  based refrigeration system, the method comprising:
 determining whether CO 2  refrigerant being discharged from the condenser of the refrigeration system is in a supercritical state; and   controlling the system so as to:
 create a pressure drop so that part of the refrigerant liquifies by way of a throttling process when the CO 2  refrigerant is determined to be in the supercritical state, and 
 bypass the throttling process when the CO 2  is determined to not be in the supercritical state. 
   
     
     
         14 . The method of  claim 13 , further comprising:
 supplying a first ambient air stream from an air source;   diverting at least a portion of the first ambient air stream so that a second air stream comprises the diverted portion of the first ambient air stream;   cooling the second air stream by moving the second air stream across a wetted surface in a direction opposite to a flow of the first ambient air stream;   transferring heat between the first ambient air stream and the second air stream to cool the first ambient air stream without changing its moisture content; and   transferring heat between at least a portion of the first ambient air stream and CO 2  refrigerant in a condenser of the refrigeration system.