Refrigeration circuit

Abstract

A refrigeration circuit has a mono- or multi-component refrigerant, especially CO 2 , circulating therein, said refrigeration circuit enabling an transcritical operation, said refrigeration circuit comprising, in the direction of refrigerant flow, a compressor unit, a condenser/gascooler, a high pressure control valve, a collecting container, and at least one evaporator having an expansion device connected upstream thereof, wherein a flashgas line having a medium pressure control valve arranged therein is provided between an upper portion of the collecting container and the suction line leading to the compressor unit, wherein a temperature, pressure or liquid level sensor is provided in or at the collecting container, wherein a bypass line having a medium pressure holding valve arranged therein is provided connecting the line between the condenser/gascooler and the high pressure control valve to the line between the collecting container and the expansion device(s), and wherein a control unit is provided said control unit being configured to open the medium pressure holding valve when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.

1 . A refrigeration circuit having a mono- or multi-component refrigerant, especially CO 2 , circulating therein, said refrigeration circuit enabling an transcritical operation, said refrigeration circuit comprising, in the direction of refrigerant flow:
 a compressor unit;   a condenser/gascooler;   a high pressure control valve;   a collecting container; and   at least one evaporator having an expansion device connected upstream thereof;   wherein a flashgas line having a medium pressure control valve arranged therein is provided between an upper portion of the collecting container and a suction line leading to the compressor unit, characterized in that:   a temperature, pressure or liquid level sensor is provided in or at the collecting container;   a medium pressure holding valve is provided; and   a control unit is provided, said control unit being configured to open the medium pressure holding valve when the temperature or pressure in the collecting, container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.   
     
     
         2 . The refrigeration circuit of  claim 1 , wherein the medium pressure holding valve is disposed in a bypass line connecting a line between the condenser/gascooler and the high pressure control valve to a line between the collecting container and the expansion device(s). 
     
     
         3 . The refrigerant circuit of  claim 1  further comprising a bypass line is provided connecting a line after the high pressure control valve to a line between the collecting container and the expansion device(s). 
     
     
         4 . The refrigerant circuit of  claim 3  wherein the medium pressure holding valve is arranged in the line after a branch-off point of the bypass line and before the collecting container. 
     
     
         5 . The refrigeration circuit of  claim 3  wherein the medium pressure holding valve is disposed in the bypass line. 
     
     
         6 . The refrigeration circuit of  claim 3  wherein the medium pressure holding valve is arranged in a line after the collecting container and before a refeed point of the bypass line. 
     
     
         7 . The refrigeration circuit of  claim 6 , wherein a phase-change separator is placed at the branch-off point of the bypass line. 
     
     
         8 . The refrigeration circuit of  claim 1 , further comprising:
 a bypass line connecting the pressure line after the compressor unit to the line between the condenser/gascooler and the high pressure control valve;   wherein the medium pressure holding valve is arranged in the bypass line.   
     
     
         9 . The refrigeration circuit of  claim 1 , further comprising:
 a bypass line having connecting a pressure line to the collecting container or to a flashgas line before the medium pressure control valve;   wherein the medium pressure holding valve is arranged in the bypass line.   
     
     
         10 . The refrigeration circuit of  claim 1 , wherein the compressor unit comprises a set of compressors. 
     
     
         11 . The refrigeration circuit of  claim 1 , wherein at least two evaporators having a respective expansion device connected upstream thereof are connected in parallel. 
     
     
         12 . A refrigeration circuit having a mono- or multi-component refrigerant, especially CO 2 , circulating therein, said refrigeration circuit enabling an transcritical operation, said refrigeration circuit comprising, in the direction of refrigerant flow:
 a compressor unit;   a condenser/gas cooler;   a high pressure control valve;   a collecting container; and   at least one evaporator having an expansion device connected upstream thereof;   wherein a flashgas line having a medium pressure control valve arranged therein is provided between an upper portion of the collecting container and a suction line leading to the compressor unit, characterized in that:   a temperature, pressure or liquid level sensor is provided in or at the collecting container;   a collecting container heating unit arranged in the collecting container;   and a control unit is provided said control unit being configured to effect heating operation of the collecting container heating unit when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.   
     
     
         13 . The refrigeration circuit of  claim 12 , wherein the compressor unit comprises a set of compressors. 
     
     
         14 . The refrigeration circuit of  claim 12 , wherein at least two evaporators having a respective expansion device connected upstream thereof are connected in parallel. 
     
     
         15 . A refrigeration circuit having a mono- or multi-component refrigerant, especially CO 2 , circulating therein, said refrigeration circuit enabling an transcritical operation, said refrigeration circuit comprising, in the direction of refrigerant flow:
 a compressor unit;   a condenser/gascooler with at least one fan leading air over its surface;   a high pressure control valve;   a collecting container; and   at least one evaporator having an expansion device connected upstream thereof;   wherein a flashgas line having a medium pressure control valve arranged therein is provided between an upper portion of the collecting container and the suction line leading to the compressor unit, characterized in that:   a temperature, pressure or liquid level sensor is provided in or at the collecting container;   and a control unit is provided said control unit being configured to lower the performance of the fan(s) when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.   
     
     
         16 . The refrigeration circuit of  claim 15 , wherein the control unit comprises a variable speed drive for the fan(s). 
     
     
         17 . The refrigeration circuit of  claim 15 , wherein the compressor unit comprises a set of compressors. 
     
     
         18 . The refrigeration circuit of  claim 15 , wherein at least two evaporators having a respective expansion device connected upstream thereof are connected in parallel.