Refrigeration System And Method For Operating A Refrigeration System

Abstract

A refrigeration system ( 2 ) comprises a condenser/gas cooler ( 4 ), an intermediate expansion device ( 6 ) and a refrigerant collecting container ( 8 ); a normal refrigeration branch ( 10 ) connecting the refrigerant collecting container ( 8 ) to the condenser/gas cooler ( 4 ) said normal refrigeration branch ( 12 ) comprising a first expansion device ( 12 ), a first evaporator ( 14 ) and a compressor unit ( 16 ) of the normal refrigeration branch ( 10 ); a freezing branch ( 18 ) connecting the refrigerant collecting container ( 8 ) to the condenser/gas cooler ( 4 ), said freezing branch ( 18 ) comprising a second expansion device ( 20 ), a second evaporator ( 22 ), and a first compressor unit ( 24 ) and a second compressor unit ( 26 ) of said freezing branch ( 18 ), the first and second compressor units ( 24, 26 ) of the freezing branch ( 18 ) being connected in series. A flash gas line ( 28 ) is provided connecting the gas space of the refrigerant collecting container ( 8 ) to the line connecting the first compressor unit ( 24 ) to the second compressor unit ( 26 ) of said freezing branch ( 18 ). Refrigerant conduits for connecting said elements and for circulating a refrigerant therethrough are also provided.

1 . Refrigeration system, comprising:
 a condenser/gas cooler, an intermediate expansion device and a refrigerant collecting container;   a normal refrigeration branch connecting the refrigerant collecting container to the condenser/gas cooler, said normal refrigeration branch comprising a first expansion device, a first evaporator and a compressor unit of the normal refrigeration branch;   a freezing branch connecting the refrigerant collecting container to condenser/gas cooler, said freezing branch comprising a second expansion device, a second evaporator, and a first compressor unit and a second compressor unit of said freezing branch, the first and second compressor units of the freezing branch being connected in series,   wherein a flash gas line is provided connecting the gas space of the refrigerant collecting container to the line connecting the first compressor unit to the second compressor unit of said freezing branch;   further comprising refrigerant conduits for connecting said elements and for circulating a refrigerant therethrough.   
     
     
         2 . Refrigeration system according to  claim 1 , further comprising an oil balance line connecting at least one oil sump of the compressor unit of the normal refrigeration branch to at least one of the compressors of the first and second compressor units of the freezing branch. 
     
     
         3 . Refrigeration system according to  claim 2 , wherein the oil balance line connects at least one oil sump of the compressor unit of the normal refrigeration branch to at least one oil sump of the first compressor unit of the freezing branch. 
     
     
         4 . Refrigeration system according to  claim 2 , wherein the oil balance line connects at least one oil sump of the compressor unit of the normal refrigeration branch to the suction side of the first compressor unit of the freezing branch. 
     
     
         5 . Refrigeration system according to  claim 2 , wherein said oil balance line can be switched open or closed by means of at least one valve arranged therein. 
     
     
         6 . Refrigeration system according to  claim 2 , comprising a control unit configured to switch the valve in the oil balance line open if the oil level in the second compressor unit of the freezing branch falls below a predetermined threshold value. 
     
     
         7 . Refrigeration system according to  claim 2 , comprising a control unit configured to switch the valve in the oil balance line open if the oil level in the first compressor unit of the freezing branch falls below a pre-determined threshold value. 
     
     
         8 . Refrigeration system according to  claim 2 , comprising a control unit configured to switch the valve in the oil balance line open if the oil level in the compressor unit of the normal refrigeration branch exceeds a predetermined threshold value. 
     
     
         9 . Refrigeration system according to  claim 2 , comprising a control unit configured to switch the valve in the oil balance line open if the oil level in the compressor unit of the normal refrigeration branch exceeds a predetermined threshold value. 
     
     
         10 . Refrigeration system according to  claim 2 , comprising a control unit configured to switch the valve in the oil balance line open if the oil level in the first compressor unit of the freezing branch falls below a predetermined threshold value. 
     
     
         11 . Refrigeration system according to  claim 2 , wherein the valve is configured to be opened after a predetermined time interval. 
     
     
         12 . Refrigeration system according to  claim 2 , wherein the oil balance line connects at least one oil sump of the compressor unit of the normal refrigeration branch to an outlet of the first compressor unit of the freezing branch. 
     
     
         13 . Refrigeration system according to  claim 2 , wherein the oil balance line connects at least one oil sump of the compressor unit of the normal refrigeration branch to at least one oil sump of the second compressor unit of the freezing branch and to at least one of the compressors of the first compressor unit of the freezing branch. 
     
     
         14 . Refrigeration system according to  claim 2 , wherein the oil balance line connects to at least one oil sump of the first compressor unit of the freezing branch. 
     
     
         15 . Refrigeration system according to  claim 2 , wherein the oil balance line connects to an outlet of the first compressor unit of the freezing branch. 
     
     
         16 . Refrigeration system according to  claim 1 , wherein the second compressor unit of the freezing branch is frequency controlled to match the mass flow from the first compressor unit of the freezing branch and from the flash gas line. 
     
     
         17 . Refrigeration system according to  claim 1 , wherein the refrigerant is C02. 
     
     
         18 . Refrigeration system according to  claim 1 , wherein said first evaporator and said second evaporator are located in refrigerating sales furnitures or cooling/freezing rooms of a supermarket. 
     
     
         19 . Refrigeration system according to  claim 1 , wherein the normal refrigeration branch is parallel to the freezing branch. 
     
     
         20 . Refrigeration system according to  claim 1 , wherein the compressor unit of the normal refrigeration branch is parallel to the first and second compressor units of the freezing branch. 
     
     
         21 . Method for operating a refrigeration system, comprising:
 a condenser/gas cooler, an intermediate expansion device and a refrigerant collecting container, the method comprising:   operating a normal refrigeration branch between the refrigerant collecting container to the condenser/gas cooler, said normal refrigeration branch comprising a first expansion device, a first evaporator and a coin pressor compressor unit of the normal refrigeration branch;   operating a freezing branch between the refrigerant collecting container to the condenser/gas cooler, said freezing branch comprising a second expansion device, a second evaporator, and a first compressor unit and a second compressor unit of said freezing branch, the first and second compressor units of the freezing branch being connected in series, and   feeding flash gas from the gas space of the refrigerant collecting container to the line connecting the first compressor unit to the second compressor unit of said freezing branch by means of a flash gas line.