Dual Temperature Refrigeration Circuit

Abstract

Combined medium and low temperature refrigeration circuit for circulating a refrigerant in a predetermined flow direction includes, in flow direction, a heat-rejecting heat exchanger, a medium temperature refrigeration consumer, a medium pressure vapor separator having a vapor portion and a liquid portion connected to the medium temperature refrigeration consumer unit, a low temperature refrigeration consumer connected to the liquid portion of the medium pressure vapor separator, and a compressor unit having an inlet connected to the vapor portion of the medium pressure vapor separators and the low temperature refrigeration consumer.

1 - 20 . (canceled) 
   
   
       21 . A combined medium and low temperature refrigeration circuit for circulating a refrigerant in a predetermined flow direction comprising, in flow direction:
 a heat rejecting heat exchanger;   a medium temperature refrigeration consumer;   a medium pressure vapor separator having a vapor portion and a liquid portion, the medium pressure vapor separator being connected to the medium temperature refrigeration consumer;   a low temperature refrigeration consumer;   a compressor unit having an inlet connected to the vapor portion of the medium pressure vapor separator and to the low temperature refrigeration consumer,   a medium pressure expansion device; and   an intermediate pressure vapor separator, with the medium pressure expansion device connected to the liquid portion of the medium pressure vapor separator, the liquid portion of the intermediate pressure vapor separator connected to the low temperature refrigeration consumer, and the vapor portion of the intermediate pressure vapor separator connected to the compressor unit.   
   
   
       22 . The refrigeration circuit according to  claim 21 , further comprising a high pressure vapor separator having a vapor portion and a liquid portion between the heat rejecting heat exchanger and the medium temperature refrigeration consumer, wherein the vapor portion is connected to the inlet of the compressor unit and the liquid portion is connected to the medium temperature refrigeration consumer. 
   
   
       23 . The refrigeration circuit according to  claim 22 , further comprising an expansion device between the heat rejecting heat exchanger and a high temperature vapor separator. 
   
   
       24 . The refrigeration circuit according to  claim 22 , further comprising a pressure regulated valve in a line between the vapor portion of the high pressure vapor separator and the compressor unit. 
   
   
       25 . The refrigeration circuit according to  claim 22 , further comprising a refrigeration consumer comprising at least one expansion device and at least one evaporator. 
   
   
       26 . The refrigeration circuit according to  claim 21 , wherein the compressor unit comprises a low pressure compressor set, a medium pressure compressor set, and a high pressure vapor compressor, with the low pressure compressor set being connected to the low temperature refrigeration consumer, the medium pressure compressor set being connected to the vapor portion of the medium pressure vapor separator, and the high pressure vapor compressor being connected to a vapor portion of a high pressure vapor separator. 
   
   
       27 . The refrigeration circuit according to  claim 21 , wherein the compressor unit further comprises an intermediate compressor between the vapor portion of the intermediate pressure vapor separator and the medium pressure compressor set. 
   
   
       28 . The refrigeration circuit according to  claim 21 , further comprising a pressure regulating valve between the vapor portion of the intermediate pressure vapor separator and the compressor unit. 
   
   
       29 . The refrigeration circuit according to  claim 21 , further comprising a superheat sensor associated to an exit of the low temperature refrigeration consumer and connected to a control for securing superheat of the refrigerant. 
   
   
       30 . The refrigeration circuit according to  claim 21 , wherein the refrigerant is carbon dioxide. 
   
   
       31 . A refrigeration apparatus comprising:
 a refrigeration circuit including:   a heat rejecting heat exchanger;   a medium temperature refrigeration consumer;   a medium pressure vapor separator having a vapor portion and a liquid portion, the medium pressure vapor separator being connected to the medium temperature refrigeration consumer;   a low temperature refrigeration consumer;   a compressor unit having an inlet connected to the vapor portion of the medium pressure vapor separator and to the low temperature refrigeration consumer,   a medium pressure expansion device; and   an intermediate pressure vapor separator, with the medium pressure expansion device connected to the liquid portion of the medium pressure vapor separator, the liquid portion of the intermediate pressure vapor separator connected to the low temperature refrigeration consumer, and the vapor portion of the intermediate pressure vapor separator connected to the compressor unit.   
   
   
       32 . A method for operating a combined medium and low temperature refrigeration circuit for circulating a refrigerant in a predetermined flow direction, the refrigeration circuit comprising, in flow direction, a heat rejecting heat exchanger, a medium temperature refrigeration consumer, a low temperature refrigeration consumer, and a compressor unit, each thereof having an inlet and an outlet, respectively, wherein the method comprises the steps of:
 a) separating liquid medium pressure refrigerant leaving the outlet of the medium temperature refrigeration consumer from gaseous medium pressure refrigerant leaving the outlet of the medium temperature refrigeration consumer;   b) directing the gaseous medium pressure refrigerant towards the inlet of the compressor unit;   c) expanding the liquid medium pressure refrigerant to an intermediate pressure;   d) separating liquid intermediate pressure refrigerant from gaseous intermediate pressure refrigerant;   e) directing the gaseous intermediate pressure refrigerant towards the inlet of the compressor unit; and   f) directing the liquid intermediate pressure refrigerant towards the low temperature refrigeration consumer.   
   
   
       33 . The method according to  claim 32 , further comprising the steps of:
 g) separating liquid high pressure refrigerant leaving the outlet of the heat rejecting heat exchanger from gaseous high pressure refrigerant leaving the same outlet;   h) directing the gaseous high pressure refrigerant towards the inlet of the compressor unit; and   i) directing the liquid high pressure refrigerant towards the inlet of the medium temperature refrigeration consumer.   
   
   
       34 . The method according to  claim 33 , further comprising the steps of expanding the high pressure refrigerant leaving the heat rejecting heat exchanger before step g). 
   
   
       35 . The method according to  claim 33 , further comprising the step of regulating the pressure of the gaseous high pressure refrigerant. 
   
   
       36 . The method according to  claim 32 , further comprising the step of regulating the pressure of the gaseous intermediate pressure refrigerant. 
   
   
       37 . The method according to  claim 32 , further comprising the step controlling the superheat of gaseous low pressure refrigerant entering the inlet of the compressor unit. 
   
   
       38 . The method according to  claim 32 , wherein the compressor unit comprises a low pressure compressor set, a medium pressure compressor set, a high pressure vapor compressor, and an intermediate compressor, and wherein gaseous refrigerant leaving the low temperature refrigeration consumer is directed to the low pressure compressor set, the gaseous medium pressure refrigerant is directed to the medium pressure compressor set, gaseous high pressure refrigerant is directed to the high pressure vapor compressor, and the gaseous intermediate pressure refrigerant is directed to the intermediate compressor.