High Efficiency Ejector Cycle

Abstract

A system has a compressor ( 22 ), a heat rejection heat exchanger ( 30 ), first and second ejectors ( 38, 202 ), first and second heat absorption heat exchangers ( 64, 220 ), and first and second separators ( 118, 210 ). The heat rejection heat exchanger is coupled to the compressor to receive refrigerant compressed by the compressor. The first ejector has a primary inlet coupled to the heat rejection exchanger to receive refrigerant, a secondary inlet, and an outlet. The first separator has an inlet coupled to the out let of the first ejector to receive refrigerant from the first ejector. The first separator has a gas outlet coupled to the compressor to return refrigerant to the compressor. The first separator has a liquid outlet coupled to the secondary inlet of the ejector to deliver refrigerant to the first ejector. The first heat absorption heat exchanger is coupled to the liquid outlet of the first separator to receive refrigerant and to the secondary inlet of the first ejector to deliver refrigerant to the first ejector. The second ejector has a primary inlet coupled to the liquid outlet of the first separator to receive refrigerant, a secondary inlet, and an outlet. The second separator has an inlet coupled to an outlet of the second ejector to receive refrigerant from the second ejector, a gas outlet coupled to the compressor to return refrigerant to the compressor, and a liquid outlet. The second heat absorption heat exchanger is coupled to the liquid outlet of the second separator to receive refrigerant and to the secondary inlet of the second ejector to deliver refrigerant to the second ejector.

What is claimed is: 
     
         1 . A system ( 200 ) comprising:
 a compressor ( 22 );   a heat rejection heat exchanger ( 30 ) coupled to the compressor to receive refrigerant compressed by the compressor;   a first ejector ( 38 ) having:
 a primary inlet ( 40 ) coupled to the heat rejection heat exchanger to receive refrigerant; 
 a secondary inlet ( 42 ); and 
 an outlet ( 44 ); 
   a first separator ( 48 ) having:
 an inlet ( 58 ) coupled to the outlet of the first ejector to receive refrigerant from the first ejector; 
 a gas outlet ( 54 ) coupled to the compressor to return refrigerant to the compressor; and 
 a liquid outlet ( 52 ); 
   a first heat absorption heat exchanger ( 64 ) coupled to the liquid outlet of the first separator to receive refrigerant and coupled to the secondary inlet of the first ejector to deliver refrigerant to the first ejector;   a second ejector ( 202 ) having:
 a primary inlet ( 204 ) coupled to the liquid outlet of the first separator to receive refrigerant; 
 a secondary inlet ( 206 ); and 
 an outlet ( 208 ); 
   a second separator ( 210 ) having:
 an inlet ( 212 ) coupled to the outlet of the second ejector to receive refrigerant from the second ejector; 
 a gas outlet ( 216 ) coupled to the compressor to return refrigerant to the compressor; and 
 a liquid outlet ( 214 ); and 
   a second heat absorption heat exchanger ( 220 ) coupled to the liquid outlet of the second separator to receive refrigerant and to the secondary inlet of the second ejector to deliver refrigerant.   
     
     
         2 . The system of  claim 1  further comprising:
 a first expansion device ( 70 ) between the first separator liquid outlet ( 52 ) and the first heat absorption heat exchanger ( 64 ) inlet ( 66 ); and 
 a second expansion device ( 226 ) between the second separator ( 210 ) liquid outlet ( 214 ) and the second evaporator ( 220 ) inlet ( 222 ). 
 
     
     
         3 . The system of  claim 1  wherein:
 the first and second separators are gravity separators. 
 
     
     
         4 . The system of  claim 1  wherein:
 the system has no other separator. 
 
     
     
         5 . The system of  claim 1  wherein:
 the system has no other ejector. 
 
     
     
         6 . The system of  claim 1  wherein:
 the system has no other compressor. 
 
     
     
         7 . The system of  claim 1  wherein:
 the gas outlet ( 54 ) of the first separator feeds an economizer port of the compressor; and 
 the gas outlet ( 216 ) of the second separator feeds a suction port of the compressor. 
 
     
     
         8 . The system of  claim 1  wherein:
 the first heat absorption heat exchanger is in a first refrigerated space; and 
 the second heat absorption heat exchanger is in a second refrigerated space. 
 
     
     
         9 . The system of  claim 1  wherein:
 the refrigerant comprises at least 50% carbon dioxide, by weight. 
 
     
     
         10 . A method for operating the system of  claim 1  comprising running the compressor in a first mode wherein:
 the refrigerant is compressed in the compressor; 
 refrigerant received from the compressor by the heat rejection heat exchanger rejects heat in the heat rejection heat exchanger to produce initially cooled refrigerant; 
 the initially cooled refrigerant passes through the first ejector; and 
 a liquid discharge of the first separator is split into a first portion passing to the first ejector secondary inlet ( 42 ) and a second portion passing to the primary inlet ( 204 ) of the second ejector. 
 
     
     
         11 . The method of  claim 10  wherein:
 the first portion of the liquid discharge of the first separator passes to the first ejector secondary inlet through an expansion device ( 70 ) followed by the first heat absorption heat exchanger ( 64 ); and 
 the second portion of the liquid discharge of the first separator passes to the primary inlet of the second ejector via a second expansion device ( 226 ) followed by the second heat absorption heat exchanger ( 220 ). 
 
     
     
         12 . The method of  claim 10  wherein:
 a gas discharge of the first separator passes to an economizer port of the compressor; and 
 a gas discharge of the second separator passes to a suction port of the compressor. 
 
     
     
         13 . A system ( 200 ) comprising:
 a compressor ( 22 );   a heat rejection heat exchanger ( 30 ) coupled to the compressor to receive refrigerant compressed by the compressor;   a first ejector ( 38 ) having:
 a primary inlet ( 40 ) coupled to the heat rejection heat exchanger to receive refrigerant; 
 a secondary inlet ( 42 ); and 
 an outlet ( 44 ); 
   a first heat absorption heat exchanger ( 64 ) coupled to the outlet of the first ejector to receive refrigerant;   a second ejector ( 202 ) having:
 a primary inlet ( 204 ); 
 a secondary inlet ( 206 ); and 
 an outlet ( 208 ); 
   a second heat absorption heat exchanger ( 220 ) coupled to the outlet of the second ejector to receive refrigerant; and   means for passing refrigerant from the outlet of the first ejector to the primary inlet of the second ejector.   
     
     
         14 . The system of  claim 13  wherein:
 the means is also means for returning refrigerant from the outlet of the first ejector to the secondary inlet of the first ejector. 
 
     
     
         15 . The system of  claim 13  wherein:
 the means comprises a first separator ( 48 ) and conduits branching from a liquid outlet ( 52 ) of the second separator to respectively feed the first ejector secondary inlet via the first heat rejection heat exchanger and directly feed the second ejector primary inlet.