US2013145781A1PendingUtilityA1

Multi-Compressor Refrigeration System and Method for Operating It

46
Individually held — no corporate assignee on recordPriority: May 16, 2011Filed: Apr 27, 2012Published: Jun 13, 2013
Est. expiryMay 16, 2031(~4.8 yrs left)· nominal 20-yr term from priority
Inventors:Lucy Yi Liu
F25B 1/02F25B 2600/021F25B 2400/0751F25B 2400/075F25B 49/022Y02B30/70F25B 9/008F25B 2600/024F25B 1/00
46
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Claims

Abstract

A refrigeration system ( 20 ) has a first compressor ( 24 ) and a second compressor ( 26 ). The second compressor has at least a first condition t least partially in parallel with the first compressor along a refrigerant flowpath. A heat rejection heat exchanger ( 50 ) is downstream of the first and second compressors along the refrigerant flowpath. An expansion device ( 54 ) is downstream of the heat rejection heat exchanger along the refrigerant flowpath. A heat absorption heat exchanger ( 56 ) is downstream of the expansion device along the refrigerant flowpath. The first compressor is a variable speed compressor coupled to a variable speed drive ( 32 ). The second compressor is a fixed speed compressor.

Claims

exact text as granted — not AI-modified
1 . A refrigeration system ( 20 ) comprising:
 a first compressor ( 24 );   a second compressor ( 26 ) having at least a first condition at least partially in parallel with the first compressor along a refrigerant flowpath;   a heat rejection heat exchanger ( 50 ) downstream of the first compressor and second compressor along the refrigerant flowpath;   an expansion device ( 54 ) downstream of the heat rejection heat exchanger along the refrigerant flowpath; and   a heat absorption heat exchanger ( 56 ) downstream of the expansion device along the refrigerant flowpath,   
       wherein:
 the first compressor is a variable speed compressor coupled to a variable speed drive ( 32 ) and the second compressor is a fixed speed compressor; and 
 the second compressor is larger than the first compressor. 
 
     
     
         2 . (canceled) 
     
     
         3 . The system of  claim 1  wherein:
 the second compressor has a larger displacement per revolution than a displacement per revolution of the first compressor. 
 
     
     
         4 . The system of  claim 1  wherein:
 the first compressor and the second compressor are reciprocating compressors. 
 
     
     
         5 . The system of  claim 1  in operational condition with the second compressor connected directly to a line voltage ( 34 ) and the first compressor connected to the line voltage via its variable speed drive. 
     
     
         6 . A transport system ( 200 ) comprising:
 the refrigeration system ( 20 ) of  claim 1 ; and   a refrigerated container ( 201 ) having an interior ( 202 ) containing or in air flow communication with the heat absorption heat exchanger.   
     
     
         7 . (canceled) 
     
     
         8 . The system of  claim 1  wherein:
 a displacement per revolution of the second compressor is 110-350% of a displacement per revolution of the first compressor. 
 
     
     
         9 . The system of  claim 1  wherein:
 the first compressor has an induction motor or a permanent magnet motor; and 
 the second compressor has an induction motor. 
 
     
     
         10 . The system of  claim 1  further comprising a controller configured to:
 at high required capacity (upper range), operate ( 310 ) both the first compressor and the second compressor, the second compressor being operated at a fixed speed; and 
 in low required capacity (lower range), operate ( 318 ) only the first compressor, over at least a portion of said lower capacity range the operating being with variable speed. 
 
     
     
         11 . The system of  claim 10  wherein the controller is configured to in no part of a normal operational range operate the second compressor alone. 
     
     
         12 . A method for operating the system of  claim 1 , the method comprising:
 at high required capacity (upper range), operating ( 310 ) both the first compressor and the second compressor, the second compressor being operated at a fixed speed; and   in low required capacity (lower range), operating ( 318 ) only the first compressor, over at least a portion of said lower capacity range the operating being with variable speed.   
     
     
         13 . The method of  claim 12  wherein:
 the lower range meets the upper range. 
 
     
     
         14 . (canceled) 
     
     
         15 . The method of  claim 12  wherein:
 the operation of the first compressor in an uppermost portion of the lower capacity range is at a power frequency in excess of a line power frequency. 
 
     
     
         16 . The method of  claim 12  wherein:
 a cooldown phase comprises the operation in the high capacity range; and 
 a post-cooldown phase comprises the operation in the lower capacity range. 
 
     
     
         17 . The method of  claim 12  wherein:
 the control is responsive to a sensed air temperature of a controlled space. 
 
     
     
         18 . A method for operating a refrigeration system, the refrigeration system comprising:
 a first compressor ( 24 );   a second compressor ( 26 ) having at least a first condition at least partially in parallel with the first compressor along a refrigerant flowpath;   a heat rejection heat exchanger ( 50 ) downstream of the first compressor and second compressor along the refrigerant flowpath;   an expansion device ( 54 ) downstream of the heat rejection heat exchanger along the refrigerant flowpath; and   a heat absorption heat exchanger ( 56 ) downstream of the expansion device along the refrigerant flowpath,   
       wherein:
 the first compressor is a variable speed compressor coupled to a variable speed drive ( 32 ) and the second compressor is a fixed speed compressor, 
 the method comprising:
 controlling operation of the compressor responsive to a sensed air temperature of the controlled space. 
 
 
     
     
         19 . The method of  claim 18  wherein:
 the sensed air temperature is used to control transitions between operation of only one of the compressors and both of the compressors. 
 
     
     
         20 . A method for operating a refrigeration system, the refrigeration system comprising:
 a first compressor ( 24 );   a second compressor ( 26 ) having at least a first condition at least partially in parallel with the first compressor along a refrigerant flowpath;   a heat rejection heat exchanger ( 50 ) downstream of the first compressor and second compressor along the refrigerant flowpath;   an expansion device ( 54 ) downstream of the heat rejection heat exchanger along the refrigerant flowpath; and   a heat absorption heat exchanger ( 56 ) downstream of the expansion device along the refrigerant flowpath,   
       wherein:
 the first compressor is a variable speed compressor coupled to a variable speed drive ( 32 ) and the second compressor is a fixed speed compressor, 
 the method comprising:
 at high required capacity (upper range), operating ( 310 ) both the first compressor and the second compressor, the second compressor being operated at a fixed speed; and 
 in low required capacity (lower range), operating ( 318 ) only the first compressor, over at least a portion of said lower capacity range the operating being with variable speed, 
 
 
       wherein:
 the lower range comprises a lower sub-range wherein the first compressor is operated in a cyclic mode with essentially fixed speed when operating and, an upper sub-range operated continuously with speed increasing with required capacity. 
 
     
     
         21 . The method of  claim 20  wherein:
 the lower range meets the upper range. 
 
     
     
         22 . The method of  claim 20  wherein:
 the operation of the first compressor in an uppermost portion of the lower capacity range is at a power frequency in excess of a line power frequency. 
 
     
     
         23 . The method of  claim 20  wherein:
 a cooldown phase comprises the operation in the high capacity range; and 
 a post-cooldown phase comprises the operation in the lower capacity range.

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