Refrigerant System With Variable Speed Scroll Compressor and Economizer Circuit

Abstract

A scroll compressor system having a variable speed drive is utilized. By providing the economizer and/or bypass functions along with the variable speed drive, precise capacity adjustment between the discrete steps is achieved to exactly match load demands at a wide spectrum of operating conditions.

1 . A refrigerant system comprising:
 at least one scroll compressor having a variable speed drive for varying a speed of said scroll compressor, and said scroll compressor being provided with a suction port, an intermediate pressure port and discharge port;   a condenser downstream of said scroll compressor and an evaporator downstream of said condenser, with an economizer heat exchanger intermediate to said condenser and said evaporator, said economizer heat exchanger selectively returning a tapped refrigerant to said scroll compressor;   at least one condenser fan for moving air across said condenser and at least one evaporator fan for moving air across said evaporator and   a control for selectively operating said economizer heat exchanger to deliver a tapped refrigerant through said economizer heat exchanger, and back to said compressor, and said control also being operable to vary said speed of said scroll compressor to achieve levels of capacity between a level of capacity with said economizer heat exchanger being operational, and a level of capacity without said economizer heat exchanger being operational.   
   
   
       2 . The refrigerant system as set forth in  claim 1 , wherein a bypass port is also provided to selectively bypass refrigerant from said scroll compressor back to a suction line for said scroll compressor, and said control being operable to vary a speed of said scroll compressor to provide levels of capacity between a level of capacity provided when said bypass operation is actuated, and without said bypass operation being actuated. 
   
   
       3 . The refrigerant system as set forth in  claim 2 , wherein said bypass port and said intermediate pressure port are provided by the same port. 
   
   
       4 . The refrigerant system as set forth in  claim 2 , wherein the delivery of said bypass refrigerant is controlled by a flow control device. 
   
   
       5 . The refrigerant system as set forth in  claim 2 , wherein said scroll compressor is a single stage compressor, and said intermediate pressure port within said scroll compressor also communicates with said bypass port. 
   
   
       6 . The refrigerant system as set forth in  claim 2 , wherein said scroll compressor has at least two scroll compressor stages, and said intermediate pressure port is between two of said stages. 
   
   
       7 . The refrigerant system as set forth in  claim 2 , wherein said control changing said speed of said scroll compressor in incremental steps. 
   
   
       8 . The refrigerant system as set forth in  claim 2 , wherein said bypass port selectively communicates an intermediate pressure line receiving said tapped refrigerant back to a suction line leading to said compressor. 
   
   
       9 . The refrigerant system as set forth in  claim 2 , wherein said bypass is between a discharge line for compressed refrigerant, and back to the suction line. 
   
   
       10 . The refrigerant system as set forth in  claim 1 , wherein said tapped refrigerant is returned to said intermediate compression port 
   
   
       11 . The refrigerant system as set forth in  claim 1 , wherein the delivery of said tapped refrigerant is controlled by a flow control device. 
   
   
       12 . The refrigerant system as set forth in  claim 1 , wherein said system is part of a refrigeration transportation unit. 
   
   
       13 . The refrigerant system as set forth in  claim 12 , wherein said refrigeration transportation unit is a refrigeration container unit. 
   
   
       14 . The refrigerant system as set forth in  claim 12 , wherein said refrigeration transportation unit is a tractor/trailer unit. 
   
   
       15 . The refrigerant system as set forth in  claim 1 , wherein at least one said evaporator fans having a variable speed drive for varying a speed of said fan 
   
   
       16 . The refrigerant system as set forth in  claim 1 , wherein at least one said condenser fans having a variable speed drive for varying a speed of said fan 
   
   
       17 . The refrigerant system as set forth in  claim 1 , wherein there is a suction modulation valve located downstream of said evaporator. 
   
   
       18 . The refrigerant system as set forth in  claim 1 , wherein said scroll compressor is a single stage compressor. 
   
   
       19 . The refrigerant system as set forth in  claim 1 , wherein said scroll compressor has at least two stages. 
   
   
       20 . The refrigerant system as set forth in  claim 1 , wherein said control changing said speed of said scroll compressor in incremental steps. 
   
   
       21 . The refrigerant system as set forth in  claim 1 , wherein said scroll compressor has at least two scroll compressor stages, and said intermediate pressure port is between said two stages. 
   
   
       22 . The refrigerant system as set forth in  claim 21 , wherein there are more than two scroll compressor stages, with said intermediate pressure port being between two of said stages. 
   
   
       23 . The refrigerant system as set forth in  claim 21 , wherein a variable speed drive controls both of said two scroll compressor stages. 
   
   
       24 . The refrigerant system as set forth in  claim 21 , wherein at least one of said two scroll compressor stages does not have a variable speed drive. 
   
   
       25 . A method of operating a refrigerant system having a scroll compressor, and an economizer cycle, along with a variable speed drive for said compressor;
 determining a desired load on said refrigerant system, and determining whether said economizer cycle should be engaged to meet said desired load; and   varying a speed of said scroll compressor to meet said desired load.   
   
   
       26 . The method as set forth in  claim 25 , wherein said scroll compressor is further provided with an unloader function, and both said unloader and said economizer providing modes being used to meet said desired load. 
   
   
       27 . The method as set forth in  claim 25 , wherein said speed of said scroll compressor is varied in incremental steps. 
   
   
       28 . The method as set forth in  claim 25 , wherein a suction modulation valve is also provided, and is actuated to vary the operational function of the refrigerant system to meet said desired load.