Cooling systems

Abstract

An apparatus has a compressor having suction and discharge ports. One or more conduits form a main flowpath from the discharge port through a condenser, a heat exchanger first leg, a first expansion device, and an evaporator to return to the suction port. The conduits also form a bypass flowpath bypassing the heat exchanger first leg, the first expansion device, and the evaporator but passing through a second leg of the heat exchanger in heat exchange relation with the first leg.

1 . An apparatus comprising: 
 a compressor having suction and discharge ports;    a condenser;    a first expansion device;    a second expansion device;    an evaporator;    a heat exchanger having first and second portions in heat exchange relation with each other; and    one or more conduits forming: 
 a main flowpath from the discharge port through the condenser, the heat exchanger first portion, the first expansion device, and the evaporator and returning to the suction port; and  
 a bypass flowpath bypassing the heat exchanger first portion, the first expansion device, and the evaporator, but passing through the second expansion device and the heat exchanger second portion.  
   
   
   
       2 . The apparatus of  claim 1  wherein: 
 the evaporator lacks a distributor.    
   
   
       3 . The apparatus of  claim 1  wherein: 
 the second expansion device is a TXV having a bulb essentially in heat exchange relation with a suction port condition.    
   
   
       4 . The apparatus of  claim 1  wherein: 
 the second expansion device is an EXV.    
   
   
       5 . The apparatus of  claim 4  further comprising: 
 a controller coupled to the EXV and programmed to control the EXV responsive to indicated superheat.    
   
   
       6 . The apparatus of  claim 1  wherein: 
 the heat exchanger first portion is downstream of the condenser and upstream of the evaporator along the main flowpath; and    the heat exchanger second portion is downstream of the condenser along the bypass flowpath.    
   
   
       7 . The apparatus of  claim 6  wherein: 
 the heat exchanger first portion is upstream of the first expansion device along the main flowpath.    
   
   
       8 . The apparatus of  claim 1  wherein: 
 the evaporator is a refrigerant-to-air heat exchanger.    
   
   
       9 . The apparatus of  claim 1  wherein: 
 in at least a bypass mode, a bypass flow along the bypass flowpath enters the heat exchanger second portion in a two-phase gas/liquid condition and exits the heat exchanger second portion in a single-phase superheated gas condition; and    in the bypass mode, a main flow along the main flowpath remains essentially a single-phase liquid in said heat exchanger second portion.    
   
   
       10 . The apparatus of  claim 1  wherein: 
 the compressor is selected from the group consisting of screw compressors and scroll compressors.    
   
   
       11 . A method for operating the apparatus of  claim 1  comprising: 
 detecting at least one operational parameter; and    responsive to the detecting, operating at least the second expansion device so as to maintain essentially single-phase liquid refrigerant entering the evaporator along the main flowpath.    
   
   
       12 . The method of  claim 11  wherein: 
 the at least one operational parameter includes at least one of: 
 saturated suction temperature; and  
 actual suction temperature.  
   
   
   
       13 . A method for operating a cooling system comprising: 
 causing a main flow of refrigerant through an evaporator; and    precooling the main flow upstream of the evaporator so as to so as to maintain said main flow essentially as a liquid entering the evaporator.    
   
   
       14 . The method of  claim 13  wherein: 
 the precooling comprises controlling a bypass flow in heat exchange relation with the main flow.    
   
   
       15 . The method of  claim 13  further comprising: 
 determining whether, absent the precooling, the main flow would enter the evaporator essentially as a two-phase flow.    
   
   
       16 . The method of  claim 15  wherein: 
 the determining includes determining that a superheat of refrigerant exiting the evaporator exceeds a threshold.    
   
   
       17 . A system comprising: 
 a compressor;    a condenser;    a discharge line, coupling the compressor to the condenser to carry at least a main flow of refrigerant from the compressor to the condenser;    an expansion device;    an evaporator;    a suction line, coupling the evaporator to the compressor to carry refrigerant from the condenser to the compressor and comprising a first and second parallel segments; and    means for precooling refrigerant entering the expansion device so as to maintain said main flow essentially as a liquid while flowing along a flowpath length at least from the expansion device to the evaporator.    
   
   
       18 . The system of  claim 17  wherein: 
 the evaporator lacks a distributor.    
   
   
       19 . The system of  claim 17  wherein: 
 within the evaporator, the main flow transitions to a two-phase liquid/gas flow and then to a one-phase superheated gas flow.    
   
   
       20 . The system of  claim 17  wherein: 
 the bypass flow represents 10%-35%, by weight, of a total refrigerant flow through the compressor.