Refrigeration system with bypass subcooling and component size de-optimization

Abstract

A refrigeration system having a primary refrigerant path including a compressor, a condenser, a primary expansion device, and an evaporator connected together to form a closed loop system with a refrigerant circulating therein; and a bypass path coupled to an outlet of the condenser. The bypass path includes a secondary expansion device; and a heat exchanger thermally coupled to the primary refrigerant path between the condenser outlet and the primary expansion device inlet to remove heat from the refrigerant discharged from the condenser. The condenser is downsized such that lacks the heat transfer capacity to provide some or all of the required subcooling as provided according to conventional practice, and the heat exchanger provides some or all the required subcooling according to the capacity of the condenser. A pressure differential accommodating device operative to mix two vapors at different pressures may also be provided to connect the outlets of the evaporator and the heat exchanger to an inlet of the compressor. A method of operating a refrigeration system with a downsized condenser and an a bypass path including a heat exchanger to provide subcooling is also described.

1 - 80 . (canceled)  
   
   
       81 . A refrigeration system comprising: 
 a primary refrigerant path including a compressor, a condenser, a primary expansion device, and    an evaporator connected together to form a closed loop system with a refrigerant circulating therein; and    a bypass path attached between the outlet of the condenser and the inlet of the compressor, the bypass path including: 
 a secondary expansion device; and  
 a heat exchanger thermally coupled to the primary refrigerant path between the condenser outlet and the primary expansion device inlet which provides subcooling of the refrigerant discharged from the condenser, the heat transfer capacity of the condenser being insufficient to provide the required subcooling.  
   
   
   
       82 . A refrigeration system according to  claim 81 , wherein the heat exchanger and the condenser are so constructed that the required subcooling is provided substantially entirely by the heat exchanger.  
   
   
       83 . A refrigeration system according to  claim 81 , wherein the heat exchanger and the condenser are so constructed that a majority of the subcooling of the refrigerant is provided by the heat exchanger.  
   
   
       84 . A refrigeration system according to  claim 81 , wherein: 
 the vapor pressure of the refrigerant exiting the heat exchanger is higher than that of the refrigerant exiting the evaporator, and    the system further includes a pressure differential accommodating device connecting the outlets of the evaporator and the heat exchanger to an inlet of the compressor.    
   
   
       85 . A refrigeration system according to  claim 84 , further including a valve in the bypass path, the valve being operable to divert about 5% to about 15% of the refrigerant to the bypass path when maximum cooling capacity is required due to high thermal load, and to divert up to about 60% of the refrigerant to the bypass path according to reductions in thermal load.  
   
   
       86 . A refrigeration system according to  claim 84 , wherein the pressure differential accommodating device is a vacuum generating device having inlets connected to outlets of the evaporator and the heat exchanger and an outlet connected to the inlet of the compressor, or a pressure reducing device connected to the outlet of the heat exchanger, and a mixing device connecting the pressure reducing device and the outlet of the evaporator to the inlet of the compressor.  
   
   
       87 . A refrigeration system according to  claim 86 , wherein the vacuum generating device is a vortex tube or a venturi tube, and the pressure reducing device is a capillary tube, a restricted orifice, a valve, or a porous plug.  
   
   
       88 . A refrigeration system according to  claim 81 , wherein the bypass path is connected to the outlet of the condenser downstream of the heat exchanger.  
   
   
       89 . A refrigeration system according to  claim 81 , wherein: 
 the evaporator is comprised of a plurality of parallel-connected evaporator elements located in respective portions of the space being cooled by the system; and    the system further includes a plurality of on-off valves respectively connecting the primary expansion device to the evaporator elements, the on-off valves being operable to idle respective evaporator elements by shutting of the flow of refrigerant thereto when cooling of a particular location is not required at given time; and    an adjustable valve in the bypass path, the adjustable valve being operative to control the flow of refrigerant in the bypass path such that refrigerant mass flow which is not required in the primary refrigerant path when a particular evaporator element is idle flows to the bypass path.    
   
   
       90 . A refrigeration system according to  claim 89 , wherein the compressor is configured and controlled to run continuously when the system is in operation, independent of changes in thermal load.  
   
   
       91 . A refrigeration system according to  claim 89 , wherein the condenser is downsized from that conventionally required for an evaporator selected to achieve a desired cooling capacity.  
   
   
       92 . A refrigeration system according to  claim 91 , wherein the evaporator is oversized from that conventionally required to increase cooling capacity without increasing compressor work  
   
   
       93 . A refrigeration system according to  claim 89 , further including a pressure differential accommodating device having a low pressure inlet connected in common to outlets of the evaporator elements, a high pressure input connected to the bypass path, and an outlet connected to an inlet of the compressor.  
   
   
       94 . A refrigeration system according to  claim 89 , wherein the valve in the bypass path is operable to divert about 5% to about 15% of the refrigerant to the bypass path when maximum cooling capacity is required due to operation of all the evaporator elements, and to divert up to about 60% of the refrigerant to the bypass path according to reductions in thermal load due to deactivation of particular evaporator elements.  
   
   
       95 . A refrigeration system according to  claim 81 , further including a valve in the bypass path, the valve being operable to divert about 5% to about 15% of the refrigerant to the bypass path when maximum cooling capacity is required due to high thermal load, and to divert up to about 60% of the refrigerant to the bypass path according to reductions in thermal load.  
   
   
       96 . A refrigeration system according to  claim 81 , wherein the compressor is configured and controlled to run continuously when the system is in operation, independent of changes in thermal load.  
   
   
       97 . A refrigeration system according to  claim 81 , wherein the expansion device in the primary refrigeration path is thermostatically operated in response to a temperature sensor thermally coupled to the inlet of the compressor to maintain a constant superheat in the evaporator.  
   
   
       98 . A refrigeration system according to  claim 81 , wherein the condenser is downsized from that conventionally required for an evaporator selected to achieve a desired cooling capacity.  
   
   
       99 . A refrigeration system according to  claim 98 , wherein the compressor is configured and controlled to run continuously when the system is in operation, independent of changes in thermal load.  
   
   
       100 . A refrigeration system according to  claim 98 , wherein the evaporator is oversized from that conventionally required to increase cooling capacity without increasing compressor work  
   
   
       101 . A refrigeration system according to  claim 81 , wherein the heat exchanger is connected to provide counter-flow of refrigerant in the heat exchanger and the thermally coupled refrigerant in the primary refrigerant path.  
   
   
       102 . A refrigeration system according to  claim 81 , wherein the refrigerant circulated in the system consists of a single component.  
   
   
       103 . A refrigeration system according to  claim 81 , wherein the refrigerant circulated in the system is a mixed-refrigerant comprising a plurality of components selected to provide a desired combination of thermal and flammability characteristics.  
   
   
       104 . A refrigeration system according to  claim 103 , further including a liquid-vapor separator operable to selectively divert at least one component of the mixed refrigerant to the bypass path to increase the percentage of liquid in the refrigerant as it enters the evaporator, thereby improving evaporator efficiency.  
   
   
       105 . A refrigeration system according to  claim 104 , wherein the diverted refrigerant component has a higher condensation temperature and boiling temperature than the remainder of the refrigerant components.  
   
   
       106 . A method of increasing the efficiency of a refrigeration system comprising the steps of: 
 passing refrigerant through a primary refrigerant path which includes a compressor, a condenser, a primary expansion device, and an evaporator connected together to form a closed loop system wherein the heat transfer capacity of the condenser is insufficient to provide required subcooling for the circulating refrigerant;    diverting a portion of the refrigerant exiting the condenser into a secondary refrigerant path which includes a secondary expansion device and a heat exchanger thermally coupled to the primary refrigerant path between the condenser outlet and the primary expansion device inlet; and    passing the diverted refrigerant through the heat exchanger to provide subcooling for refrigerant flowing in the primary refrigerant path.    
   
   
       107 . A method according to  claim 106 , further including the steps of: 
 passing the refrigerant exiting the heat exchanger and the refrigerant exiting the evaporator through a pressure differential accommodating device that mixes two vapors at different pressures; and    delivering the refrigerant exiting the pressure differential accommodating device to an inlet of the compressor.    
   
   
       108 . A method according to  claim 106 , wherein the refrigerant is diverted to the bypass path at a location downstream of the heat exchanger.  
   
   
       109 . A method according to  claim 106 , wherein substantially all of the subcooling required is provided by heat transfer in the heat exchanger.  
   
   
       110 . A method according to  claim 106 , wherein a majority of the subcooling required is provided by heat transfer in the heat exchanger.  
   
   
       111 . A method according to  claim 106 , wherein between about 5% and about 15% of the liquid refrigerant outflow from the condenser is diverted to the bypass path.  
   
   
       112 . A method according to  claim 106 , further including the step of: 
 controlling the quantity of refrigerant outflow from the condenser which is diverted to the bypass path to adjust the cooling capacity of the system according to the thermal load.    
   
   
       113 . A method according to  claim 112 , further including the step of running the compressor continuously independent of the required cooling capacity when the system is in operation.  
   
   
       114 . A method according to  claim 106 , wherein: 
 the primary refrigeration path includes a plurality of evaporators located in respective locations to be separately cooled; and the method further includes the steps of:    diverting a predetermined minimum quantity of refrigerant to the bypass path when maximum cooling capacity is required to cool all of the locations; and    diverting increasing quantities of refrigerant to the bypass path as thermal load decreases.    
   
   
       115 . A method according to  claim 114 , further including the step of running the compressor continuously independent of the required cooling capacity when the system is in operation.  
   
   
       116 . A method according to  claim 114 , wherein the condenser is downsized from that conventionally required for an evaporator selected to achieve a desired cooling capacity.  
   
   
       117 . A method according to  claim 116 , wherein the evaporator is oversized from that conventionally required to increase cooling capacity without increasing compressor work.  
   
   
       118 . A method according to  claim 114 , further including the steps of: 
 idling particular evaporators in locations which do not require cooling at a given time by blocking the flow of refrigerant thereto;    diverting the refrigerant normally delivered to a particular evaporator to the bypass path what that evaporator is idle.    
   
   
       119 . A method according to  claim 106 , wherein the refrigerant circulated in the system consists of a single component.  
   
   
       120 . A method according to  claim 106 , wherein the refrigerant circulated in the system is a mixed-refrigerant comprising a plurality of components selected to provide a desired combination of thermal and flammability characteristics.  
   
   
       121 . A method according to  claim 120 , further including the step of selectively diverting at least one component of the mixed refrigerant to the bypass path to increase the percentage of liquid in the refrigerant as it enters the evaporator, thereby improving evaporator efficiency.  
   
   
       122 . A method according to  claim 121 , wherein the diverted refrigerant has a high condensation temperature and a high boiling temperature relative to the remainder of the refrigerant.  
   
   
       123 . A method according to  claim 106 , further including the steps of: 
 sensing the temperature of the refrigerant at the inlet of the compressor; and    controlling the mass flow rate of refrigerant through the expansion device in the primary refrigeration path according to the sensed temperature to maintain the superheat of the refrigerant exiting the evaporator at a constant level.    
   
   
       124 . A method according to  claim 106 , wherein the condenser is downsized from that conventionally required for an evaporator selected to achieve a desired cooling capacity.  
   
   
       125 . A method according to  claim 124 , wherein the evaporator is oversized from that conventionally required to increase cooling capacity without increasing compressor work.  
   
   
       126 . A method according to  claim 106 , further including the step of running the compressor continuously independent of the required cooling capacity when the system is in operation.