Process and apparatus for cooling

Abstract

The invention relates to the creation of hybrid refrigeration systems. In one embodiment a low pressure booster circuit is linked to an absorption plant to provide cooling at lower temperatures that can be achieved by the absorption plant alone. The combined systems are efficient compared to vapour compression systems, especially when “waste” heat from other processes is used to drive the absorption part of the circuit. The absorption plant can be provided with heat either by direct firing of a fuel, by waste heat from a combined heat and power (CHP) prime mover (such as a gas engine or gas turbine for example), or by any suitable source of waste heat from another process.

1 . A refrigeration system comprising:
 a compressor arranged to increase the pressure, and thereby increase the temperature, of a vapour of a first refrigerant;   a heat exchanger arranged to remove heat from the first refrigerant to condense the first refrigerant, after the compressor has increased the pressure, and to deliver a liquid of the first refrigerant;   an absorption refrigeration circuit configured to circulate a second refrigerant in an absorption refrigeration cycle, whereby the second refrigerant is cooled, and arranged such that the cooled second refrigerant provides the heat removal duty for the heat exchanger by direct heat exchange with the first refrigerant in the heat exchanger; a pump arranged to increase the pressure of the first refrigerant after heat has been removed from it; and   a first expansion valve arranged to reduce the pressure of the first refrigerant after heat has been removed from the first refrigerant, and to thereby cause flash evaporation of some of the first refrigerant and to reduce the temperature of the first refrigerant to be lower than that of the cooled second refrigerant,   
       wherein the refrigeration system is configured to provide cooling below 0° C. 
     
     
         2 . The system according to  claim 1 , further comprising:
 an evaporator arranged to evaporate the liquid of the first refrigerant received from the first expansion valve, thereby performing a cooling duty and producing a vapour of the first refrigerant, and   wherein the vapour of the first refrigerant from the evaporator is supplied to the compressor.   
     
     
         3 . The system according to  claim 1 , wherein the second refrigerant is water. 
     
     
         4 . The system according to any one of the previous claims, wherein the absorption refrigeration system is arranged to use heat from a combined heat and power plant to drive the absorption refrigeration cycle. 
     
     
         5 . (canceled) 
     
     
         6 . The system according to  claim 1 , wherein the first refrigerant is carbon dioxide. 
     
     
         7 . The system according to  claim 1  further comprising:
 two circuits, each connected to receive first refrigerant from the heat exchanger arranged to cool the first refrigerant and to return the first refrigerant to the compressor arranged to increase the pressure of the first refrigerant; 
 wherein the first expansion valve is located in a first of the two circuits, and a second expansion valve is provided a second of the two circuits. 
 
     
     
         8 . The system according to  claim 7 , wherein the first expansion valve is arrange to cause flash evaporation of some of the first refrigerant and to reduce the temperature of the first refrigerant to a temperature in the range of from 0 to −10° C., and preferably from −4 to −6° C. 
     
     
         9 . The system according to  claim 7 , wherein the second expansion valve is arrange to cause flash evaporation of some of the first refrigerant and to reduce the temperature of the first refrigerant to a temperature in the range of from −20 to −35° C., and preferably from −25 to −30° C. 
     
     
         10 . A method of using the cooling duty provided by an absorption refrigeration system, in a refrigeration system comprising:
 increasing the pressure of a vapour of a first refrigerant, and thereby increasing the temperature of the vapour of the first refrigerant;   removing heat from the first refrigerant after the pressure has been increased, to condense the first refrigerant and thereby delivering a liquid of said first refrigerant;   circulating a second refrigerant in an absorption refrigeration cycle, thereby cooling the second refrigerant;   providing the heat removal duty for the step of removing heat from the first refrigerant via direct heat exchange with the second refrigerant in a heat exchanger;   pumping the first refrigerant to increase its pressure after heat has been removed from it,   reducing the pressure of the first refrigerant after heat has been removed from it, and thereby causing flash evaporation of some of the first refrigerant and reducing the temperature of the first refrigerant to be lower than that of the cooled second refrigerant, and   providing cooling, via the first refrigerant, at below 0° C.   
     
     
         11 . The method according to  claim 10 , further comprising:
 evaporating the first refrigerant after the step of reducing the pressure, to perform a cooling duty and produce a vapour of the first refrigerant.   
     
     
         12 . The method according to  claim 10 , wherein the second refrigerant is water. 
     
     
         13 . The method according to  claim 10 , wherein the absorption refrigeration system is arranged to use heat from a combined heat and power plant to drive the absorption refrigeration cycle. 
     
     
         14 . (canceled) 
     
     
         15 . The method according to  claim 10 , wherein the first refrigerant is carbon dioxide. 
     
     
         16 . The method according to  claim 10 , further comprising:
 circulating the first refrigerant through two circuits, each circuit connected to receive first refrigerant after the step of removing heat from the first refrigerant;   wherein the steps of reducing the pressure and providing the cooling occur for first refrigerant circulated through both of the two circuits.   
     
     
         17 . The method according to  claim 16 , wherein, in the first circuit, the step of reducing the pressure reduces the temperature of the first refrigerant to a temperature in the range of from 0 to −10° C., and preferably from −4 to −6° C. 
     
     
         18 . The method according to  claim 16 , wherein, in the second circuit, the step of reducing the pressure reduces the temperature of the first refrigerant to a temperature in the range of from −20 to −35° C., and preferably from −25 to −30° C. 
     
     
         19 . (canceled)