Cryogenic Cooling Method and Installation Using Liquid CO2 and Employing Two Exchangers in Series

Abstract

A method and installation using liquid CO 2 as a cryogenic fluid for transferring cold energy to products, wherein liquid CO 2 is sent into a heat exchanger system including first and second heat exchangers connected in series. The liquid CO2 is supplied to the first heat exchanger where it evaporates. Gaseous CO2 from the first exchanger is supplied to the second heat exchanger. The atmosphere surrounding the products is blown across the heat exchangers to provide a cooled atmosphere with which to cool the products. The latent heat of vaporization of the liquid CO2 in the first heat exchanger and the sensible heat of the gaseous CO2 in the second heat exchanger satisfies the cooling requirement of the products. The first exchanger is kept at a pressure higher than the triple point pressure for CO 2 , whereas the second exchanger is held at atmospheric pressure or at a pressure between the triple point of the fluid and atmospheric pressure.

1 - 9 . (canceled) 
     
     
         10 . A process for indirectly cooling products using liquid CO 2 , comprising the steps of:
 supplying liquid CO 2  to a heat exchanging system at which the liquid CO 2  evaporates, the heat exchanging system comprising first and second heat exchangers connected in series, the first heat exchanger being kept at a pressure above the triple point pressure of CO 2 , the second heat exchanger being kept at atmospheric pressure or at a pressure between the triple point pressure of CO 2  and atmospheric pressure; and   removing heat from the products through heat exchange between cold walls of the heat exchangers and an atmosphere surrounding the products.   
     
     
         11 . The process of  claim 10 , further comprising:
 adjusting a flow rate of the liquid CO 2  supplied to the first heat exchanger with a liquid CO 2  flow rate adjustment element disposed upstream of the first heat exchanger, the adjustment being based upon a cooling requirement of the products to be cooled, the liquid CO 2  flow rate adjustment element comprising either a thermostatic regulator or a temperature probe/regulator/valve assembly;   maintaining a pressure in the first heat exchanger above the triple point pressure of CO 2 ; and   transferring gaseous CO 2 , formed from vaporization of the liquid CO 2  in the first heat exchanger, to the second heat exchanger   
     
     
         12 . The process of  claim 11 , wherein the pressure in the first heat exchanger is kept at a pressure above the triple point pressure of CO 2  by virtue of a back-pressure regulation device that is placed at an outlet of the first heat exchanger, the back-pressure regulation device comprising either a back-pressure regulator or a pressure sensor/regulator/valve assembly. 
     
     
         13 . The process of  claim 12 , wherein a phase separator is disposed in fluid communication between the outlet of the first heat exchanger and the back-pressure regulation device, the phase separator preventing liquid CO 2  from flowing into the second heat exchanger. 
     
     
         14 . An installation for cooling products using liquid CO 2 , comprising, a first heat exchanger receiving liquid CO 2 , a second heat exchanger receiving gaseous CO 2  formed from vaporization of the liquid CO 2  in the first heat exchanger, a blower operatively associated with the first and second heat exchangers, a liquid CO 2  flow rate adjustment element disposed upstream of the first heat exchanger, and a back-pressure regulation device, wherein:
 the liquid CO 2  flow rate adjustment element is adapted and configured to adjust a flow rate of liquid CO 2  into the first heat exchanger based upon a cooling requirement of the products to be cooled and comprises either a thermostatic regulator or a temperature probe/regulator/valve assembly;   the blower is adapted and configured to blow an atmosphere surrounding the products to be cooled into contact with cold walls of the heat exchange system;   the first and second heat exchangers are connected in series;   the back-pressure regulation device is disposed downstream of an outlet of the first heat exchanger and is adapted and configured to maintain a pressure in the first heat exchanger above the triple point pressure of CO 2 .   
     
     
         15 . The installation of  claim 14 , further comprising a phase separator inserted upstream of the back-pressure regulation device. 
     
     
         16 . The installation of  claim 14 , wherein the back-pressure regulation device comprises either a back-pressure regulator or a pressure sensor/regulator/valve assembly.