Method and apparatus for freezing products

Abstract

A method of freezing a product, which method comprises the steps of vaporizing a cryogenic liquid and warming the vapor thus formed with a product to be frozen, characterized by using the warmed vapor thus obtained to cool compressed gaseous refrigerant in a mechanical refrigeration system before expansion thereof.

1 . A method of freezing a product, which method comprises the steps of: 
 (a) vaporising a cryogenic liquid and warming the vapour thus formed with a product to be frozen without passing the vapour through a work expander; and    (b) using the warmed vapour thus obtained to cool compressed refrigerant in a mechanical refrigeration system before expansion thereof.    
     
     
         2 . A method according to  claim 1 , wherein said cryogenic liquid is liquid nitrogen.  
     
     
         3 . A method according to  claim 1 , wherein the vapour is brought into direct heat exchange with said product to refrigerate the same.  
     
     
         4 . A method according to  claim 1 , wherein the vapour is brought into indirect heat exchange with said product to refrigerate the same.  
     
     
         5 . A method according to  claim 1 , wherein, said mechanical refrigeration system has a refrigerated space and said method includes the step of passing said product through said refrigerated space after freezing at least the surface thereof with cryogenic fluid.  
     
     
         6 . A method according to  claim 1 , wherein said mechanical refrigeration system has a refrigerated space and said method includes the step of passing said product through said refrigerated space before freezing it with cryogenic fluid.  
     
     
         7 . A method as claimed in  claim 1 , wherein said product is a foodstuff.  
     
     
         8 . An apparatus for freezing a product, which apparatus comprises: 
 (a) a freezer adapted to be cooled by a cryogenic fluid without a work expander;    (b) a mechanical refrigeration system having: 
 (i) a compressor; and  
 (ii) means for expanding said compressed refrigerant,  
   wherein said apparatus further comprises means for conveying cryogenic fluid from said freezer to a heat exchanger to, in use, cool compressed refrigerant prior to expansion thereof.    
     
     
         9 . An apparatus as claimed in  claim 8 , wherein said mechanical refrigerator comprises a refrigerated space.  
     
     
         10 . An apparatus as claimed in  claim 9 , wherein said refrigerated space is disposed downstream of said freezer.  
     
     
         11 . An apparatus as claimed in  claim 9 , wherein said refrigerated space is disposed upstream of said freezer.