Batch freezer with cryogenic precooling apparatus and method

Abstract

A freezer for a product includes a housing having a chamber therein with an atmosphere for reducing a temperature of the product; a cryogen refrigeration apparatus operationally associated with the chamber during a first cycle to pre-cool the atmosphere in the chamber; and a mechanical refrigeration apparatus operationally associated with the chamber during a second cycle to cool the atmosphere in the chamber when the first cycle is completed. A process is also provided.

What is claimed is: 
     
         1 . A freezer for a product, comprising:
 a housing having a chamber therein and an atmosphere in said chamber for reducing a temperature of the product;   a cryogen refrigeration apparatus operationally associated with the chamber during a first cycle to pre-cool the atmosphere in the chamber; and   a mechanical refrigeration apparatus operationally associated with the chamber during a second cycle to cool the atmosphere in the chamber when the first cycle is completed.   
     
     
         2 . The freezer of  claim 1 , wherein the cryogen refrigeration apparatus and the mechanical refrigeration apparatus are disposed in the chamber. 
     
     
         3 . The freezer of  claim 1 , wherein the cryogen refrigeration apparatus comprises a pipe extending into the chamber for introducing a cryogen into the atmosphere. 
     
     
         4 . The freezer of  claim 3 , further comprising a manifold connected to the pipe and having at least one outlet for the cryogen. 
     
     
         5 . The freezer of  claim 1 , wherein the mechanical refrigeration apparatus comprises a heat exchanger disposed in the chamber. 
     
     
         6 . The freezer of  claim 1 , further comprising an atmosphere circulation device disposed in the chamber for directing a flow of the atmosphere to contact the mechanical refrigeration apparatus. 
     
     
         7 . The freezer of  claim 6 , wherein the atmosphere circulation device is disposed proximate to the mechanical refrigeration apparatus. 
     
     
         8 . The freezer of  claim 1 , further comprising a shroud disposed in the chamber to direct airflow from the mechanical refrigeration apparatus to the cryogen refrigeration apparatus. 
     
     
         9 . The freezer of  claim 8 , wherein the shroud extends in the chamber from an inner sidewall of the housing to the cryogen refrigeration apparatus. 
     
     
         10 . The freezer of  claim 1 , further comprising:
 a cryogen inlet pipe in fluid communication with the cryogen refrigeration apparatus;   at least one valve in the cryogen inlet pipe for controlling delivery of cryogen through said inlet pipe: and   a controller in electronic communication with the at least one valve for controlling delivery of the cryogen through the cryogen inlet pipe.   
     
     
         11 . The freezer of  claim 10 , further comprising a temperature sensor in communication with the chamber and in electronic communication with the controller for providing a temperature signal to said controller. 
     
     
         12 . A process for reducing a temperature of a product in an atmosphere of a freezer, comprising:
 cryogenically reducing the temperature of the atmosphere with a cryogenic refrigeration apparatus operating during a first cycle for pre-cooling the atmosphere; and   mechanically reducing the temperature of the atmosphere with a mechanical refrigeration apparatus operating during a second cycle for cooling the atmosphere when the first cycle is not operating.   
     
     
         13 . The process of  claim 12 , further comprising suspending the first cycle prior to commencing the second cycle. 
     
     
         14 . The process of  claim 12 , further comprising directing a flow of the atmosphere to contact the mechanical refrigeration apparatus. 
     
     
         15 . The process of  claim 14 , wherein the directing the flow is during the second cycle. 
     
     
         16 . The process of  claim 12 , further comprising sensing a temperature of the atmosphere for determining the operating of the first and second cycles. 
     
     
         17 . The process of  claim 12 , wherein the product comprises a food product. 
     
     
         18 . The process of  claim 12 , wherein the cryogenic refrigeration apparatus comprises a cryogen selected from the group consisting of liquid nitrogen and carbon dioxide.