Method and apparatus for impingement freezing of irregularly shaped products

Abstract

An impinger for cooling or freezing products includes an impingement plate containing openings for directing impingement jets of a mixture of gas and solid or liquid cryogen toward the products transported on a conveyor, wherein the openings in aggregate have an open area of about 7% to about 12% of the total surface area of the impingement plate, the impingement plate providing a back pressure restriction of about 220 to about 475 Pa. A process for cooling or freezing products within a housing chamber includes transporting the products, particularly IQF food products, on a moving substrate within the chamber, mixing a gas with solid or liquid cryogen to form a mixture, directing the mixture to the aforementioned impinger; and selectively directing the pressurized impingement jets of the mixture from the impingement plate toward the products transported on the substrate.

What is claimed is: 
     
         1 . An impinger for cooling or freezing products, comprising:
 an impingement plate containing openings for directing impingement jets of a mixture of gas and solid or liquid cryogen toward the products transported on a conveyor,   wherein the openings comprise an open area in aggregate of about 7 percent to about 12 percent of the total surface area of the impingement plate, and   wherein the impingement plate provides a back pressure restriction in a circulation path of the mixture of about 220 to about 475 Pa.   
     
     
         2 . The impinger of  claim 1 , wherein the impingement plate provides a back pressure restriction in a circulation path of the mixture of about 270 to about 475 Pa. 
     
     
         3 . The impinger of  claim 1 , wherein an impingement velocity of the mixture through the openings is about 13.7 meters per second to about 17.8 meters per second. 
     
     
         4 . The impinger of  claim 1 , wherein an impingement velocity of the mixture through the openings is about 16.2 meters per second to about 17.8 meters per second. 
     
     
         5 . The impinger of  claim 1 , wherein a cross-sectional area of the openings is within a range of about 2.8 cm 2  to about 20.5 cm 2 . 
     
     
         6 . The impinger of  claim 1 , wherein each of the openings is a substantially circular hole having a diameter in a range of about 1.9 to about 5.1 centimeters. 
     
     
         7 . The impinger of  claim 1 , wherein each of the openings is a substantially circular hole having diameters in a range of about 2.5 to about 3.8 centimeters. 
     
     
         8 . The impinger of  claim 1 , wherein the openings are punched holes or chamfered holes. 
     
     
         9 . The impinger of  claim 1 , further comprising a vibrator mounted for co-action with the impingement plate. 
     
     
         10 . A process for cooling or freezing products within a housing chamber, comprising:
 transporting the products on a moving substrate within the chamber;   mixing a gas with solid or liquid cryogen to form a mixture;   directing the mixture of gas and solid or liquid cryogen to an impinger, the impinger comprising an impingement plate containing openings for providing pressurized impingement jets of the mixture, wherein the openings comprise in aggregate an open area of about 7 percent to about 12 percent of the total surface area of the impingement plate, and wherein the impingement plate provides a back pressure restriction in a circulation path of the mixture of about 220 to about 475 Pa; and   selectively directing the pressurized impingement jets of the mixture from the impingement plate toward the products transported on the substrate.   
     
     
         11 . The process of  claim 10 , wherein the products comprise individually quick frozen (IQF) products. 
     
     
         12 . The process of  claim 10 , wherein an impingement jet velocity of the mixture through the openings is about 13.7 meters per second to about 17.8 meters per second. 
     
     
         13 . The process of  claim 10 , wherein an impingement velocity of the mixture through the openings is about 16.2 meters per second to about 17.8 meters per second. 
     
     
         14 . The process of  claim 10 , wherein a cross-sectional area of the openings is within a range of about 2.8 cm 2  to about 20.5 cm 2 . 
     
     
         15 . The process of  claim 10 , wherein each of the openings is a substantially circular hole having a diameter in a range of about 1.9 to about 5.1 centimeters. 
     
     
         16 . The process of  claim 10 , wherein said mixing of the gas with solid or liquid cryogen occurs at least partially within an at least partially enclosed impingement hood above the substrate, the impingement hood comprising a shell supporting the impinger, the shell being adapted to accommodate a gas circulation device for directing the mixture of gas and solid or liquid cryogen to the impinger. 
     
     
         17 . The process of  claim 10 , wherein the housing chamber comprises a plurality of attached modular enclosures; the process including spraying liquid cryogen in at least one enclosure near the products to form the mixture; circulating the mixture from a low pressure area to create a high pressure area above and below the substrate in each enclosure; directing the mixture through the impinger impingement plate to generate the impingement jets in each enclosure; impinging the products with the impingement jets in each enclosure; and recirculating the mixture to the low pressure area in each enclosure. 
     
     
         18 . The process of  claim 10 , further comprising re-circulating the mixture of gas and the cryogen into the impinger after impingement onto the products. 
     
     
         19 . A method for increasing heat transfer to individually quick frozen (IQF) products in an impingement freezer, comprising at least one of installing and retrofitting the impinger of  claim 1  as at least one impinger in the freezer.