Importance

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Abstract

An endless conveyor carries articles being cooled through a freezing tunnel. Spray nozzles at longitudinally spaced locations along the tunnel expand high pressure liquid nitrogen to substantially atmospheric pressure to create a central flow of cold fluid in association with a surrounding inducer. The nozzles are arranged in an array with a first group being directed downward and toward the entrance and with a second group being directed downward and toward the exit end. A fan disposed in the intermediate region between the two groups creates an upward flow of cryogen vapor into the region that maintains a head of higher pressure vapor at the entrance to each of the inducers. Downwardly directed blowers are located between the array and both the entrance and exit ends in order to assure there is efficient extraction of heat from articles being carried along the conveyor from end to end. The inducers create an efficient circulation of vapor in the enclosure, and the rate of flow of cryogen being expanded is regulated by using nozzles having changeable orifice areas.

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First Claim