GB1029254A - Method and apparatus for flash freezing - Google Patents

Abstract

1,029,254. Refrigerators. INTEGRAL PROCESS SYSTEMS Inc. Feb. 3, 1965 [Feb. 6, 1964], No. 4699/65. Heading F4H. Freezing apparatus comprises an insulated chamber having a first zone 4a, a second zone 4b, a conveyer 12 for conveying the articles to be frozen from the first to the second zone via a passage 23, nozzles 18 for introducing liquid nitrogen into zone 4a for flash-evaporation therein and a fan 26 for drawing nitrogen vapour through passage 23 and zone 4b. The articles are supplied to the chamber through a tunnel 2 on a conveyer 8 and are removed therefrom through a tunnel 6 on a conveyer 50. Part of the nitrogen vapour from the outlet of fan 26 is returned to zone 4a through ducts 32, 34 and the remainder is supplied through ducts 36, 38 and 40 to the entrance and exit respectively of tunnels 2 and 6 where it forms curtains serving to cool the articles and prevent the ingress of atmospheric air. The rate of flow of liquid nitrogen through a conduit 20 leading to nozzles 18 is regulated by a valve 44 in accordance with the temperature of zone 4b as sensed by an element 42 and the rate of flow of gaseous nitrogen is regulable by dampers 47 in the inlet of fan 26. The chamber and the pipes for the liquid and vaporous nitrogen are double-walled and contain multi-layer polyurethane and aluminium foil insulation which is subjected to a partial vacuum by a pump 54 connected to the walls by conduits 56, 58, 60.