GB552821A - Improvements in and relating to the desiccation of solutions at low temperatures - Google Patents

Abstract

552,821. Drying solutions by freezing. McFARLANE, A. S. Dec. 18, 1941, No. 16326. [Class 29] In the drying of solutions, such as milk and other food, by freezing followed by evaporation of the ice therefrom under vacuum, the solutions are frozen on to metallic surfaces which are heated by warm refrigerant to assist in the evaporation of the ice without melting it, and the water vapour is condensed as ice on cold surfaces. In the system shown brine or like medium circulated by a pump through a pan P for freezing the solution 6 is cooled by the evaporated 5 of a compression refrigerating machine including a compressor 2, condenser 3 and expansion valve 4. Another machine comprises a compressor 9 and alternative condensers 8 and 18. When the frozen solution is to be heated the compressed gas flows through the condenser 8 in thermal contact with the brine and frozen solution, and through an expansion valve 10 to an evaporator 11 on which the vapour from the ice resolidifies. The refrigerant vapour may return from evaporator 11 direct to the compressor 9 or may first pass through an interchanger coil 13 to assist in cooling the brine. When a fresh charge of solution is to be frozen the compressor 9 delivers to the independent condenser 18, an expansion valve 19 and the coil 13, now serving as the evaporator. In a modification a single compressor is used, and diversion from one condenser and evaporator system to the other is effected by actuation of the valves by a solenoid controlled by a thermal element sensitive to brine temperature. In a further modification, the solution is frozen on to a hollow plate immersed in it in a pan having a jacket traversed by evaporating regrigerant, the plate being cooled by the brine. The compressed gas is condensed in a coil in the brine tank. Specifications 450,145 and 539,477 and U.S.A. Specifications 1,970,956 and 2,066,302 are referred to.