In the present work, a plate freezer consisting of two plates connected inparallel and having a cooling load of 0.335 KW is to be designed. Installing formedtubing between two metal plates, which are brazed together at the edges, forms theplate surface evaporators.The refrigerant used is R-134a a refrigerant which is now used as areplacement for R-12.
Conventional food preservation is done by keeping the food inside chambershaving evaporator coils around it. This chamber is insulated from the surroundings by acasing. The vapour compression system is the most widely used system.

The heat transfer takes place from the food to the freezer (chamber) surfacethrough the air gap. As air is a bad conductor of heat, the freezing rate is low and time consuming. The freezing rate was increased by the development of the freezer. Onlycompactable foods can utilize this method.

The Plate freezer under consideration is a multi plate freezer. In the plate freezer there are two plates through which the refrigerant expands. The food is placed betweenthe plates and are brought closer so that the food gets pressed to a pre-determined pressure. As the plates are in direct contact with the food, there is better heat transfer andhence the freezing rate is increased. 

The plate used is copper plate, which is having a high heat transfer coefficient.The two plates are brought closer manually.

Compared to the conventional method of freezing this method takes only aQuarter of the time required to bring 1 kg of meat from 30 ºC to -20 ºC, the freezing rateis increased about four times. This is the most important reason why plate freezers arereplacing conventional freezing equipments in the recent past.

The Carnot cycle is the model of perfection for a refrigeration cycle. However, itis not practicable to realize this perfect thermodynamic cycle with hardware. Firstly, twocompression machines, one realizing isentropic compression, the other realizingisothermal compression would be required. Secondly, the small amount of expansionwork available does not support the idea of incorporating a work producing expander intothe system. The Carnot cycle is shown for a refrigerator. Heat is delivered isothermally atTH and received.

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