Working of Domestic Refrigerator

The basic components are,

a) Evaporator

b) Compressor

c) Condenser

d) Expansion Device

The evaporator where the refrigerant (working fluid) evaporates absorbing the latent heat of vaporization is the coldest part of the freezer cabinet, where it is located. In modern frost-free refrigerators, the evaporator is located outside the cabinet. A fan circulates air from the evaporator to the freezer. Just below the freezer, there is a chiller tray. Further below are compartments with the progressively higher temperatures. The Bottom-most compartment meant for vegetables is the least cold one. The cold air being heavier flows down from the freezer to the bottom of the refrigerator. The warm air being lighter flows upward from the vegetable box to the freezer, gets cooled and flows down again. Thus, a natural convection current is set up which maintains a temperature gradient between the top and bottom of the refrigerator. The temperature maintained in the freezer is about -15*C. The condenser is usually a wire - and - tube type mounted at back of the refrigerator, having no fan. The refrigerant vapor is condensed with the help of the surrounding air which rises above the natural convection as it gets heated after absorbing the latent heat of condensation from the refrigerant. After condensation, the high pressure liquid refrigerant is reduced to the low pressure of the evaporator by passing through an expansion device ( throttle valve or capillary tube ) and cycle is completed.

Earlier, the refrigerant used was R-12 and because of the ozone layer depletion it is now isobutene ( C3H10 ), propane ( C3H8 ) or Tetrafluoroethene ( C2H2f4 or R-134a).

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