What is Refrigerator, image.

Refrigerator:

A schematic diagram of the refrigerator is shown in fig. The basic components are

(a). Evaporator

(b). Compressor

(c). Condenser

(d). Expansion device

The evaporator where the refrigerant (working fluid) evaporate absorbing the latent heat of vaporisation is the coldest part of the freezer cabinet, where it is located. In modern frost-free refrigerator, 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 compartment with progressively higher temperatures. The bottom most compartment meant for vegetable is the least cold one. The cold air being heavier flows down from the freezer to the bottom of the refrigerator.

Refrigerator

The warm air being lighter flows upward from the vegetable box to the freezer, gets cold and flow down again. Thus, a neutral convection current is set up which maintains a temperature gradient between the top and bottom of the refrigerator. The temperature maintain in the freezer is about-15℃. The condenser usually a wire and tube type mounted at the back of the refrigerator, having no fan. The refrigerant vapour is condensed with the help of the surrounding air which rises above by 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 evaporate by passing through an expansion device (throttle valve or capillary tube) and the cycle is completed. 

Earlier, the refrigerant used was R-12 and because of the ozone layer depletion it is now isobutene (C4 H10) , propane (C3 H8) or tetrafluoroethane (C2 H2 DE or R-134a).