Refrigerators are applicable for food preservation at the end user level. A refrigerator is an insulated box in which lower temperature is maintained to facilitate short or medium term storage of food. The refrigerator is usually specified as per volumetric capacity on the inside. Hence, it is available in single door capacities of 65 litre, 100 litre, 165 litre, 175 litre to double door refrigerator of capacities as large as 1000 litre.Large size refrigerators come with independent compartments as per food category. So, we get freezer cabinet, vegetable pull out compartment and so on.
Most of the refrigerators come with painted steel sheet cabinet on the outside with strong industrial plastic inner cabinet for rust proofness.
In early refrigerator’s cork, expanded polystyrene (thermocol) sheets or granules were used for insulation. But nowadays poly urethane foam (PUF) is the most common insulation used in the refrigerators. The door of the cabinet is provided with neoprene rubber gasket to prevent leakage of air from the cabinet.
The inner cabinet and the inner panel of door is suitably formed to provide trays for different categories of food.In smaller refrigerator upto 165 litre the circulation of air for cooling is by natural convection.
This allows a range of temperature from 20°C in the freezer cabinet at the top to about 5°C in the vegetable tray located at the bottom. The trays are not solid to allow air flow through the trays for circulation of air.The temperature is maintained within a range by cyclic control. The compressor acts off at lower end i.e. cut off temperature and restarts at higher end i.e. cut in temperature.
