What happens when we place hot coffee on a table ? As time passes, the temperature of coffee reduces so that it is equal to the surrounding temperature in which it is placed. The same mechanism is applied in refrigerators. The continuous flow of cold substance in refrigerators makes it a ‘surrounding of low temperature’ that it cools the object placed in it. So how to create this continuous flow ? A refrigerant ( Why not any other substance ? Refrigerant is a substance that can easily undergo phase transition) is passed through a compressor and its pressure is increased. As pressure increases, the temperature also raises due to decrease in volume. This superheated high pressure vapour is passed into the condenser coils( the zig zag wires at the back of refrigerators ) which reduces the temperature of the refrigerant to liquid phase. The high pressure liquid is then passed into the throttling device which is a small diameter spiral valve. When the liquid is passed into this small valve, the temperature reduces( the same way as the perfume that comes out of the small opening of a perfume bottle is found to be cooler). The cold liquid is then passed to the evaporator that is located inside the refrigerator. Through evaporator fans, the cooled air caused by the continuous flow of cooled liquid circulated throughout the refrgerator absorbing heat from the objects placed inside. On evaporation, the liquid undergoes phase change to low pressure vapour and is directed to the compressor. The cycle continues…
