How refrigerator works?We all know when a mud pot in summer covered by a wet cloth around it, the water in the pot become cool.
The reason is the water in the wet cloth absorbs the heat in the surrounding air and gets evaporated and in the process the pot and the water in it became cool. When few drops of a perfume is sprinkled on our hand we get a pleasant feeling of coolness. The reason is the perfume gets evaporated by taking heat from the hand. These examples show that when a liquid evaporates it causes coolness.

Refrigerator (Fridge) works on the same principle.Usually in refrigerator a liquid called Freon (which can be easily evaporated) is used. This liquid is called refrigerant. Inside the fridge there will be an icebox and cold plate around them wire coils are arranged through which Freon liquid is circulated. This liquid will absorb the heat around that place, evaporates and causes coolness in the fridge. The vapor which absorbed the heat comes out of the fridge. This vapor in turn experience contains pressure in a condenser arranged behind the fridge and converts into liquid once again. While converting into liquid it leaves the heat which is absorbed earlier in outside of the fridge.

This liquid which is cold is sent back to the fridge by the condenser through tubes and coils. As this process occurs for a number of times the contents (food stuffs) inside the fridge not only cool to a temperature of nearly 5?c but also remain fresh for considerable time. 

Why a “fridge” makes a kind of noise now and then?Refrigerator makes certain noise in certain intervals of time. The reason for this noise is due to the condenser (compressor) fixed to the fridge is getting “switched off” and “switched on” often.
The condenser in the fridge is attached to a part called “thermostat”. Which controls the inside temperature of the fridge. Once the inside temperature reaches zero degree centigrade as there is no necessity for cooling further, the thermostat sends a signal to the compressor. This is an arrangement made to save electricity afterwards; the temperature inside the fridge slowly increases from zero degrees. When the temperature reaches certain fixed value, the thermostat again sends a signal, so that the electric circuit will be on again. As the compressor is a mechanical system, whenever it is “on” certain amount of noise is produced.