There are four important parts of a refrigerator: compressor, condenser, expansion valve and evaporator. Freon gas passes through all these parts continuously in the form of a cycle and undergoes various phase and temperature and pressure transformations. Freon acts as the media for transfer of heat.
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You must be using your refrigerator since a number of years, but do you know how it works? Well, refrigeration is the process of maintaining temperature in a space lower than the surroundings. In this process heat is removed from the source at low temperature and thrown out to the source at higher temperature. Refrigeration is the process of heat transfer against the natural flow of heat which is from high temperature to low temperature. This heat is carried by a fluid, usually the Freon gas.
There are various parts of the refrigerator. Freon gas passes through these parts and undergoes various phase transitions. The flow of this gas through various parts of the refrigeration system is called a refrigeration cycle.
1) Compressor: Compressor is the heart of the refrigeration system. The power required for transmitting heat from low temperature space to high temperature space is given here. When Freon gas passes through a compressor it gets highly compressed i.e. pressurized and its temperature also becomes very high. As it leaves the compressor, Freon gets converted into the gaseous state.
2) Condenser: All the heat the Freon has absorbed from the substance at low temperature is thrown out to the atmosphere via the condenser. For household refrigerators, the condenser is usually a coil of copper exposed to the atmosphere. When Freon passes though this coil it gives up its heat partially to the atmospheric or surrounding air and its temperature reduces, but its pressure remains unchanged. In case of the bigger refrigerators water cooled condensers are used.
3) Expansion valve: When the high pressure and low temperature Freon passes through expansion valve its pressure reduces suddenly and along with it its temperature also reduces suddenly and drastically. In the household refrigerator usually capillary, a thin copper tube is used as the expansion valve. Freon leaving the expansion valve is partially in liquid state and partially in gaseous state.
4) Evaporator: The freezer section of the refrigerator is the evaporator which is in the form of various coils of copper or aluminum tubing. Here the foods or the substances which are initially at higher temperature are kept for cooling. When the low temperature and low pressure Freon passes through the evaporator, it chills the freezer space and food items kept here. It absorbs the heat from the substances to be chilled and so its temperature raises as does its pressure. It leaves the evaporator or freezer in the vapor state and then enters into the compressor where the cycle is repeated.
The refrigeration cycle of the Freon keeps on repeating indefinitely till your refrigerator is running. Since the Freon vapor is compressed in this cycle, it is also called as Vapor Compression Cycle.