A refrigerator commonly called as fridge is defined as a machine which is used to maintain or keep the food materials at low temperature and prevents their spoilage. The food materials kept at low temperature spoils or degrade gradually and can remain fresh for longer time. The refrigerator generally keeps the perishable items at a lower temperature range.
Working Principle of Refrigerator
It works on the principle of thermal equilibrium i.e. when a cold body comes in contact with a hot body than the heat flows from hot body to cold body until they will not attain the same temperature. In the same way a liquid (called as refrigerant) at low temperature is allow to pass through the fridge compartment. As the refrigerant comes in contact with the air, it takes the heat from it and lowers its temperature. This process keeps continue and the temperature inside the fridge lowers down and keeps the food or perishable items at lower temperature and stops or slows down their spoilage time and can be stored for weeks or months.
Main Components
A refrigerator has the following five main components
Refrigerant: Isobutane, CFCs, ammonia.
Compressor: Compresses the vapor and maintains the flow of refrigerant in the cycle.
Condenser Coil: Cools the high pressure vapor and changes it into high pressure liquid.
Expansion device or throttling device: Expands the high pressure liquid, reduces its temperature and pressure.
Evaporator coil: Takes the heat from the air inside the fridge and makes it cool.
Lets discuss the function of each component in detail
1. Refrigerant
It is also called as coolant and is the working fluid for the refrigerator. It takes the heat from inside of the refrigerator and transports it to the outside. Most commonly used refrigerant in the refrigerator are isobutane (used in modern fridges), CFCs and ammonia (toxic gas and not used in modern fridge)
2. Compressor
It circulates the refrigerant during the working of the fridge. It compresses the refrigerant gas and increases its temperature and pressure. Compressor is the heart of the fridge, without it its working is not possible.
3. Condenser Coil
It is present outside at the back of the refrigerator. It has grill tube and looks like radiator. Its main purpose is to cools the hot and high pressure gases from the compressor. When the hot gases pass through the condenser coil, it gets cool down by the cool air of the room and gets converted into high pressure liquid.
4. Expansion Device or Throttling Device
As its names indicated it expands the high pressure liquid refrigerant and reduces its temperature and pressure. The temperature drops to 20 degree Celsius and pressure to 0.6 bar.
5. Evaporator Coil
Evaporator coil is present inside the fridge. It takes the heat from the air inside the fridge and makes it cool. And this cool air inside the fridge takes the heat from the food materials and lowers their temperature.
1. The high pressure and high temperature (80-90 degree Celsius) refrigerant vapor from the compressor enters into the condenser. In the condenser the vapor gets cooled down and changes into liquid.
How condenser cools the liquid?
Since the condenser coil is exposed to the room temperature and when the hot high pressure vapor inside the condenser coil is comes in contact with room air, It gets cooled and changes into high pressure liquid.
2. Now this high pressure liquid has a temperature of 45 degree Celsius and pressure of 8 bar and passes to the throttling device where it expands and its pressure and temperature drops to .6 bar and 20 degree Celsius and partially gets converted into vapor.
3. The partially converted vapor-liquid refrigerant passed to the evaporator coil and it absorbs the heat from the air inside the refrigerator and completely gets converted into vapor. Here refrigerant cools the inside air of the fridge by absorbing its heat. In the evaporator the temperature of the refrigerant do not changes. The cool air inside the fridge is used to maintain the food items at lower temperature.
4. Form evaporator the low pressure vapor enters into the compressor. The compressor compresses the vapor to high pressure. But as the pressure of the gas increases it also increases its temperature. And this high pressure and high temperature vapor enters into the condenser to repeat the cycle.
The cycle that is used in the working of the refrigerator is called vapor compression cycle.
For better explanation about how refrigerator works watch the video given below:
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.bmp "Basic Introduction About Heat Transfer")
