Refrigerator is an inseparable part of our modern life. We cannot pass a single day without a refrigerator also known as a freeze. We can preserve perishable goods like fish, meat, uncooked and cooked curry, life-saving drugs for a longer period keeping them at lower temperatures. Bacteria cannot attack food at a lower temperature. They remain fresh for a long time. But how it actually works? In this article, we going to show you how a refrigerator works.
How refrigerator works
Heat is always transferred from an object at a higher temperature to an object at a lower temperature. Heat cannot be transferred from a colder object to a hot object. In a refrigerator heat energy is brought out by a special method. To transfer heat from a colder object to a hot object we will have to expense mechanical energy. This mechanism is called a heat pump. As a result, the temperature inside the refrigerator becomes much lower (lower than 0°C) than the room temperature.
To make a workable refrigerator need something that can absorb heat from the surrounding. The cold liquid is flown through an evaporating coil. This liquid becomes hot absorbing heat from the surrounding. Then the liquid is flown through an expanding valve at high pressure and it is allowed to expand so that it is converted into vapor.
This vapor while passing through the condensing coil gives up heat to the environment and becomes cold. Now, this cold vapor is compressed with high pressure inside a compressor and converted into liquid, and again passed through the evaporating coil.
Mechanical energy is used to run the compressor and to flow the liquid through the evaporating coil. In refrigerators also this mechanism is applied to bring out heat energy by expensing mechanical energy. The construction and principle of action of the refrigerator are given below.
The basic construction of the refrigerator
The main part of a refrigerator is a rectangular cooling chamber that is surrounded by a heat-conducting coil of metal pipe. One end of the coil is connected with the inlet of a compressor kept at the lower part of the refrigerator. Another end of the coil is connected to another coil through an expanding valve.
The second coil is called the condensation coil. This coil is mounted on a fin at the back of the refrigerator. The last end of the coil is connected with the outlet of a compressor. A special type of refrigerant is flown through both coils. The characteristic of the refrigerant is that if it flows through the pipe at high pressure then it absorbs heat from the environment and quickly converted into vapor. The compressor is run by an electric motor. Here is a video to better understand the whole process
Working principle of a refrigerator
When the compressor has started the pressure of the evaporating coil reduced and as a result, the refrigerant is quickly vaporized. For this latent heat is required. The refrigerant is converted into vapor absorbing latent heat from the cooling chamber that is the substances preserved in the cooling chamber.
As a result, low temperature is created inside the cooling chamber. The pump compressed the refrigerant gas at high pressure and flows through the condensation coil. Compressed gas at high pressure flows through this coil kept open outside (this type of coil is seen on the fins at the back of the refrigerator).
This gas releases heat to the atmosphere outside and becomes liquid. This liquid is again flowing through the evaporating coil. As long as the compressor is in action this cycle of condensation and evaporation continues. As a result, the low temperature in the cooling chamber exists.
If the cooling chamber becomes colder more than required then the power supply of the compressor is to be cut off. For this, there is a thermostat inside the refrigerator. When the temperature becomes lower than the requirement the thermostat automatically starts functioning.
- Physics 2nd paper book (Dr. Shahjahan Tapan, Muhammad Aziz Hassan, Dr. Rana Chowdhury)
- Learn Engineering YouTube channel
Here is a PDF download link (Google Drive). This PDF is about the working principle of the refrigerator.
Frequently Asked Questions (FAQ)
1. How refrigerator light bulb works?
Answer: There is a push switch near the refrigerator door. When you close the door, the door pushes the switch with its curve surface. This type of push-switch works completely differently than a normal switch. It disconnects the light bulb when the door pushes it. Now many modern refrigerators use sensors to on and off light bulbs.
2. Which gas used in the refrigerator?
Answer: According to Wikipedia Freon gas is the most common gas used in the refrigerator. Modern refrigerators usually use a refrigerant called HFC-134a (1,1,1,2-Tetrafluoroethane). It does not deplete the ozone layer, instead of Freon.
3. What are the parts and functions of a refrigerator?
Practice Problems
1. Heat transfer from where to where?
Answer: a
2. Which pump used in a refrigerator?
Answer: b
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