You are currently viewing Working Principle Of Refrigerator – How Does It Work?

Working Principle Of Refrigerator – How Does It Work?

What does a person look for when he returns home after spending hours in the scorching heat? He first goes and takes out a chilled bottle of water from the refrigerator and drinks it.

Isn’t it wonderful that a machine can keep the temperature inside it very cool even though it’s sweltering outside?

The refrigerator was invented in the 1740s by William Cullen, a Scottish scientist. Though it was nothing like the modern refrigerator we use today, the refrigerator working principle is the same as that of the one we use today.

The Working Principle Of The Refrigerator

image shows refrigerator working principle using thermodynamics

The main principle behind the refrigerator’s working is that a gas or a liquid changes its temperature when forced through a capillary tube or an expansion valve, separately kept in an insulated system where no external heat transfer occurs.

Another principle comes to work in the refrigeration process. When two things in different temperatures come in the vicinity or physical contact, the hotter surface cools down, and the cooler body heats up. This kind of phenomenon is known as the second law of thermodynamics.

As we now know about the different parts of the refrigerator and their working, let’s look at a refrigerator’s detailed working. 

The refrigerator’s primary cooling happens by circulating the refrigerant inside the system by having a looping cycle of shifting the refrigerant’s state from gas to liquid and then again from liquid to gas.

The steps by which this occurs are called evaporation. Evaporation always has a cooling effect on the surroundings. For example, when you sweat and then go sit under a fan, your sweat dries up, and you start feeling cold. This is also due to evaporation.

To start the evaporation and change the refrigerant’s state, there is a need to lower the refrigerant’s pressure. The lowering of pressure is done by passing it through an outlet called a capillary tube. The phenomenon happening here is similar to the one which occurs when you apply an aerosol product like a hair spray.

The aerosol content is the liquid side, the outlet is the capillary tube, and the open space is synonymous with the evaporator. When we release the content in the lower pressure zone of free space, it changes its state from liquid to gas.

watch this video to understand how does a refrigerator work

To keep the refrigerator in running condition, this cycle of state-changing must continue. So the gas again needs to be changed to the liquid state. The transformation can happen by increasing the pressure on the gas and raising the temperature. The working of the compressor comes into action in achieving this state change.

Now after the compressor does its work, the gas in high-pressure condition and is very hot also. It needs to be cooled down, which is again done by the condenser, mounted on the refrigerator’s back.

The condenser’s placement is a very statistical one as the condenser lowers the temperature, its temperature rises. So keeping it open in the back allows the condenser to radiate this heat off to the atmosphere and do its work efficiently. Now, when the gas is cooled again, it again transforms to a liquid state.

After this, the cycle starts yet again, and by it, the refrigerator maintains the desired temperature.

Image Showing R32 refrigerant gas used in Air Conditioner

We saw how the gas inside the refrigerator, which we call the refrigerant, is responsible for cooing the refrigerator. Previously CFC (chlorofluorocarbon) was used as a refrigerant, but this gas is very harmful to the environment and is directly responsible for depleting the ozone layer. Hence, this gas is not used this day, and HFC-134a is used as its substitution in most refrigerators today.

The refrigerator has been a revolutionary invention in the course of mankind. It made a transfer of food from one place in the globe to another place possible, and today the entire food business is heavily dependent on refrigerators. The refrigeration principle is an interesting one, and it shows how one can change the world by simply using some physics laws.

Refrigerator Components And Their Functions

This definition may look much scientific and complex to an ordinary person, and to understand it correctly, one needs to know the detailed working mechanism of a refrigerator. Still, before knowing the working mechanism, it is essential to learn about the different refrigerator parts and their tasks.

Image shows Refrigerator compressor working system


it is the most crucial part of a refrigerator, and the entire cooling mechanism depends on this part. The compressor is a device that spreads the refrigerant throughout the system and makes the refrigerant hot by putting pressure on the internal circuit’s warmer part.

refrigerator condenser, Evaporator, Expansion Valve, Condensor working principle


it is a spiral set of tubes placed along with external fins at the refrigerator’s back. The refrigerant used is present in a gaseous state. The condenser’s work is to liquefy this refrigerant by absorbing the refrigerant’s heat and then emitting it into the surroundings. That is why you will always feel a gush of hot air coming from the refrigerator’s backside, coming from the condenser.


this is the element of the refrigerator that cools down the refrigerator. As the name suggests, the evaporator’s main aim is to turn the liquid refrigerant into a gaseous state through evaporation. While doing so, it cools the surroundings, and the temperature inside the refrigerator drops.

Capillary tube

it is a very thin tube that does the work of an expansion valve. The liquid refrigerant travels through the capillary tube and is distributed into the evaporator, where a low-pressure environment is maintained.


The thermostat’s function is to look after the refrigerator’s temperature and switch on and off the compressor when required.


it is the element under which the cooling happens. It is also known as the coolant and is in a continuous cycle of changing its state from liquid to gas and again from gas to liquid.

Chetan Rana

Chetan is an engineer with a specialization in electronics and communications. During his spare time, he cooks, writes blogs on the latest home appliances, electronics.

Leave a Reply