How Does a Refrigerator Work?

Talking of modern-day inventions, one cannot undermine the importance of the refrigerator, especially in a tropical country like India where preserving food and eatables from brooding bacteria is a challenge. Besides keeping food fresh and cool, it helps us to store a lot more foodstuff that makes meal planning easy and hassle-free especially in a busy and hectic life schedule.

A refrigerator essentially works on the principle of transmitting heat from one region to the other by circulating a refrigerant that changes from a liquid into a gas. This results in the evaporation of the liquid into a gas, cooling the surrounding area and producing the desired effect. However, no matter how easy it may sound, there is a whole lot of science happening in your large metal box that keeps your food and drinks fresh.

Let’s discover the working of a refrigerator in detail and what causes the large appliance to hum occasionally…

Table of Contents

Components of a Refrigerator

A refrigerator is designed with some basic components that help and facilitate the entire cooling process. Here we familiarize you with some of the basic components of a refrigerator and how they are placed in the entire circuit to stimulate quick cooling and efficient working of your appliance.


A compressor is central to the entire refrigeration process and can be rightly called the ‘heart’ of the refrigerator. It is like a motor that works mechanically to raise the pressure of a gas by reducing its volume. It is designed to handle both the liquid and gaseous states together, unlike other motors. It consists of a motor that sucks in the refrigerant (the coolant) from the evaporator and compresses it in a cylinder as a hot and high-pressure gas. It works like a pump that moves the refrigerant through the coils of a condenser. Thus it acts both like a motor and a pump. Temperature sensors inside a refrigerator signal the compressor to start when the temperature inside the refrigerator rises above the set point.

Modern-day refrigeration systems use different types of compressors like-reciprocating, rotary and centrifugal compressors.


The condenser in a refrigerator is made up of a coiled set of tubes located on the exterior and usually behind it. It changes the liquid refrigerant into the gaseous state by absorbing its heat and condensing it from vapour to liquid. The coiled structure of the condenser makes dissipation of heat easier.

As the condenser coils are exposed to the external environment, they easily get clogged with dirt, dust, pet hair, and other debris. If they are clogged, they shall not be able to release heat efficiently, putting more pressure and strain on the compressor to take the load and work harder.


The coolant or liquid that keeps the refrigeration cycle going is often called the refrigerant. As a special chemical, it is capable of changing its state from a hot gas to a cool liquid. Earlier, fluorocarbons like CFC’s were popular choices as a refrigerant. However, due to their ill effects on the environment, they are now replaced with more eco-friendly refrigerants like ammonia, R-290, R-600A, or HFC-134a also called tetrafluoroethane, etc.

Evaporator or Chiller

A refrigerator cools because it transfers heat from the inside to the outside surroundings and this is done mainly through the evaporator. The evaporator is made up of finned tubes with high thermal conductivity to facilitate maximum heat transfer. A fan blows to pull the heated air to the outside. In the entire process, the refrigerant (coolant) turns into vapour form and flows towards the compressor.

Expansion Valve

The flow of the refrigerant is controlled through the expansion valve also called a throttle valve or capillary tube. The idea of placing the expansion valve in the refrigeration cycle is to decrease the pressure of the refrigerant before directing it to the evaporator. Though a small device, it is extremely sensitive to change in the temperature of the refrigerant.


A refrigerator works at a set temperature and to maintain that temperature, a thermostat is built in the refrigeration circuit. The sensor of the thermostat is connected to the evaporator. When the refrigerator reaches a set temperature, the electrical connection to the compressor is automatically disconnected. This stops the cooling system. Again, when the temperature inside the refrigerator rises, the compressor automatically picks up and the refrigeration cycle begins again.

How Does a Refrigerator Work and Keep Your Stuff Cool?

If you are still wondering how a refrigerator maintains a constant cold temperature and works day in and day out with minimum human interference, then we explain to you how the above components work in pure sync to give you a glass of chilled juice on a scorching summer afternoon. 

Here is a step by step process of the refrigeration cycle…

  1. Inside the expansion valve, the refrigerant or coolant is a pressurized liquid. As it passes through the valve, there is a sudden drop in pressure making it expand, cool, and turn partly into a gaseous form.
  2. Inside the expansion valve, the refrigerant or coolant is a pressurized liquid. As it passes through the valve, there is a sudden drop in pressure making it expand, cool, and turn partly into a gaseous form.
  3. Now, the compressor squeezes the refrigerant, raising its temperature and pressure. It now turns into a hot and high-pressure gas. A compressor works similar to a bike pump. While you pump and compress the air using a bike pump, the heat within increases. Once the compressor has done its work, the gas inside is at high pressure and hot. It now needs to be cooled in the condenser.
  4. The refrigerant or coolant now flows through the thin pipes of the condenser on the back of the fridge, dissipating heat and cooling back into a liquid.
  5. The refrigerant again flows back through the insulated cabin to the expansion valve and the refrigeration cycle repeats itself.

Therefore, heat is constantly picked up or absorbed from the inside of a refrigerator and put outside it, and this cycle continues to maintain a set temperature within the refrigerator.

Why does it feel hot behind a refrigerator?

A refrigerator works on the principle of moving heat from one place to the other. It pumps heat energy from the inside to the outside. Thus it makes the interior of the fridge cold by throwing out heat on the exterior especially at the back through the condenser coil grids.

Why does your fridge keep turning on and off?

All cooling machines work that way. A refrigerator runs on a cycle of on and off as needed to maintain the internal temperature. As the interior cabinet again loses coolness and becomes hot, the compressor turns on and runs for a few minutes. If the fridge (or rather the compressor) ran for 100% all the time, the interior cabinet of the refrigerator would be completely frozen. However, the cooling temperatures are slightly on the higher side to handle the frequent door opening.

Once the set temperature is achieved inside the refrigerator, the compressor switches off and through temperature loss, when the interior again becomes warm, the compressor and the entire refrigeration cycle kicks off. This cycle is an on and off event that normally lasts 5-20 minutes.

That being said, in newer refrigerators, an inverter compressor is used instead of a conventional reciprocatory compressor. And an inverter compressor doesn’t switch itself off, but rather, adjusts its speed depending on various external factors and internal temperature to maintain a steady temperature at all time. Whenever an increase in temperature is detected, either due to room temperature food being kept inside the fridge or opening the door for a long time, the compressor runs at a higher speed and brings down the temperature quickly. Once its cooled down, the compressor runs at a comparatively lower speed which is just sufficient to maintain that temperature.

Final Thoughts

A refrigerator is an incredible machine that has made our lives easier and more convenient. It helps us store food items-both cooked and uncooked as well as a whole lot of beverages to quench our thirst. Though the working of a refrigerator may look complex, fundamentally it is designed on the basic principle of moving heat from one place to the other, by changing the refrigerant from liquid state to the gaseous state.

Essentially the working of a refrigerator is mainly dependent on the compressor-which is the heart of the machine, while all other components play an equally important role in the smooth functioning of the appliance. The usual humming of the fridge that one gets to hear is the compressor kicking on and off frequently and reacting to the thermostat. While the functioning of this home appliance may appear complex, it is brilliantly designed in our modern-day refrigerators to give us a cooling experience without worrying about all the science that goes behind it.


Smart Home Guide Team

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