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What is the Working Principle of a Refrigerator? The Secrets of its High Energy Efficiency

Have you ever wondered what is the working principle of a refrigerator? Today is the day we will unveil the truth behind it. So stay tuned.

Refrigerators are an integral part of every household. The whole mechanism of refrigerators depends on some simple and interesting scientific principles. Now let’s dive into what is the working principle of a refrigerator.

In this article you will get an idea about these aspects:

  1. The basic principle of refrigerators.
  2. Operation of modern refrigerators.
  3. The secrets behind their high energy efficiency.

The Basic Principle of Refrigerators 

It is simple. Mostly, you need to pass a colder liquid. The flow should be continuous around the object you want to be cool.

Let’s learn in-depth about how this continuous cold liquid flow takes place inside a refrigerator.

Throttling Device

It is a simple device. But, its work is the most crucial component of refrigerators. It dissipates pressure energy and converts it to thermal energy. It is a capillary tube. The throttling phenomenon produces a cold liquid. 


The First Phase:

  • For effective throttling, at the inlet, the refrigerant should be at a liquid state under high pressure. 
  • The throttling device is an obstruction to the flow. 
  • A huge pressure drop occurs when the liquid flows through it. 
  • As the pressure drops the boiling point of the liquid comes down.
  • Thus the refrigerant liquid evaporates the energy in need.
  • Such evaporation comes from the refrigerant. So its temperature drops.

If you check the temperature across the throttling device you will notice this drop. Please note that only a portion of the refrigerant evaporates here. This is one important property of the refrigeration fluid. It should be able to change the phase while varying the pressure under normal temperatures.

Second Phase:

The next phase is simple. You just need to pass the cold liquid over the body which you want to cool down. 

  • During the heat absorption process, the refrigerant further evaporates.
  • It transforms into pure vapor.

The Evaporator 

The refrigerant temperature does not increase. Because there is a change of phase here. This heat exchanger is what we know as the Evaporator. One can maintain different temperature levels with the help of clever airflow circulation inside the refrigerator. Here, the evaporator fan comes in handy. 

So we are now successful in producing the required refrigeration effect.


What is the Working Principle of a Refrigerator- compressor

Now, if we need to take this low-pressure refrigerant to a state before throttling. So, we need high-pressure liquid. Then, we will be

able to repeat this process.

So the first step is to raise the pressure. This is where a compressor comes in. This is its

purpose. The compressor will raise the pressure back to its initial value. Here, the compression of gas also increases the temperature. This is unavoidable.


Water drops on fridge
Water Drops on Fridge

The refrigerant is high-pressure vapor. To convert it to a liquid stage, we introduce another heat exchanger. This heat exchanger fits outside of the refrigerator. Thus it will liberate heat to its surroundings. Vapor will convert to liquid. The temperature will reach a normal level. This heat exchanger is what we know as a condenser.

Vapor Compression Cycle 

Here, the refrigerant is back to its initial state. So the throttling device can use it again. Now, just by repeating this cycle over and over, we will be able to achieve a continuous cooling effect. This cycle is more specifically called the vapor compression cycle.

We can evaluate the refrigerator performance using a term coefficient of performance. The coefficient of performance is output divided by input. So we can easily define the coefficient of performance as


  • This is the most basic refrigerator possible ever.
  • This refrigerator will work well in theory however in practice it will face many issues.

Let’s see what these issues are and how to overcome them

The problems:

  1. One major issue is the frost developed in the freezer compartment.
  2. The circulated air has moisture content inside it.
  3. When the air comes in contact with the cold evaporator coil, it will condense and form a frost around the coil.
  4. This ice coating prevents further heat transfer and the refrigerator becomes inefficient over time.

Operation of modern refrigerators

Modern refrigerators can solve the problems of primitive refrigerators. 

What is the Working Principle of a Refrigerator
What is the Working Principle of a Refrigerator

The solution:

  1. One great way to solve this issue is to remove frost occasionally with the help of a heating rod.
  2. You can see a pan and water condensate at the bottom of your refrigerator.
  3. Moreover, in modern refrigerators, you won’t be able to see the condenser fins at the back of the refrigerator.
  4. There they use a compact condenser arrangement.
  5. A cooling fan assists this compact arrangement and here you can achieve the same heat rejection purpose.
  6. The hot air can easily expel the water condensate. The water condensate forms during the frosting.

Modern Refrigerators 

Modern Refrigerators
Modern Refrigerators

The basic mechanism of modern refrigerators:

  • You can see two refrigerant lines outside the refrigerators.
  • One takes the cold liquid from the capillary tube to the evaporator coil. 
  • The other exits the vapor from the evaporator.

However, if you check your home refrigerator you can see only one line on the outside.

Why is this the case? 

The most crucial part of the refrigerator is the capillary tube.

The capillary tube:

  • It is not a spring-like device
  • The capillary tube can be a long straight tube 

As a result, you see only one line on your home refrigerator. This straight capillary tube runs inside the evaporator exit coil. This simple technique has major advantages.

The Secrets of its High Energy Efficiency

The advantages of one line capillary tube:

  • We know that during the heat absorption process at the evaporator the refrigerant temperature does not rise, only its phase changes.
  • When the capillary tube comes in contact with the evaporator exit line, it brings down the capillary tube refrigerant temperature by a great degree.
  • This in effect will lead to greater temperature drops in the capillary tube.
  • It creates a better refrigeration effect
  • On the other hand, the evaporator exit coil absorbs heat.
  • This ensures the refrigerant in the evaporator exit line transforms into pure vapor.
  • This is good for compressors that are designed to handle only pure vapor.
  • A filter dryer removes any moisture contents in the refrigerant which traps the compressor operation

The secrets behind their high energy efficiency

Digital Inverter Compressor 

Let us now explore the most recent innovation in refrigerators. It has transformed modern refrigerators. Digital inverter compressors are the heart of any refrigerator. It is the device that gives life to the whole system.

How the temperature controls it:

  1. You know that the compressors in old refrigerators will either be on or off.
  2. This is a single-speed technology. 
  3. When the inside temperature of the refrigerator reaches an optimum level, the compressor turns off. 
  4. Again, when the temperature goes above a certain limit, the compressor turns on.

So you can see that the temperature control inside the refrigerator is not smooth. Moreover, such abrupt speed variation of the compressors will lead to durability issues. With the help of a digital inverter compressor, a variable compressor speed is possible. As a result, we can achieve a smooth and efficient evaporator temperature control here. 

Here the ac power is converted to dc using a controller. The controller supplies electric power in variable frequency to accurately control the motor speed. The most common motor in use in this technology is a BLDC digital inverter compressor. It consumes at least 40 percent less energy in comparison to single-speed compressors. Hence, you can understand what is the working principle of a refrigerator.


I hope you enjoyed my ultimate guide to what is the working principle of a refrigerator. 

Now I’d like to hear from you: which technique from today’s guide did you know? Are you going to share this with your friends? 

Either way, let me know by leaving a quick comment below.

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Sarhan Bakshi
Sarhan Bakshi
I am simply a writer out in search of something new. In the process, giving you all a taste of the fruits born from my intellect.

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