Refrigerator Heat Pump

The working of the refrigerator is simple to understand, in this type of system, we have a source through which heat is taken from the surroundings and another system as a sink through which heat gets disposed of. 

A refrigerator we have at our homes works on cooling through the evaporation principle and there are three steps by which a refrigerator or a fridge works:

• Cool refrigerant is passed around food items placed inside the fridge.  

• A refrigerant absorbs heat from these food items.

• A refrigerant transfers the heat to the relatively cool surroundings. 

Refrigerator Thermodynamics

The working principle of a refrigerator is based on the second law of thermodynamics. So, there are the following five steps because of which working conditions are observed:

• First:  the Evaporator coil removes heat from the object.

• Second:  there is an expansion valve that evaporates the gas.

• Third: A cold liquid gas is passed through the compressor.

• Fourth: Hot gas is disposed of in the surroundings.

• Fifth: A metallic coil dissolves heat into the gas.

These five are repeated endlessly and we get chilled food items. 

Components of A Refrigerator 

There are five components in a refrigerator; these are as follows:

• Expansion valve

• Compressor

• Evaporator

• Condenser

• A specialized gas called refrigerant

Refrigerator Working Principle

Do you what is the refrigerator working principle? Well! A refrigerator works on the principle of vapor compression refrigeration cycle in which there are four components viz: expansion valve, compressor, evaporator, condenser, and they all are connected with copper/steel tubes. 

The refrigerator has a low boiling point that is about - 20℃. The freezer is surrounded by the evaporator tube so, when we keep any food item in the refrigerator, the evaporator tube absorbs the heat from this item after this, a liquid refrigerant is converted into vapor.

Now, the vapors are compressed by the compressor to high pressure and temperature. The heat generated is then rejected to the atmosphere from the compressor from vapor to liquid state. Thereafter, this heat again passes through the expansion valve and moves to the evaporator, and so on. This cycle keeps on repeating and cools down the air inside the fridge.

(Image to be added soon)

Working Principle of Refrigerator With Diagram

• Expansive Valve

The expansive valve is also known as the flow control device. An expansion valve controls the flow of the liquid refrigerant or simply the ‘coolant’ into the evaporator. This device is very small in size and also sensitive to temperature changes of the refrigerant.

• Compressor

The compressor comprises a motor that ‘captures in’ the refrigerant from the evaporator and compresses it in a cylinder to generate a hot, high-pressure gas. 

Below is the image for the compressor inside the standard refrigerator:

(Image to be added soon)

• Evaporator

The evaporator is an exact part that cools the foodstuff kept inside a refrigerator. It consists of finned tubes that are made of metals with high thermal conductivity to maximize heat transfer that absorbs heat expelled via a coil by a fan. The evaporator absorbs/seizes heat from the foodstuff kept inside the fridge, and as a result of this heat, the liquid refrigerant vaporizes.

• Condenser

A condenser contains a coiled set of tubes with external fins and is located at the backside of the refrigerator. 

A condenser helps in the liquefication of the gaseous refrigerant by absorbing its heat and instantaneously expelling it to the surroundings.

Now, as the heat of the refrigerant is disposed of, its temperature drops to condensation temperature, and it again changes its state from vapor to liquid.

The below image shows the condenser coils that we can see at the rear of our refrigerators:

                 (Image to be added soon)

Now, we are left with one more component and that is refrigerant or simply a coolant, so let’s understand its working as well:

• Refrigerant 

Refrigerants are basically referred to as the coolant, it is the liquid that keeps the refrigeration cycle continued. 

The liquid which is discussed above is actually a specially designed chemical that is capable of alternating or changing its state between being a hot gas and a cool liquid.

In the 20th century, fluorocarbons, especially CFCs, were a common choice as a refrigerant, since they have caused havoc in our environment, so, now they’re being replaced by eco-friendly refrigerants, such as ammonia, HFC-134a, R-290, R-600A, etc.

Difference Between Heat Pump and Refrigerator

The difference between a heat pump and refrigerator is simple; let’s understand it:

A heat pump working principle is that a device transfers heat energy from a source of heat to the thermal reservoir. Heat pumps move thermal energy in the opposite direction of spontaneous heat transfer, by absorbing heat from a cold space and releasing it to a warmer one; however, a refrigerator is a household appliance that is passed a cooler temperature than the external environment. It makes the objects cooler than the normal temperature.