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The working principle of a refrigerator is basically through evaporation. To clearly understand this, we need to look at the second law of thermodynamics. The law states that if a cold object is placed next to a hot object, the cold object will become warmer and the hot object will become cooler. A refrigerator does not cool items by lowering their original temperatures; instead, an evaporating gas called a refrigerant draws heat away, leaving the surrounding area much colder.

To understand more about how evaporation works. You need to know that anytime a substance evaporates, it takes up heat to do so. That’s why we get cold when we are wet, and even get colder when you stand in front of a fan. Because the breeze from the fan makes the water evaporate and making you colder. That’s why people use to keep things cold by putting them in wet polythene sacks and hanging them from trees.

In this article, I will take a look at the science of a refrigerator. Specifically the different parts of a refrigerator and how they actually work together to preserve our food for extended periods.
But before that, let me put you through the different parts of a refrigerator and how they operate.

The compressor:

the compressor

The refrigeration process begins with the compressor. This compressor consists of a piston driven by a motor to “suck in” and compress the refrigerant in a cylinder. This refrigerant is compressed until it becomes very hot from the increased pressure. This hot gas flows through the coils behind the refrigerator, which allow excess heat to evaporate into the surrounding.

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The Expansion Valve:

A Thermostatic expansion valve
A thermostatic expansion valve

The expansion valve is what reduces the temperature of gas as well as its pressure. It also controls the flow of the refrigerant or coolant into the evaporator. This small device is located at the inner back of the refrigerator and it’s sensitive to temperature change of the coolant.

The Evaporator:

photo credit: quora

This is the visible metallic finned tubes we see anytime we open up a refrigerator. Usually made in gold or silver color. This metal is the actual thing that cools the thing we put inside the refrigerator. The finned tubes absorb heat blown through a coil by a fan. The evaporator absorbs heat from what we kept inside, and as a result of this heat, the liquid refrigerant turns into vapor.

The Condenser:

the condenser of a refrigerator
the condenser is where heat is dumped

This is where the refrigerant releases its heat. The condenser consists of a coiled set of tubes with external fins(usually black in color). It helps in the liquefaction of the gaseous refrigerant by absorbing its heat and subsequently expelling it to the surroundings. This is why the back portion of the refrigerator is always hot.

The Working Principle of a Refrigerator

The working principle of a refrigerator is based on the vapor compression and refrigeration cycle. To simplify this further, the refrigerator is an inverse heat engine which transfers heat from a cold region to a hot region. This of course is against the natural flow of heat from a hot region to a cold region. Thus, it requires power. When you pass a low-temperature liquid close to objects that you want to cool, heat from those objects transfers to the liquid, which evaporates and takes away the heat in the process.

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Now let’s. get to the step by step working principle of the refrigerator. The refrigerant flows from the compress down to the evaporator. But before then let me remind you also that the refrigerant in modern refrigerators does no longer uses chlorofluorocarbon (CFC). This is due some environmental hazards which associate with it like depletion of the ozone layer. Thus, modern refrigerators uses HFC-134a (1,1,1,2-tetrafluoroethane),which is environmental-friendly.

The refrigeration process starts with the compressor. The coolant is compressed until it becomes very hot from the increased pressure. Now the hot gas in the coils of the condenser meets the cooler air temperature of the kitchen, it becomes a liquid. Then this liquid is forced through a device called the expansion valve, which goes into the evaporator coils inside the freezer and the fridge. This is where it experiences a pressure drop and once again becomes a cool gas. It then absorbs heat from the contents of the fridge and the whole cycle repeats again.

The refrigerator cycle
photo credit: butterfly field

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