How cars AC works?

You must have traveled in a car or you? You have enjoyed the AC in car as well. But have you ever thought How cars AC works? What are processes involved in the working of a car AC?
Don’t worry! That’s why we are here. Today in this article, we are going to tell you How cars AC works? So, don’t go anywhere. Stay tuned till end and get the valuable mechanical engineering knowledge with us.

Introduction : How cars AC works?

In the fast growing and technological world, we don’t have that much time to understand the things in detail. We have seen beautiful AC present in our car. But being a mechanical engineer, we have never run our mind in search for How cars AC works?

Actually there’s nothing much difference between the normal air conditioning system and a car air conditioning system. Fundamentals and basics are same. The one and only difference is the structure and design because of lack of space and compactness.

So, let’s see in details about the refrigerant used in car AC, components of Car AC, working process of car AC and many more.

AC system refrigerants

How cars AC works? To understand the Working of car AC we have to know about the refrigerant used in AC.

In the past, automotive air conditioning systems used the R-12 as a refrigerant. R-12 (also known as Freon) is a highly efficient CFC (chlorofluorocarbon) refrigerant that does not burn and is non-toxic to humans. In the late 1980’s, scientists discovered that wide range use of the R-12 was damaging the earth’s ozone layer.
Manufacturers switched to R-134a in the mid-1990’s. R-134a is an HFC (hydrofluorocarbon) based refrigerant that doesn’t have the property of ozone depletion or distortion like R-12. The newest refrigerant is the R-1234yf, which produces a few greenhouse gases. All countries need to use these kind of refrigerants in order to protect the lifeline of earth i.e. ozone layer.

Components of Car Air Conditioning System

  1. Compressor

It is Also known as the heart of an AC system. The compressor provides an increase in pressure to the refrigerant to convert the low pressure vapour refrigerant into a high pressure vapour that also enables continuous flow of the refrigerant through a condenser.

  1. Condenser

The device looks like a small radiator and is used after the compressor as it provides condensing work i.e. lowers the temperature and pressure of superheated vapour coming out of the compressor. Then convert it into saturated liquid form.

  1. Expansion valve

It is a device used in the automotive refrigeration system to amplify high pressure, a low-temperature liquid refrigerator sent by the condenser to release the refrigerant pressure before sending it to the evaporator for further processing. Expansion valve convert the saturated liquid into the form of wet vapour.

  1. Evaporator

It is a device which looks like any other heat exchanger and placed just behind the AC space on the car dashboard of the car. The evaporator absorbs heat from the passenger compartment and converts the wet vapour refrigerant sent by the expansion valve into dry saturated vapour refrigerant. Which in turn also provide fan cooling inside the passenger compartment.

Note – The expansion valve is used in vehicles that enable the passenger to adjust the temperature according to the requirement. Simply by adjusting the knot provided on the dashboard in the passenger compartment.

  1. Receiver-Dryer

It is a safety device used in the air conditioning system of a car or vehicle as there is a possibility that instead of vapour some liquid particles flows into the compressor which could damage the compressor. So the receiver dryer is used between the condenser and evaporator.

Working process of a car AC

In the view of How cars AC works? We have to learn and understand this topic quite carefully. The processes are following:

  1. An evaporator which is another heat exchanger used in AC absorbs heat from a passenger cabinet which in turn converts liquid into an evaporator into vapors that provide cooling with the help of a fan.
  2. This low-temperature vapour is then transferred to a compressor which then raises the pressure above the vapour and converts the dry saturated vapor refrigerant into a superheated vapour refrigerant.

Now the refrigerant is in a state of high pressure and high temperature of vapour.

  1. This high-temperature vapour refrigerant is then sent to a condenser that lowers the temperature of this refrigerant through a forced supply provided by a radiator or separately used air-conditioning.

Now the refrigerant has a low temperature but the pressure of the liquid is almost the same.

  1. This high pressure and low temperature refrigerant are then sent to the expansion valve which also releases the pressure of the refrigerant and converts it to its original state i.e. Wet vapour.
  2. This refrigerant is also sent to the evaporator to continue the cycle.

Note – Between the evaporator and the compressor is used a receiver dryer that converts the remaining liquid refrigerant from the evaporator into vapour before sending it to the compressor.

The receiver dryer also provides system filtration by absorbing foreign contaminants from within the AC system.

General AC System Failure

How cars AC works? To understand this clearly, we also need to understand the AC system failure.

Because automotive air-conditioning systems operate under pressure, they need to be completely closed from the contact the environment. Anything that allows the refrigerant to escape or dirt to get inside can cause failure.

If a leak is present in any part, simply charging the system with a new refrigerant will be a temporary repair. You have to Identify a leak, replace the faulty part, and uninstall and reboot the system.

A system leak will not only prevent the AC system from cooling, but it can also damage the compressor. The compressor can overheat and damage itself by trying to use a very small refrigerant in the system. Compressors usually do not repairable and are expensive to replace.

For proper operation, an AC condenser requires a steady flow of air between its fins. Road debris and pollution can reduce air flow, causing systemic malfunctions. The condenser is mounted directly behind the car grill, leaving it slightly exposed and in danger of being partially closed.

Conclusion : How cars AC works?

So, now its time to wrap up this article on How cars AC works? If this was helpful for you then kindly do share this with your mates and friends.
If you have any queries or suggestions then comment us or simply contact us through email.


Which of the following refers to the term C.O.P. of refrigeration?

Coefficient of performance

The boiling point of ammonia is


For obtaining high COP, the pressure range of compressor should be


The freezing point of sulphur dioxide is


In a refrigeration system, the expansion device is connected between the

Receiver and evaporator

The vapour compression refrigerator employs the following cycle

Reversed Carnot

Rating of a domestic refrigerator is of the order of

0.1 ton

The bank of tubes at the back of domestic refrigerator is

Condenser tubes

The condition of refrigerant after passing through the condenser in a vapour compression system is

Saturated liquid

Freon group of refrigerants are

Nontoxic and non-inflammable

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