How does car air conditioning work?

Car ventilation is responsible for air circulation in the car room.

In the figure below, you can see the simplest car air conditioning system.

In the picture above, by pressing the key number 1, it causes the electric current to pass from the fuse box number 2 to the electric motor number 3.

The electric motor (number 3) rotates the blades number 4 and 5.

The air is blown into the air channel number 6 and 8, then it exits from the air vent number 7 and 9 at high speed.

The components of this system are hidden and you can only see dashboard number 10, Air vent Number 7 and 9, and key number 1 inside the car.

The shown system was the simplest car air conditioning system.

For example In the figure below, 7 Air vents are numbered in a car.

Usually, the more advanced the car's air conditioning system has more Air vents.

In the figure below, Air vent number 1, is for heating the side window on the driver's side and removing vapors from it.

Air vent number 2 is for heating the side window on the passenger's side.

Air vent number 3 and 4 are used for heating the feet of the rear passengers.

Air vent number 5, 6 and 7 also help to ventilate the back space of the car room and make the car room to be heated or cooled well.

Every car has keys or levers to adjust the air direction.

In the figure below, you can see a rotary switch that allows passengers to adjust the direction of hot or cold wind.

Other buttons are also used to adjust the car's ventilation, which you can see in the figure below.

In the figure above, the rotary button adjusts the temperature of the air blown from the Air vents.

The middle push button (called push dual) needs a detailed explanation and we have to deal with it in a separate article.

The button marked with a pink line is used for air circulation inside the car (air does not enter from outside the car)

The button marked with a purple line is selected for air intake from outside the car

The application of the button marked with a green line: by pressing this button, the car compressor is activated, when the weather is very hot or you want to reduce the humidity inside the car (for example, in winter when the air humidity is high) you use this key. (we should explain more in another article)

Now we want to see how the car air conditioning system heats or cools the air?

Let us explain step by step.

Look at the figure below. This is a hollow square body with small fins and two pipes A and B are connected to the bottom and top of it. If hot water enters from pipe A and exits from pipe B, the whole set together with the fins gets hot.

If we pass air through the fins as shown in the figure below, the passing air will be heated, as you can see, hot water enters from pipe A and exits from pipe B. The cold air of the car (D) is sucked in by the blower C and blown to the fins (E).The air is heated due to passing through the radiator fins and goes to the car's Air vents (F).

We have understood that the air of the ventilation system is heated or cooled by passing through the blades (fins) of a radiator, now we want to explain the method of this work in more detail.

Cooling

Look at the figure below. The environment inside the car is marked with "A" and the air outside the car is marked with pink color. When the "P" button is active, lever number 1 is positioned to the right and does not allow outside air to enter the ventilation system. Blower "B" sucks the air inside the room through channel "C". The air is blown into the channel "D" and after passing through the radiator "E" it enters the room "A". Since the "A/C" button is on (the A/C button is represented by the letter Q), the radiator "E" is completely frozen by the car's cooling system and The air passing through it is cooled (pay attention to the color of the arrows).

But how is the radiator "E" cooled by the car?

Why does the radiator "E" cool down when we turn on the A/C button?

The radiator that we marked with a letter "E" in this article is called an evaporator.

Now we want to know how the evaporator cools?

To cool the evaporator, methods are used, the full description of which requires the description of thermodynamic laws and topics, and it is not necessary to learn all these laws, here the operation of this system will explain in simple language.

You must have used body deodorizing sprays and you may have amazed why the gas coming out of the spray is always cool.

Don't be surprised, the gas inside the spray is already compressed and you are now decompressing the gas inside the spray.

In general, if we pressurize a gas (compress it), that gas heats up, and if we reduce the gas pressure, the gas cools.

The same method is used to cool the evaporator, we must reduce the gas pressure inside the operator to cool it down and continue this process constantly so that the evaporator stays cool and makes the hot air inside the car cooler and cooler.

So our main goal is to reduce the gas pressure inside the evaporator.

Don't worry, it's very easy.

We use a compressor for this purpose. A compressor is a device that receives mechanical energy and changes gas pressure. The compressor has an outlet and an inlet. The compressor reduces the gas pressure at its inlet and increases the gas pressure at its outlet.

Look at the image below, Compressor 1 receives the mechanical energy from Belt No. 2 (Belt No. 2 is connected to the car engine and receives energy from the car's crankshaft through several intermediaries). Gas is sucked from pipe number 3 (input) and sent to pipe number 4 (output).

As a result of sending gas to pipe number 4, the pressure of pipe 4 is very high and this pipe is heated up. Then, at point number 5, there is a pressure relief valve that allows a small amount of gas to pass through.

After passing through the valve 5, the gas pressure drops sharply and this "pressure drop" causes the "temperature drop" so the gas becomes cold.

The cold gas circulates inside the evaporator number 7 and freezes the evaporator, and then returns to the compressor in the pipe to be pumped again.

Other equipment should be added to optimize the car cooler system.

in the picture below, more complete equipment is shown. We want to introduce you to more components and their functions by re-explaining the steps. Gas is pumped by compressor 3. gas is heated and it is better to cool it to optimize the system. To achieve this goal, radiator 4 has been installed. Hot gas has more time to cool down by passing through radiator 4. A mechanism as a filter to absorb pollution as well as absorb moisture is also placed at this stage, marked with number 5. Car room fan (number 2), evaporator (number 1) and pressure relief valve number 6 have already been introduced.

You may want to know the location of these components in the car. In the figure below, the position of these components are displayed. The car compressor (number 1) is placed next to the car engine. The compressor pulley (number 2) is rotated by a belt (which is connected to the car's crankshaft pulley).The cooler radiator was shown in the figure above with number 4 and its function was explained. In the figure below, the cooler radiator is shown with number 3. The radiator cooler is called condenser and it is placed in front of the car to cool it well. The dryer shown in the figure above with number 5 is shown in the figure below with number 4 and is usually placed in front of the car. The evaporator (No. 6) and the pressure relief valve (No. 5) are placed together and in the inside of car room.

Do you want to know more components of the car cooler system?

Stay with us.

If you are tired, drink coffee, rest, and then continue reading the article.

In the image below, we have shown more components. The route of cooling cycle is shown with number 1 to 13 and many components are known to you. There is no need to introduce components such as condenser fan number 4 because you can guess with your intelligence that this fan helps to reduce the temperature of the gas leaving the compressor. But the pressure relief valve number 8 needs an explanation. Due to the application of the pressure relief valve, this valve should only be located in the path of pipe 7 to 9. So what is the route of pipe 12 to 13? Why is this valve placed in the path of pipe 12 to 13?

The pressure relief valve only reduces the gas pressure in the path 7 to 9 and does not create any obstacles in the path 12 to 13. Question: So why does route 12 to 13 pass through this valve? Answer: To cool valve number 8. You know pipe number 12 comes from the evaporator and still has a little bit of cold. Isn't it better to use this remaining cold to cool Valve 8?

Yes, this is how we optimize the system.

Of course, there are other reasons that we don't want to explain, just know that this process is important for the health of the compressor.

There are certainly other parts and mechanisms.

For example, there are valves in the pipes to control the system pressure and ensure safety issues, or for example, parts for gas cooler charging.

Heating

Internal combustion car engines produce a lot of heat and are usually cooled by water.

In most cars, the heat produced by the car engine is used to heat the car's room in winter.

The heat produced by the car engine is used to heat the "heater radiator".

Look at the image below. By reading the cooling section, you noticed that the "E" radiator freezes only by pressing the "A/C" button, and if the "A/C" button is off, the "E" radiator is neither hot nor cold. But in most cars, the "F" radiator, which is called the "heater radiator" is always hot when the car is on. For heating, the A/C button must be off so that the radiator E does not freeze. Then we need to put the rotary button "S" in the hottest position, with this the lever number 2 goes to the right and the passing air passes over the radiator "F" and is heated.

Now we want to know how the radiator "F" heats up.

Why does the radiator "F" heats up after starting the car?

Look at the image below. The car engine is marked with number 1 and when the car is started, the car engine heats up. The water pump (number 2) is responsible for circulating the "heated water inside the engine" in the path 3-4-5-6 so that the water cools down and returns to the engine. In addition to the mentioned route The water pump makes the water move in the path 2-3-4-7-8-9-10-11-12 so that the heater radiator (marked with number 11) become also heated.

We want to introduce you to the duties of parts 8 and 9. The task of part number 8: This part heats the water passing through route 8 to 12 by electric energy, because after starting the car, it takes some time for the water in the system to heat up. The task of part number 9: when we do not need a heater (summer season), it closes the route 9 to 12 so that hot water does not flow in the car room. Of course, parts 8 and 9 are not available in the heating system of all cars.

The task of part number 4 needs a detailed explanation and should be explained in an article under the title of "the car cooling system".

Dehumidification using air condition system

The air of the environment in which people feel relaxed and comfortable depends on temperature and humidity.

In fact, just as the temperature inside the car is important, the humidity inside the car is also important.

Especially in cold weather when humidity makes the car windows fog up and the driver's vision is limited.

By using the car's air conditioning system, we can control the humidity in addition to the temperature.

We have two ways to prevent the glass from fogging up:

1- Heating the windows:

To heat the car windows, some Air vents are usually used that direct hot air to the windows.

In the picture below, an air vent marked with a green line directs the hot air towards the side window of the car.

To heat the windshield, air vents are using on the top of the car dashboard.

Electric energy is usually used to heat the rear windows.

If you look at the rear window of the car, you will notice that there are conductive lines on it.

When the electric current circulates in these lines, these lines are heated and as a result, the rear window of the car is also heated.

2- Reducing the air humidity inside the car:

We can use the condenser of the car cooler to reduce the air humidity inside the car.

In general, water vapor condenses (turns into a liquid) if it hits a cold object.

Now we have to make the water vapor condense on the car's condenser instead of fogging the car's windows.

Look at the picture below. If you turn on the "A/C" button, the air inside the car first passes through the condenser "E" and this action causes the air to be cooled and moisture-free. Then the air passes through the radiator "F" and is heated. As a result, warm and moisture-free air enters the car room

Question: The air inside the car first passes over the condenser "E", which is cold, and then passes over the radiator "F" which is hot. Is the air cold or hot at the end?

Answer: The power of radiator "F" is more than condenser "E"

For example, suppose the air temperature inside the car is 5 degrees Celsius and we want to increase its temperature to 25 degrees Celsius (which is the right temperature).

5 degrees air first passes over the condenser "E" with a temperature of -20 degrees, and in the ideal case, we assume that the air temperature reaches -20 degrees.

Now, by passing the air over the heater radiator "F" with a temperature of 95 degrees Celsius, the air reaches a suitable temperature (ideally it reaches 95 degrees) and it is enough to heat the air inside the car and bring the temperature to 25 degrees Celsius.

Both the evaporator and the heater radiator are located behind the dashboard of the car and inside the ventilation system.

In the figure below, you can see the opened dashboard of a car, the cooler evaporator is shown in sky blue color and the heater radiator is shown in green color.

Therefore, by using the car's air conditioning system, we can control the temperature and humidity at the same time.

In this article, we tried to describe the operation method and components of the car air conditioning system in the simplest language.

Thank you for taking the time to read this article.