No matter if it's the air conditioner on your car, a window unit in a house, your refrigerator, or a 100 ton unit on top of a building , all air conditioners operate on the same principle: Heat transfer or heat exchange, whichever you prefer to say is fine. The idea is to remove (or absorb" the heat from one area and transfer it to another. In this post I'm going to attempt to explain how the a/c system works to prepare you for the auto air conditioner repair post later.
There are three basic components on most modern air conditioners in use today :
There are three basic components on most modern air conditioners in use today :
- The Condenser
- The Compressor
- The Evaporator
Okay, now that we know the parts lets take a look at how the system works.
Low pressure gas freon enters the compressor on the suction side and is compressed into a high pressure gas.
From here it is pumped through the condenser where cool air is forced across the condenser coils removing heat from the freon.
As the heat is removed from the high pressure gas freon it turns into a liquid state.
The liquid freon is then released into a low pressure environment via the evaporator.
As warm air inside the car passes over the evaporator coil the heat in the air is absorbed by the liquid freon.
When the liquid freon has absorbed enough heat to turn it back into a gas it is said to be saturated.
At this point the gaseous freon is drawn back into the compressor and the process repeats continuously.
As you can see this is a simple process of using freon as a medium for transferring heat from the inside of the car to the outside.
Now lets try for a simplified explanation:
Take for instance you have a very hot pan on the stove with nothing in it , if you put a small amount of water in the pan the water will remove as much heat as it can contain to "become saturated" turn to steam. If you had placed a glass lid over this pot as soon as you put the water in it you would see the steam collect in the lid , as the steam cooled "or passed its heat back to the air or lid " it would form into a liquid and fall back into the pot . If the pot was still hot enough it would again turn to steam and collect back on the lid. It would continue this process until the heat was transferred from the pot to the surrounding air down to 212 degrees F which is the saturation point for water at sea level. You can raise the saturation point of a liquid by increasing the pressure.
R 134 freon exist in a liquid state at approximately - 15 degrees F at atmospheric pressure. For it to be in a liquid state at around 80 degrees F it has to be compressed to roughly 85 psi.
Therefore if it is released into a 0 pressure environment it will absorb as much heat as it can contain until it either becomes saturated or the temperature surrounding it is lowered to -15 degrees F. Now in reality the evaporator is not at 0 psi. The compressor will usually pull the suction side down to about 30 to 45 psi on a 90 degree F or so day.This will give R 134 a saturation temperature of around 35 to 50 degrees F. So now you can see how we can remove some heat from air inside the car that is 90 or a 100 degrees.
Now to be able to transfer that heat to the outside we have to raise the pressure on the freon higher than the saturation point for the temperature of the outside air. At 250 psi the saturation point is 146 degrees F, so if it only 100 or 110 outside we can remove some of the heat from the 146 degree freon.
There are a number of devices used to control the pressure differential between the condenser and the evaporator, most cars use either an orifice tube or a thermal expansion valve , while most house units and refrigerators use a capillary tube system.
Well I got a little complicated in the explanation, but hopefully this will prepare you when we get to the air conditioning repair section.
Low pressure gas freon enters the compressor on the suction side and is compressed into a high pressure gas.
From here it is pumped through the condenser where cool air is forced across the condenser coils removing heat from the freon.
As the heat is removed from the high pressure gas freon it turns into a liquid state.
The liquid freon is then released into a low pressure environment via the evaporator.
As warm air inside the car passes over the evaporator coil the heat in the air is absorbed by the liquid freon.
When the liquid freon has absorbed enough heat to turn it back into a gas it is said to be saturated.
At this point the gaseous freon is drawn back into the compressor and the process repeats continuously.
As you can see this is a simple process of using freon as a medium for transferring heat from the inside of the car to the outside.
Now lets try for a simplified explanation:
Take for instance you have a very hot pan on the stove with nothing in it , if you put a small amount of water in the pan the water will remove as much heat as it can contain to "become saturated" turn to steam. If you had placed a glass lid over this pot as soon as you put the water in it you would see the steam collect in the lid , as the steam cooled "or passed its heat back to the air or lid " it would form into a liquid and fall back into the pot . If the pot was still hot enough it would again turn to steam and collect back on the lid. It would continue this process until the heat was transferred from the pot to the surrounding air down to 212 degrees F which is the saturation point for water at sea level. You can raise the saturation point of a liquid by increasing the pressure.
R 134 freon exist in a liquid state at approximately - 15 degrees F at atmospheric pressure. For it to be in a liquid state at around 80 degrees F it has to be compressed to roughly 85 psi.
Therefore if it is released into a 0 pressure environment it will absorb as much heat as it can contain until it either becomes saturated or the temperature surrounding it is lowered to -15 degrees F. Now in reality the evaporator is not at 0 psi. The compressor will usually pull the suction side down to about 30 to 45 psi on a 90 degree F or so day.This will give R 134 a saturation temperature of around 35 to 50 degrees F. So now you can see how we can remove some heat from air inside the car that is 90 or a 100 degrees.
Now to be able to transfer that heat to the outside we have to raise the pressure on the freon higher than the saturation point for the temperature of the outside air. At 250 psi the saturation point is 146 degrees F, so if it only 100 or 110 outside we can remove some of the heat from the 146 degree freon.
There are a number of devices used to control the pressure differential between the condenser and the evaporator, most cars use either an orifice tube or a thermal expansion valve , while most house units and refrigerators use a capillary tube system.
Well I got a little complicated in the explanation, but hopefully this will prepare you when we get to the air conditioning repair section.
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