1: Evaporator 2: Compressor 3:Condenser 4:Expansion Valve
Room air is drawn by the fan and allowed to pass through cooling coil in evaporator. Suppose room air Temp is at 30°C, after passing the cooling coil it becomes 15°C. Before entering back this air to room, it comes to contact with Refrigerant(say at 10°C), generally used R-22 or R-134A. The refrigerant is allowed to evaporates here by taking Latent heat from room air. Then this vaporized refrigerant passes to condenser through compressor. In compressor where it is compressed.
Now I am going to discuss the function of compressor. We know that Heat is always transferred from high temp region to low temp region. However what happens in Summer time, the atmospheric temp is very high, say above 35°C(generally). But the vaporized refrigerant temp is 10°C, so it is impossible to transfer the heat of vaporized refrigerant to atmosphere. By the convention of eqn: PV=nRT, we know that in constant volume, if we increase the pressure, then the temp also increases. So that after compressed it the temp of vaporized refrigerant becomes too high like 50°C. When it is entered to condenser and comes to contact with atmospheric air and leaves the latent heat for condensation. And then the high pressure liquid refrigerant passes through capillary tube (expansion valve) before entering the evaporator.
A compressor compresses a gas called Refrigerant. It has special properties that is why it is chosen.
The compression makes the gas into liquid form. The compression results in the gas/liquid getting heated. The hot liquid is made to flow in set of tubes and a fan cools the liquid. Then the liquid is released through a small nozzle where it expands and the expansion requires energy which is drawn from the room in the form of heat. The liquid upon becoming gas goes back to the compressor and the cycle repeats.
One question. Why should there be heating and cooling on compression and expansion.
For example, take a 50 kilo heavy rock and drop it from a height. What happens? A big sound occurs and energy is released which sometimes destroys other rocks and things on the ground. No? Similarly when a gas is compressed, molecules of the gas come together, like the heavy rock and earth are coming together. Then energy is released which is in the form of heat. When gas expands the gas molecules move away from each other which requires energy, which is drawn from the room in the form of heat. Suppose you have to lift a 50 kilo rock to the top of a building to be able to drop. You would need energy to separate the rock from the surface of the earth. Similarly with gas molecules going away from each other.
Hope this helps.
The basic principle is that you need a fluid that boils well at ambient temperature. Water isn't good because it boils at 100C even though it absorbs a lot of heat.
So fluids are chosen that hold a lot of heat , boil at a low temperature, and can be compressed from a gas back to a liquid so it can be used again.
Ammonia is a good refrigerant fluid, because it absorbs a lot of heat as a liquid and it boils at about -33C.
So the cycle starts out with a canister of pressurized ammonia ( in this example). The pressure keeps the ammonia a liquid. When you take the pressure off the liquid and let it expand, it turns into a gas but that gas drops down to it's boiling temperature of around -33C. This is called the evaporator heat exchanger and this is the side that faces your room and this cold expanded gas absorbs heat from the room air in going from the pressurized ambient liquid out to the cold low pressure gas.
When this gas has reached the end of the heat exchanger it has warmed up some from absorbing heat from the room. This warmed up gas is then run thru a compressor which pressurizes it back to a liquid. The compressor heats the gas up by doing work on it, so now the heated pressurized gas has to be run thru another heat exchanger called a condenser.
This is the side that vents to the outside. This compressed gas might be about 50C or hotter at first, but as it runs thru the condenser it cools down to ambient temperature of around 20C or so to which the compressed gas turns back to ammonia liquid and is ready to start all over again by being re expanded and absorbing heat again.
Dear Sir/Madam/Friend
please find the attached link. such that you may get clear exposure on working of a Air Conditioner
Thank You
Vamsi Krishna
