Car air conditioning system PDF
You might have pondered (while stuck on the M60) how the air conditioning actually works, or perhaps you have never given it a moment's thought. Just in case you are curious, let us explain it to you.
Air conditioning like it says 'conditions' the air. It not only cools it down, but also reduces the moisture content, or humidity. All air conditioners work the same way whether they are installed in a building, or in a car. The fridge or freezer is in a way an air conditioner as well. Air conditioning is a field in it's own right, but we'll stick to the main points or a car's air conditioning and the main parts used and a few hints to keep the air-con system running properly.
A number of people don't realise that turning on the air conditioning actually reduces the number of miles per gallon of your car. There is energy used in removing the heat and moisture from the air in the car, and this consumes petrol because of the extra engine load.
Air conditioning's main principles are Evaporation and Condensation, then Compression and Expansion. To the engineer and physicists they talk of thermodynamics - but we'll explain it in our own way here:
Evaporation: You may have noticed that if you rub a little surgical spirits on the back of your hand, then your hand will feel cold. Why is that? It's evaporation. It is because the spirits on the back of your hand start to evaporate. As the spirit evaporates, it takes away heat from the surface of your skin.
Condensation: Have you ever noticed when somebody walks in from the cold into a take-away wearing glasses, their glasses steam up? Why is that? It's condensation. The moist air of the take-away cools as it contacts the cold surface of the glasses and the air has less capacity to hold moisture, so it condenses into water on the glasses.
Heat of Compression: Have you ever noticed when you pump up a bicycle tyre with a hand pump, that the end of the pump gets hot? This is because the energy that you have put into the air by pumping it has not only compressed it, but has also caused the air molecules to push closer together so giving off heat with the friction.
Compression: At some point all gases will eventually become liquid. An example of that would be a can of deodorant - it's liquid inside the can (because you can hear it when you shake it) but is a gas when it comes out and hits your underarm. The pressure inside the can is higher, so the propellant inside is liquid.
Cooling by Expansion: Going back to the deodorant, you will notice also how cold it feels that's because the propellant has just expanded in volume quickly.
Anyway, enough about takeaways, armpits and surgical spirits, but those are the basic ideas that are easy enough to explain. The important question is how does all this fit into making your car's vents blow cold?
Hard tubing and flexible hoses connect all the actual components of the air conditioning in your car. Evaporation and condensation, expansion and compression are the physics of why it works. There are five main components to the whole system, namely the Compressor, Condenser, Receiver-dryer, Expansion valve, and the Evaporator.