Do airplanes have air conditioner units?

Question

how does commercial airplanes generate the air you feel in the cabin? Is that air coming from outside or it it generated by an airplane ac unit? my grandfather had a discussion with someone and he believes the air is generated from the outside air? I believe they must have ac units but I just wanted to get the info from other sources :)

Answer 1

you wont need AC, per say, at a mile hight. it is cold and at a low pressure. pumping air into a compressed cabin and allowing it to escape meets the definition of air conditioning. the change in pressure is enough to suck the remaining heat out of the air. ever felt a compressor and the air storage tank? the compressor is hot and the storage tank (cabin) is cold. of course you wont need that at a mile, it is cold!. they use that on the accent. on the ground an airplane uses traditional AC to keep the cabin cool. so they are both right.

EDIT: Bomba, you are contradicting yourself.  the air at altitude is already dry, cold and at very low pressure. there is barely any moisture to remove. so which is it? is AC used to remove moisture or is that air so dry it damages your sinuses?

i already explained it. in an AC unit the change in pressure is used to convey heat. in a pressurized system, you dont need a second pressurized system to remove the heat. the cabin IS the evaporator coil!

Answer 2

They do have heating and cooling and compressor units run from one of the jet engines. Most of the air is recirculated, with perhaps 5-20% of it fresh air (not sure of this number, it changes from airline to airline and model to model). There has been a lot of discussion on the percentage of fresh air, with flyers wanting more fresh air, as it will reduce the famous colds that a lot of people get from flying, breathing other peoples air. And the airlines wanting more recirculated, as that saves money.

And if you think about it, they have to have heating and cooling and compressor units. In the winter, you have to heat the air. In the summer, you have to cool the air. That's while waiting for takeoff. At altitude, you need to compress the air. Which heats it, and you need that as at 30k feet, the air is very cold and very thin.

.

Answer 3

They do have A/C units which heat and cool when needed as Billruss has said in his first paragaph. Part of the purpose of the cooling is to dehumidify the cabin air to r****d condensation when temperatures get extremely cold at high altitudes. This works much like the defroster in your car which cools to dehumidify and then reheats the inside air.

The low humidity will likewise cause drying of nasal passages and make people suceptable to viruses. I am surprised that professional airline pilots and crew members are not sick a lot.

Outside air is brought in and conditioned to pressurize the cabin and fresh air is also brought in for health considerations like it is in a office building conference room.