How does a cars AC work?

Question

and why does the engine have to e on for it to work?

Answer 1

the engine drives the compressor without the compressor on the refridgerant wont cool yo car

Answer 2

All non jet based AC systems work the same way.

Step one Compress a gas. When you do this all the heat energy that is in the gas gets concentrated in a smaller space. This makes it hot.

Step 2. Take that gas and run it through a heat exchanger to blow off the heat. Heat exchangers work by having metal heat up from the gas then air blows over them to cool the metal. Fins are added to give more surface area. Picture your radiator only instead of water, there is a gas like freon inside.

Step 3. Rapidly expand the gas back to its size. You do it fast so it doesn't absorb heat from the air before you are ready to use it. When this happens the gas has less heat energy because it was blown off in the heat exchanger. So the gas is now cold.

Step 4. Run it through another heat exchanger, only this time the air is cooled as it blows over it and the gas inside is warmed back up. That cold air is ducted into your car.

Step 5 Repeat in a continuous cycle.

The reason your car uses a refrigerant instead of just air is because these gases can be compressed easily into a liquid. This makes the expansion and compression more extreme than just compressing air.

This whole system is run by the engine. Fans and the compressor wouldn't run without the engine driving them by a belt. Some trucks have electric systems that run when the engine isn't. This saves fuel when the driver is sleeping.

Answer 3

The AC compressor works off of a belt driven by the engine, thats why the engine must be running. The compressor compresses the freon causing it to heat up. it goes to a condensor where it is cooled some. Then on to an evaporator where the pressure is reduced rapidly and this causes freon to cool greatly. At the evaporator a fan blows across the the evaporator and this cools the air and the air comes out of the vents in your car. and the cycle starts over

Answer 4

A few scientifc principles get in the way of some of the answers so far.
1) liquids cannot be compressed
2) heat moves from warmer areas to cooler areas
3) the air that passes over the evaporator on the way into the passenger compartment is air that has had the heat removed from it, not air that has had cold added to it.

there are two changes of temperature and two changes of state in a sealed automotive refrigerant system. the belt driven compressor is the pump that moves the refrigerant through the system.

the compressor pulls the hot gases from the evaporator and squeezes them under compression to superheat the gas. That high pressure gas is then pushed to the top of the condensor which is the radiator-like heat exchanger in the front of the car. The gas enters the top of the condensor (hot air rises). As the gas gives off heat it sinks lower in the condensor and exits the condensor as a high pressure liquid. The high pressure cooler liquid moves through a filter then to a metering valve that is regulated by the temperature of the heat exchanger called the evaporator.

the refrigerant is metered into the evaporator by a thermostat device. If too much refrigerant is allowed in, it will freeze up the system. If too little is allowed in, the a/c won't cool. The thermostat allows just the right amount of the low pressure liquid refrigerant to enter the evaporator.

inside the evaporator that low pressure cool liquid absorbs the heat from the air that passes through the coils by conduction. That causes the low pressure liquid to boil inside the evaporator and to expand as it transforms to a hot gas. That hot gas is pulled out of the evaportor by the compressor where it is compressed and sent on to the condensor to start the cycle again.

there are several configurations and styles of the filters, thermostats and metering devices, but the principles remain the same on all automobiles.

Answer 5

Motor turns a belt that turns a wheel on a compressor that compresses the refridgerant gas into a liquid, this liquid goes into an expansion chamber and changes back into a gas and absorbing heat at same time through phase change, this is what causes cooling in vehicle
the same principal works for your refridgerator.

Answer 6

i own a shop and the reason the engine has to be on ,is because when freon is pushed through the condenser coils is gets cold because its being compressed,then it gives off cold which forms on the coil and is then blown off by a fan this is where we get the cool air we feel,that's pretty much it,its really a simple system they way it works,good luck i hope this helps.