0
$\begingroup$

I've been trying to understand how an air conditioner works. And so far I've been able to understand that the basic working is

a cool gaseous refrigerant, is passed through a compressor. where it turns into a liquid. and that in turn goes through some coils, where it releases heat to the outside. Then it goes through some sort of regulator valve, that releases the liquid into a pipe where the pressure is lower, and so it goes back to the gaseous state, and it is cool now, so it can pass through coils. The ac then runs the hot air in the room through these coils, the gaseous refrigerent absorbs this heat and cool air goes into the room and the refrigerent goes back to the compressor and the process continues.

I have three basic questions, why would the refrigerent go back to liquid form when the pressure is increased in the condenser?

Why would this liquid then go on to release heat to the outside?

And how does the refrigerent turn back to a really cool gas?

$\endgroup$
  • $\begingroup$ Things release heat when they are hotter than their surroundings (including just slightly hotter). It really is as simple as that. In this example compression tends to raise the temperature. $\endgroup$ – Andrew Steane Jul 21 at 19:04
5
$\begingroup$

First: how does a fridge work: Fridge

now its a tad blurry but this answers a lot of your question straght away

1) " why would the refrigerent go back to liquid form when the pressure is increased in the condenser?"

Boyles law states that with a constant temperature, pressure is inversely proportional to volume, so if you increase the pressure the volume decreases, which increases density (as mass doesn't change), condensing it into liquid

2) "Why would this liquid then go on to release heat to the outside?"

Because of the gas laws, if you compress something it heats up, from there you have a conductive metal which takes in a lot of the heat, you then have fans, which effectively increase the volume of air for which the metal is in contact with, increasing the rate at which it can lose heat to the surrounding air

3) "And how does the refrigerent turn back to a really cool gas?"

More gas laws! if you have a high pressure liquid / gas, then suddenly drop the pressure of it, it will cool down, which is also why a deoderant can goes really cold as you use up the last of it, you have decreased the pressure, so the temperature drops

$\endgroup$
  • $\begingroup$ The diagram gives good clues. Heat transfer must take place to condense the high pressure vapor, and heat transfer must take place to boil the low temperature liquid. Boyle's law, by itself, is insufficient to explain the refrigeration cycle. $\endgroup$ – David White Apr 2 '17 at 1:24
0
$\begingroup$

The refrigerant contains the same amount of heat whether compressed or not. When compressed, that heat is contained in a smaller volume, so the temperature is much higher. When the temperature of the refrigerant is higher than the hot outdoor air, it will release heat to the outdoors (function of the condenser coils). When it goes through an expansion valve and the pressure drops, the heat in the refrigerant is spread out in a larger volume, so the temperature drops to below your cool indoor temperature, allowing it to absorb heat from inside your house (function of the evaporator coils).

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.