How does single Phase Change Cooling work?

G1K777 · May 14, 2019

Hello,

I want to learn how phase change vapor coolers work but I can't find any info about it.

All I know is that the liquid vaporizes (turns into gas) inside the vapor chamber that sits on the CPU, then the gas goes thru the tube into a condenser that turns the gas into a liquid and the whole process starts again.

But I don't know exactly how it works, will a bigger condenser make the CPU run cooler or a bigger compressor. Is this a compressor or a pump? If it works with a liquid... why is it using a compressor and not a pump etc.

Electronics Wizardy · May 14, 2019

look up how air conditioners work, there very similar in operation.

GoldenLag · May 14, 2019

48 minutes ago, G1K777 said:

But I don't know exactly how it works, will a bigger condenser make the CPU run cooler or a bigger compressor. Is this a compressor or a pump? If it works with a liquid... why is it using a compressor and not a pump etc.

it operates on the same principle as airconditioning.

instead of regular heat transfer. the evaporation of the liquid causes it to steal heat from the surrounding air (in this case the coldplate). this is then put into a compressor which puts the now evaporated liquid into a radiator where the liquid can then condense.

a pressure valve then lets the liquid into the coldplate section where it evaporates again.

essentially you have a high pressure zone for condesation where the evaporated liquid is compressed to condensate in a radiator to remove hear. which is then let into a low pressure section with a valve.

think of when you use a can of compressed air and the tip of it gets cold when you use it. if you havent learned why this happens. dont worry, physics class has got you covered.

Spoiler

cold end would be the CPU part btw.

unsungheroist · May 14, 2019

Massai · May 14, 2019

Generally, phase change cooling uses the heat of evaporation.

F.e. - when you want to heat up water, you need just above 4 jouls to raise temperature for 1 Kelvin degree (Celcius) of 1 gram of water.

To evaporate this 1 gram, you need over 2200 jouls.

To get this 1 gram of water to boiling temp, lets say from 20 C to 100C - you need 80 times 4.192 - around 260 jouls.

Evaporation of this gram needs almost 10 times more energy.

Evaporation is a complicated process, but shortly speaking - it can "suck" energy from the material.

Evaporating water can lower temperature of the surface from which it evaporates even BELOW ambient.

Thats how our sweating works - microdrops of sweat evaporate.

Condesation is the oposite process and this heat is released to the material on which steam condensate.

But do not confuse this phase change systems with systems that use compressors.

Compressing gas (air, steam or another gas) heats up this gas. Laws of physics. When you release the gas and pressure drops - the temperature also drops to the level before compressing.

This is used to create a temperature delta, difference between gas and surrounding - you can cool this compressed and warm gas, and then release it - its temperature will drop for the same amount of degrees.

F.e. you compress gas and heat it from 20C to 80C degrees. Your ambient temp is 20C - you run this warm gas through radiator, it cools down to lets say 30C. Than you release, and it cools down for 60C (as it went up from 20 to 80), but starting from 30C, and you have -30C gas.

Sorry, I don't use Freedomheit degrees ;-).

Generally, you don't have to use compressor in phase change system - pump is enough just to push gas to condenser.