Phase Change Vapor Cooling question

[CreePinG_DeatH]

I can't remember exactly what the deal with phase change coolers was, but someone will help me out :-) . Would there be any advantage to cooling the radiator in a phase change setup with water? Would it take any strain off of the compressor? Any benefits whatsoever? Just a random thought rattling in my head.

[UserName]

in a phase change refrigerator yes. Infact i think the overclocker does that.

in a phase change heat pump (Pipe) less so but yess too!

[CreePinG_DeatH]

Do you happen to know what the benefits were at all? Or just know it helped out some?

[UserName]

phase change requires pumping to recompress the gas. if the gas likes being compressed it's easier. If not it's harder. Compressers are set up for a temp dif between the colsd parts and the hot parts. The colder you keep the cold parts the colder the cold parts will get. the to a point comes in here.

I have heard of peoples putting the house AC compressers in a hole in the ground filled with water and cutting their cooling bills in half.

I don't think thers a rule of thumb, but i think the improvment will be pretty good.

[CreePinG_DeatH]

ohhhh ok.... so it's sorta like the delta temperature with Peltiers then... Excellent...

So now if I get a vapochill, I can use that for the CPU, possibly with a PELTIER, and then watercool my graphics card.
Booooooyaaaaaahhhh

[Tiger]

Most domestic refrigerators will give an interior temperature of about 1C at max setting. If fans are placed in the interior and that air circulated over the evaporator panel then it is possible to improve this situation. It must be born in mind that there are a number of heat transfers going on when this kind of thing is attempted and as you know air is not a good conductor. From work I have done I would say that it is not an efficient method. I tried using a antifreeze solution in the freezer compartment as the heat dissipator (radiator part) and ran the coolant through this bath. It was not a success. The full area of the evaporator is not being utilised. If additional fins could be added to the evaporator, thereby increasing the area of contact with the air it may work. As a standard unit you would probably get some benefit initially but the unit will not be able to keep up with the heat load.

[Koooler King]

A phase change cooler is basically a refrigerant system without the compressor pump. In a traditional A/C refrigerant system, it relies on the pump power to raise the gas pressure and tempurature, the hot gas is then cooled with a radiator (aka condensor) to become a liquid, then is expanded to allow it to cool to colder than it was at first, then a second heat exchanger, called an evaporator, cools the air from the cold fluid that goes through it. In turn, that cold refrigerant is now warmed by the air in the evaporator, it turns back to a gas, and then the compressor raises the gas pressure, and the cycle repeats. Think of a circulating loop with alternating hot and cold spots and alternating liquid and gas zones.

In a passive phase change cooler, the working fluid is chosen so that it will change from liquid to gas and back to liquid at the desired tempurature you wish to cool to, say 50 deg. C for your cpu chip, without the need for a pump, relying just on the liquid evaporation and gas condensation that happens at a particular temperature. Unfortunately, there are few fluids that do so exactly at 50 deg. C at room pressures, and they are mostly expensive or dangerous. To that end, a gas refrigerant such as R134A will work if at high pressure, or plain water will do so if at a partial vaccuum so as to reduce the boiling point to 50 deg. C (remember at normal room pressue, water boils at 100 deg. C).

Well, that is the theory of operation ... what the phase change actually does in practice is raise the thermal conductivity of the heat sink beyond what it might otherwise be if made of solid copper or aluminum. I have tried one of those phase change coolers, it was a TS Heatronics unit ... cost about $100 US ... it was only a fair performer ... thermal resistance about 0.300 Deg. C / W, you are better off using a good copper heat sink such as an Alpha with a decent fan. Good Luck.

Koooler King

[CreePinG_DeatH]

No No No.... What I meant by phase change was Something along the lines of the active coolers like a Vapochill. I know you are talking about heatpipes or heatsinks with the vacuum bases. I was just wondering if I cooled the radiator (condensor) in the vapochill setup as supposed to with a fan, if I would get better cooling results of any kind.