Originally Posted by Jakusonfire
This is on the right track but a bit confused, and / or confusing. At room temp water has about four times the specific heat capacity of air.
Keep in mind also that specific
heat capacity means it's 4x when comparing equal mass
. Since air is a lot less dense than water, when you compare by volume, the ratio is much, much higher, approximately 3400:1 (see note * below)
. I think that's more significant for PC watercooling purposes since air and liquid flow rates are a big part of things, and in a typical home environment, when we talk about ambient and coolant temps it's a lot easier to measure the quantities of air and water involved by volume than by mass.
"For every 2 degrees the air heats going through a rad the coolant only drops one degree"? That doesn't seem to make sense. If ambient is 20C and it is warmed to 30 by the rad then water would be 25C making the air hotter than the water. This sort of fixed ratio doesn't really exist. Air coming out of a rad will be quite close to water temp depending on speed of air flow and efficiency.
The air will be raised in temp by a certain number of degrees based on water temp but what temp is the water being cooled from? its not really, its just being heated til it expels as much heat as is being put in.
I think I know what you're saying but I can't quite follow this either to be honest. Thermal capacity expresses the amount of energy (heat) needed to raise a given quantity of a substance by a given temperature. So it's important to keep straight the difference between heat and temperature, and you also can't leave out the masses or volumes when talking about it. So the right way to phrase it is:
It takes the same amount of energy to raise the temperature of 1g of water by 1 degree as it takes to raise approx. 4g of air by 1 degree (or 1g of air by 4 degrees)
Cooling 1g of water by 1 degree will raise around 3400ml of air by 1 degree
If you consider that a typical loop might contain around 1 quart of water, by my calculations that means cooling the entire loop by one degree will raise the temperature of about 120 cubic feet of air by one degree.
Of course, since your chips are constantly introducing heat when the system is running, there's a continuous flow of energy without the coolant temp necessarily dropping. But if your coolant is 10 above ambient when you turn the system off, assuming a typical room size around 1000 total cubic feet, cooling the loop back to ambient will raise the entire room temp by around 1.2 degrees.
But since the ambient has gone up, the amount it can cool is a bit less. Heat capacity values also fluctuate with temperature, atmospheric pressure, relative humidity, etc. etc... physics is hard, which is why I'm not a physicist * Nerd note: I'm taking values from the table here, comparing water at 25C with air at "typical room conditions").Edited by threephi - 5/14/14 at 6:45pm