Quote:
Originally posted by jtroutma
If we have a very high flowrate through the entire system, the CPU will get rid of its heat fast but the radaitor will not have very long to get rid of it (so it goes right back to the CPU and gets warmer IF we have a low flowrate, the radiator has time to remove the heat but the CPU cant get rid of the massive amounts of heat it is making fast enough (hence high temps).
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Ahh - I was just waiting for someone to post this old argument up.
I was going to say flowrate doesn't effect how fast the CPU cools off - but in light of gmats post of "... When flow rate increases, surface area does as well..." I'll instead say that flow-rate has a relatively low impact on cpu temp relative to the temp delta between the coolant and the WB. So your first sentence is invalid = the CPU will get rid of it's heat fast IF the coolant is at a low temp. If that coolant is also moving fast, then it will make the CPU even cooler. However - because it is moving fast, each unit of water (again, molecule, drop, gallon, whatever) that passes through the block will absorb less energy and cooler water will be entering the rad.
If cool water is entering the rad - the rad will be inefficient (see my first post for explanation) The water will be not much cooler by the time it exits the rad again. Though this is not a problem, so long as it is cool coolant returning to the CPU. As the system runs for a while the coolant temp will rise to a balance where the coolant entering the rad is hot enough for the rad to be efficient enough to dissipate as much heat as the CPU is putting off. This is much more dependant on the average temp of the coolant in the rad than the length of time the coolant spends in the rad.
So - the faster the water is moving, the less energy each unit of water will pick up on a lap around the circuit, and the less energy it has to dissipate as it passes through the rad. The rad is a LOT bigger, and has a LOT more surface area than the block, so that unit of coolant should have no problem releasing it's energy into the rad in it's time through there, as compared to the small amount of energy it absorbed in the very short time it was inside the block.