Originally Posted by defiler2k
The purpose of the reservoir is not to dissipate heat, its to feed the pump and ensure it does not run dry, while the coolant in the reservoir does dissipate heat slightly its not as efficient as when the fluid is going through the radiators that's why you don't see major differences in setups with a big res versus setups with a smaller reservoir.
Agreed. Passive heat loss is nowhere near what you get from a radiator. But my original point was actually about heat capacitance, which is a different thing. It's the reason water is the best coolant (combined with how cheap and plentiful it is)--it absorbs and holds heat incredibly well, which is exactly the quality you want to remove heat from one place (CPU, GPU, etc) and dump it in another (rads). And from basic physics, given the same heat inputs and outputs, a larger volume of coolant will have a lower temperature.
I left out mentioning passive heat dissipation for simplicity's sake, but indeed, all else being equal, a larger volume of coolant in a larger reservoir will dissipate more heat than a smaller volume in a smaller res, meaning once again, the larger volume gives better performance. If you take that to the extreme, with a large enough res (think dozens of gallons if not hundreds
), passive dissipation would do all the work and you wouldn't need even need a radiator.
Admittedly, both of these effects are small considering the two reservoirs Mephobia is choosing between, but it's there.