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Originally posted by pHaestus
forced convective heat transfer is related to turbulence and surface area. Turbulence is directly related to water velocity, not flow rate, by the appearance of Reynolds number in calculation.
I think the term I am digging for is called the h coefficient (encompasses the S.A. and Re and some more terms) but I dont have any of that in front of me at the moment. I am betting that Dave or Bill know it much better.
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Heat transfer problems like these will often begin by calculating the convective heat transfer coefficient h on all surfaces where there is significant heat transfer and the conductive heat transfer coefficients k through all solids where there is conductive heat transfer. The areas to which k and h apply must also be known. In cases like these where there can be a long chain of k's and h's - such as the radiator where there is convective transfer from the water to the tubes, conductive transfer across the tubes, conductive transfer along the fins, and convective transfer across the fins and tubes to air - this approach becomes very calculation intensive and error propogation becomes a major problem.
Anyway, if these things are done well, you can find the difference between the temperature of the CPU and the temperature of the air through the radiator by this relationship:
heat = UA (Tcpu - Tair), where
1/(UA) = 1/(kA,block) + 1/(hA,block) +1/(hA,water-radiator) +1/(kA,radiator tubes) +1/(kA, radiator fins) + 1/(hA, radiator fins/tubes-air)
That's the theory, but since most of these coefficients and areas are incredibly hard to determine, a technique called the Wilson method exploits these sorts of relationships to determine the coefficients.
Oh, also:
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You see "head loss" used over "pressure drop" by engineers and mfgrs because the numbers for head loss are not dependent on the identity of the fluid being pumped. For our purposes, pressure drop and head loss are interchangable I think.
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Head loss in a centrifugal pump is highly dependent on what sort of fluid is pumped. Head loss numbers are always for water unless otherwise stated.
Alchemy