It was initially my goal to estimate CPU wattage by using the following formula:
(Flow Rate*delta T (waterblock outlet - water inlet) *4186)/60
With flow rate in lpm and water temperatures in C
Presumably this should result in a constant value for W over flow rate tests as CPU MHz and Voltage are unchanged. What you actually get though looks like this:
Good agreement from block to block for the temperature rise across the wb; this is encouraging. Some difference doesn't surprise me much because the 3 barb blocks are harder to insulate than the 2 barb blocks. Look what happens when you use the above equation to calculate W:
Les and I have talked about this a bit in the past and are operating under the theory that as flow rate increases, C/W goes down, and wb efficiency (the percentage of the CPUs heat that goes through primary cooling path) goes up.
Anyway the big shift in W estimated by the equation is the reason that I haven't been using C/W for wb tests. Any advice on how to test/think about/explain these results would be most appreciated.
And for the calculation-minded,
here is a spreadsheet
Caveat: The DeltaT (CPU-wb in) from these tests were adjusted down to the average value at 1.50GPM for the review I just published.