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Originally Posted by jaydee116
I am also thinking you're making it harder than you have to to get the same data. Instead of measuring air temps you can just measure the water inlet and water outlet of the radiator.
Say the water in is 26C and the water out is 25C with a Panalfow 120MM at 5 volts. Then you raise the voltage to 12 and the water in is 25C and water out is 23.5C....
At 7V you get 1C of cooling.
At 12V you get 1.5C of cooling.
If you have a decent flow meter you can add in a GPM to make it a little more usefull.
I can kinda see how that might be usefull or interesting if nothing else.
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The delta across the rad doesn't change with changing airflow in a closed loop, only with changing waterflow. The delta represents the load so with 100 watts at 1gpm the delta will be something like .37C ( I don't remember the actual number) and at .5gpm it will be double at .74C regardless of airflow. The airflow will change the input temp though so you would see something like this
fan@7volts water in 26.37C water out 26C
fant@12volts water in 24.37 water out 24C
assuming 1gpm and 100watt load
Remember that Bill uses an open loop test with a constant input temp so he can use the rad delta to measure performance
Personally, I don't trust Bill's (or Joe C's) method of using rad delta as I feel the measurement is too easily distorted by temp gradients in the waterflow which I think explains pH's fluctuating rad delta as well.
Such a gradient is problably most evident when you look at the results of the bi extreme rad with low airflow. The front row will remove a higher percentage of heat than the rear row creating two distinct water temps with only a split second to converge before reaching the output sensor.
The method used to keep the input water temp constant may cause a temp gradient as well, compounding the problem.
In a close loop test, a temp gradient will be too small to have any effect on the final result. The main problem is you would need to know how the pump heat changes at different flow rates in order to generate a proper c/w measurement.