Huge Radiators: Roundup

[dsumanik]

Sorry bro, you need 90 min on average, or your just testing inital hold capacity and not disapation. You need a much longer warm up sequence...

I think what you have to do when looking at this data is simply eat it with a grain of salt from a consumer perspective, not a scientific one. Logically you can simply think, if I plug this rad/fan combo into any given loop, it affects temperatures as so.

Which is what his data gives us, how this rad/fan combo will affect a loop, not efficiency or exact performance. The consumer can then rationalize the cost vs.benefits.

The data as tested cannot define the actual performance winner of these rads because of the fan sizes (as he stated in the introduction of his post)

Specifically looking at the specs of the fans he selected:

140mm 1500 RPM 82.8 CFM
120mm 1900 RPM 75.0 CFM

At full voltage a 400 RPM defecit on the 140mm Has a 7.8 CFM advantage. I would wager that the higher RPMS give better static pressure on the 120mm.

So, how can we possibly compare these radiator based on RPM's?

Perhaps RPM should be thrown out of radiator testing when trying to discover actual dissipation for different sized rads. If all the rads are 120's, or 140's you can get away with it because the initial airflow is constant...but when you compare different formats the airflow needs to be controlled somehow, otherwise the results will skew. So if we calculate C/W with different sized rads against RPM, the data only gives us a trend as to how the radiator is best suited (hi or low speed fan), which is still very useful, but for actual dissipation the temps need to be plotted VS airflow in my opinion...at least if they are going to be on the same graph.

Maybe a single large fan directing a known quantity of air through a shroud with a fixed size opening (i.e a 100x100 square) would be a better way to test dissipation. The recorded temps would be a result of constant static pressure and airflow for a given surface area, call it potential dissipation/inch or something. You could then multiply by surface area to get a decent estimate. Leave the flowrates uncontrolled so this characteristic of the rad is factored in as well.

Another option... maybe in order to compare a 120mm rad vs 140mm rad you need to consider 120mm and 140mm fans with airflow specs that converge over an RPM range, this wouldn't provide similar static pressure, but at lease would eliminate one more variable.

maybe one day martin can do some 140mm fan testing and we can identify the best fans to mate with a 120 vs 140 rad comparison