Pro/Forums - View Single Post - How do you calculate how a rad performs based on the data?

Marci · 11-01-2007, 07:12 AM

Basically same way as Jaydee...

The only way I've ever managed to translate the data into useable is giving folks a "with this fan, this heatload, this flowrate, you can get your coolant to within XX degrees of ambient" based purely on the deltas Bill used in the Thermal Dissipation Charts. Coolant temp is all I'll aim people for... can't predict final CPU Temp / GPU Temp etc due to the differences in everyone's Thermal Resistance testing etc...

The formula in the spreadsheet-source of Bill's PA Series graphs (at www.thermochill.com/PATesting) allows me to extrapolate different air > coolant deltas... standard graphs are at dT of 10... graphs HERE are extrapolated for a dT of 15... could recalc `em for an extrapolated dT of 5 too... but then the airflow required to cool the given heatload tends to be ridiculous when it comes to the noiselevels that airflow would present, hence not bothered with dT5 yet...

S'all very loose and inaccurate but it's as good as I can explain... and folks seem to understand the concept...

I summarised it into a 5-step procedure using combination of ExtremePSUCalc to (over-)estimate heatload, Martin's Flowrate calc to get the flowrate, Heat Dissipation graphs to roughly gauge the CFM required, then Cathar's Fan-on-Radiator testing as a loose guide to choose the fans... Step5 is simply fitting it all in the case and thus irrelevant.

One of the issues is you can't account for the backpressure imposed by the case, which has knock on effect on airflow thru the rad... so you have to go overboard on the CFM vs what the graph tells you just to ensure that chassis backpressure isn't an issue... (ie: We can only guage performance based on the kit in free air. Soon as it's in a case, all the figures for thermal dissipation at blah airflow vs blah liqflow go out the window, unless we assume that whatever fans and quantity thereof that are attached to radiator pulling air into case are matched with the same exhausting air from the case... then it remains vaguely valid)

See http://www.over-clock.com/ivb/index.php?showtopic=20277

Where in the UK are you Bobo??

11-01-2007, 07:12 AM	#5
Marci Cooling Savant Join Date: May 2003 Location: Wakefield, West Yorkshire, UK Posts: 486	Re: How do you calculate how a rad performs based on the data? Basically same way as Jaydee... The only way I've ever managed to translate the data into useable is giving folks a "with this fan, this heatload, this flowrate, you can get your coolant to within XX degrees of ambient" based purely on the deltas Bill used in the Thermal Dissipation Charts. Coolant temp is all I'll aim people for... can't predict final CPU Temp / GPU Temp etc due to the differences in everyone's Thermal Resistance testing etc... The formula in the spreadsheet-source of Bill's PA Series graphs (at www.thermochill.com/PATesting) allows me to extrapolate different air > coolant deltas... standard graphs are at dT of 10... graphs HERE are extrapolated for a dT of 15... could recalc `em for an extrapolated dT of 5 too... but then the airflow required to cool the given heatload tends to be ridiculous when it comes to the noiselevels that airflow would present, hence not bothered with dT5 yet... S'all very loose and inaccurate but it's as good as I can explain... and folks seem to understand the concept... I summarised it into a 5-step procedure using combination of ExtremePSUCalc to (over-)estimate heatload, Martin's Flowrate calc to get the flowrate, Heat Dissipation graphs to roughly gauge the CFM required, then Cathar's Fan-on-Radiator testing as a loose guide to choose the fans... Step5 is simply fitting it all in the case and thus irrelevant. One of the issues is you can't account for the backpressure imposed by the case, which has knock on effect on airflow thru the rad... so you have to go overboard on the CFM vs what the graph tells you just to ensure that chassis backpressure isn't an issue... (ie: We can only guage performance based on the kit in free air. Soon as it's in a case, all the figures for thermal dissipation at blah airflow vs blah liqflow go out the window, unless we assume that whatever fans and quantity thereof that are attached to radiator pulling air into case are matched with the same exhausting air from the case... then it remains vaguely valid) See http://www.over-clock.com/ivb/index.php?showtopic=20277 Where in the UK are you Bobo?? __________________ www.minimotosidecars.org / www.thermochill.com / www.themusiccollective.co.uk Last edited by Marci; 11-02-2007 at 09:43 AM.