E-fan airflow estimation method?

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mrob
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E-fan airflow estimation method?

Post by mrob »

Hi,
I recently installed a Derale dual fan system on my car. It didn't come with any airflow data for the fans, so I reached out to the fan manufacturer and they provided me with the fan data (CFM, in. H20 and amp draw) for the range of 0 in. H20 to 1.0 in. H20.

Looking at the fan data, I saw that the expected relationships between airflow, resistance and amperage: as resistance increases, airflow decreases and amperage increases. So this got me thinking, can I use the amperage to estimate the airflow and pressure drop through my radiator when the fan is installed? The amperage is easily measured, but the airflow and pressure drop aren't so easily measured without expensive instrumentation.

I know that the correct way to measure the airflow and pressure drop is by placing the radiator core in a laboratory test section with accurate flow and pressure measuring devices. What I'm looking for is a simpler way to estimate airflow and pressure drop using a DMM and the manufacturers fan data. Anybody have any thoughts on this? Or maybe some personal experience?
F-BIRD'88
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Re: E-fan airflow estimation method?

Post by F-BIRD'88 »

The supply voltage has to be kept constant to make comparisions.. Why not also track fan rpm installed VS free air rpm at a speced supply voltage, while checking amerage. Using a mechanics digital laser tach.
Many have a high-low max rpm memory.
Will read rpm from a white paint stripe on the fan blade.
mrob
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Re: E-fan airflow estimation method?

Post by mrob »

Thanks for the reply, F-Bird'88. Unfortunately, the fan manufacturer didn't supply the fan rpm. But your points about the supply voltage and tracking the fan rpm's are well taken. I can definitely see how a change in the supply voltage can affect the fan rpm, which will change the airflow and pressure drop through the radiator core.
What I'm trying to determine are estimated values of airflow and pressure drop using only fan curve (cfm, resistance and amperage). I'd like a more realistic airflow value than the one Derale published. I know that Derale uses the peak airflow which is nowhere near the actual flow when installed in the car.
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