On 9/12/2010 4:25 PM, Scott Townley wrote:
> The general recommendation for checking forced-air cooling system
> performance is to use a manometer to check back pressure.
> I wonder, isn't the "true" test the CFM in the exhaust? After all, if the
> blower can't "push" through the tube/socket back pressure, then the net
> result is not enough CFM.
> \
IF you have the required pressure drop across the tube you WILL have the
required flow.
The dynamics are much the same as ohms law. IF you have the pressure
(voltage) across a resistor (tube) you will have the flow (current)
It's pure straight forward physics.
OTOH if you use a vane or some method of measuring the output flow and
it is correct, then the input pressure has to be as well.
If the input pressure rises above normal, it's an indication that the
area for the flow has been reduced...plugged, or partially so.
Just think of the cooling system as a series resistive circuit.
73
Roger (K8RI)
> I ask that because while I don't have a manometer (though that is not
> insurmountable by any means), I do have an anemometer calibrated to read
> CFM. It would seem that a guaranteed test is to be able to measure the
> recommended CFM in the exhaust air, if the exhaust is sufficiently ducted.
> Thoughts?
>
>
> Scott Townley NX7U
> Gilbert, AZ DM43di
> mailto:nx7u@cox.net
> http://members.cox.net/nx7u
>
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