Russell McMahon wrote:

> I'm seeking to find a formula which will allow me to very approximately
> establish the pneumatic resistance of smooth walled ducts at modest flow
> rates. I know Gargoyle knows but I can't convince it to tell me. I'm
> sure more than one of the people receiving this also know. =

> =

> This is essentially a HVAC application. Flow rates are in the few litres
> per second range. Temperatures are in the 0 - 30 C range. Wall material
> will ultimately be something smooth which may be a metal on some or all
> faces.

I have a paper source (the in Germany well-known Recknagel/Sprenger
"Taschenbuch f=FCr Heizung+Klimatechnik"). It contains a few empirical
diagrams, so for certain defined situations, I could look up the values.
This may then enable you to extend it further, as long as only parameters
change that have a known relationship (length, for example).

Gerhard

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