Piping Pressure Drop

A handy relationship for turbulent flow in commercial steel pipes is:

DP_F = W^1.8µ^0.2/20.000d^4.8r

where:

DPF	=	Frictional pressure loss, psi/lOO equivalent ft of Pipe
W	=	Flow rate, lb/hr
µ	=	Viscosity, cp
r	=	Density, lb/ft³
d	=	Internal pipe diameter, in.

This relationship holds for a Reynolds number range of 2,100 to 10⁶. For smooth tubes (assumed for heat exchanger tubeside pressure drop calculations), a constant of 23,000 should be used instead of 20,000.

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Source : Branan, Carl R. "Estimating Pressure Drop," Clzenzicnl Engineel-irzg, August 28. 1978.