Pipeflow 3.0 pressure drop is a simple spreadsheet program that calculates pressure drop per 100 ft of pipe. This is very useful to plant personnel because it requires only six inputs. They are nominal pipe diameter in inches, pipe schedule, flow rate in gal/min, liquid viscosity in cP, density in lb/gal and pipe absolute roughness in feet.

There is no need to look up inside pipe diameters in a handbook because the program has a built-in lookup table. For every nominal pipe diameter and pipe schedule there is only one inside diameter. The program is valid for English nominal pipe diameters from 1/8 in. to 12 in. The following pipe schedules are also valid inputs: 5 to 160 and the stainless steel schedules 5S to 80S, XS and XXS.

The typical roughness factor for commercial steel is 0.00015 ft, although any other value can be input into the spreadsheet. In addition, the program calculates linear velocity in ft/s, Reynolds number, and Darcy friction factor.

The program is fully referenced and contains each formula in its entirety. Historical note is given to the original friction factor formula, the Colebrook-White Equation. The equation is implicit in f (friction factor) and therefore it is not used. ^{[1,2]}

Instead, the Churchill Equation ^{[3]} is used. This is full-regime equation that is valid for all Reynolds numbers whether they are laminar, turbulent or transition region. For comparison the Chen equation ^{[4]} is also used to calculate the Darcy friction factor and the associated pressure drop. All references, equations, instructions and tables are accessed through buttons imbedded in the spreadsheet as shown in the Figure.

Download the spreadsheet here: www.rccostello.com/PIPEFLOW3.xls

Costello routinely creates complex hydraulic models in ChemCad.

This article originally appeared in Chemical Engineering magazine August 1996 by Peter Silverberg.

References:

1. Gregory G.A., and Forgarasi M., Alternate to Standard Friction Factor Equation, Oil Gas J., 81, 13, April 1, 1985, p.120, 1985.

2. “Flow of Fluids”, Crane Technical Paper 410, 1979 edition.

3. Churchill, S.W., Friction Factor Equation Spans All Fluid Flow Regimes, Chem. Eng., 84, 24, Nov. 7, 1977, p.91, 1977.

4. Chen, N.H., An Explicit Equation for Friction Factor in Pipe, Ind. Eng. Chem, Fund., 18, p.296, 1979.