share your knowledge and Sent to:

Tuesday, August 26, 2008

Liquid Pipe Flow: Pressure Drop Calculation


Flow Of Liquid & Compressed Gases Through Circular Pipe
A common engineering problem to be able to determine the losses (analysis), or velocity (prediction) or the conduit size (design) of a piping system. Flow in a pipe is characterized by 7 parameters: Fluid viscosity & specific gravity, Pipe internal diameter, roughness & length, Flow rate/velocity & head loss/pressure drop. Based on which of the parameters are known, four types of computational problems are identified: namely the Calculation of i) Pressure drop, ii) Flow rate, iii) the Pipe internal diameter and iv) Pipe length. This task is accomplished by appropriate rearrangement, substitution and iterative solution of the following Equations:

Reynolds Number Re=VD/ν

Re = Reynolds Number
Q = average flow rate
V = average flow velocity
γ = fluid specific gravity
ν = kinetic viscosity, centistokes
D = pipe inside diameter
L = pipe length
ε = absolute internal pipe roughness
ƒ = friction factor
ΔZ = change in elevation
h = pressure head
hf = head loss due to pipe friction
Lm = head losses due to fittings, valves, etc(length equivalent)
P = pressure
g = gravitation acceleration

* Menon ES; Piping Calculations Manual; McGraw Hill, New York, 2005.
* Hicks TG; Mechanical Engineering Formulas, Pocket Guide; McGraw Hill, New York, 2003, Chapter 10.
* Menon ES; Liquid Pipeline Hydraulics; Marcel Dekker, Inc, New York, 2004.
* Hicks TG (Editor); Handbook Of Mechanical Engineering Calculations; McGraw Hill, New York, 1998, Section 8.

No comments: