TABLE OF CONTENTS The main purpose of piping systems is to transport fluids from one location to another. Numerous standard fluid flow equations are used to calculate the flow and pressure drop of pipe and fittings. Each equation is unique and might have limitations associated with its use. This chapter will describe many of the various equations used for fluid flow calculations, with a focus on plastic piping systems. It is important that the engineer uses an equation that is appropriate for the flow condition being analyzed.
A fluid is any liquid or gas that cannot sustain its shape when subjected to a tangential or shearing force when at rest. This continuous and irrecoverable change of position of one part of the material relative to another part when under shear stress constitutes flow, a characteristic property of fluids. Liquids and gases are classified together as fluids because, over a wide range of situations, they have identical equations of motion and exhibit the same flow phenomena. Liquids change their volume slightly with significant variations in pressure, while gases tend to expand and completely fill any container. With gases, a change in pressure is accompanied by a change in volume.
The following variables and nomenclature are used throughout the liquid flow section:
| C w | = | Hazen-Williams Coefficient |
| D | = | Inside pipe diameter, ft |
| d | = | Inside pipe diameter, in. |
| f | = | Friction factor, dimensionless |
| g | = | Gravitational acceleration, ft/sec 2 |
| g c | = | Gravitational constant, 32.174 ft/sec 2 |
| h p | = | Head... |
