Pipe Flow Expert User Guide
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Glossary 201 Glossary Term Description Absolute pressure Pressure measured with respect to zero pressure. Atmosphere A standard atmospheric pressure of 1.01325 bar a or 14.696 psi a. Centipoise Absolute viscosity of a fluid expressed in Pa • s x 10 -3 Centistokes Kinematic viscosity of a fluid expressed in m²/s x 10 -6 Note: Pipe Flow Expert requires fluid viscosity to be entered in Centipoise. Colebrook-White equation An equation used to calculate accurate friction factors from the internal diameter and internal roughness of a pipe and the Reynolds number for the flow conditions. Darcy-Weisbach equation An equation used to calculate the frictional head loss due to fluid flow from the friction factor, the length and diameter of the pipe, the velocity of the fluid and the gravitational constant. Demand flow The In-Flow entering the system or the Out-Flow leaving the system. Demand pressure The pressure at a point of exit from the system. Discharge Out-Flow leaving the system. Dynamic viscosity The absolute viscosity of a fluid. Friction factor A factor to be used in the Darcy-Weisbach equation. Either calculated from the Colebrook-White equation or read from the Moody diagram. Elevation The height above sea level of a node or tank. End pressure The pressure at a point where fluid leaves the system. Fixed pressure A static pressure loss which is independent of the flow rate. Fluid head The resistance to flow expressed in height of fluid as a motive force. Gage pressure Pressure measured with respect to atmospheric pressure. Hydraulic grade line The pressure at a point in the system expressed in height of fluid plus the elevation above sea level of the node or the tank. in Hg Height of a column of mercury in a barometer expressed in inches. K value Coefficient of frictional loss through valve or pipe fittings. Kinematic viscosity The absolute viscosity of a fluid divided by the fluid density. Moody diagram A graphical representation of the relationship between Reynolds number, relative roughness and Friction factor. mm Hg Height of a column of mercury in a barometer expressed in millimeters. NPSHa Net Positive Such Head available. NPSHr Net Positive Such Head requirement. Pressure loss The friction loss due to fluid flow expressed in fluid head or Gage pressure. Pump head The motive force developed by a pump expressed in height of fluid. (Pump performance graphs usually show pump head for water). Relative roughness A dimensionless number expressing the internal roughness of a pipe divided by the internal diameter of a pipe. Reynolds number A dimensionless number derived from the fluid velocity, the internal diameter of the pipe and the Kinematic viscosity of the fluid. Supply In-Flow entering the system. Vapor pressure The absolute pressure at which a liquid will start to evaporate. Viscosity A measure of a fluid‘s resistance to flow. See absolute viscosity and Kinematic viscosity. |