Using the K, Cv, Kv Calculator

by Jeff Sines, Senior Product Engineer

Version 16.1 of PIPE-FLO Professional, PIPE-FLO Professional Lite, and Flow of Fluids introduced the K, Cv, Kv Calculator in the modeling of installed valves and fittings of a pipeline. A value of the Resistance Coefficient (K), Flow Coefficient (Cv), or Flow Factor (Kv) can be calculated and added to a pipeline as a Fixed K, Fixed Cv, or Fixed Kv fitting. The value can be calculated from user-entered Flow Rate and Pressure Drop measurements or approximations, the fluid density in the pipeline, and flow area (calculated from the diameter) of the pipeline. For example, using a fluid density of 62.37 lb/ft3, the flow area of a 4" NPS pipe (4.026 inches), a flow rate of 400 gpm, and a pressure drop of 3.5 psi, the equivalent values are:

• Resistance Coefficient K = 5.116
• Flow Coefficient Cv = 213.8
• Flow Factor Kv = 184.9

Using the Pressure Boundaries in PIPE-FLO to set a pressure drop of 3.5 psi (60 psig inlet, 56.5 psig outlet), the program calculates the flow rate that satisfies this pressure difference given the fluid and pipe properties, which is the flow rate that was used to calculate the coefficients for a 3.5 psi pressure drop, or 400 gpm for each pipe with an installed Fixed K, Fixed Cv, and Fixed Kv. 