Viscosity Flow Correction for Small Control Valve Trim

Abstract

A valve sizing method is developed to permit the correct selection of the size of small flow control valve trim handling minute flowing quantities. Most valves such as these operate primarily in laminar or transitional flow regimes, with either gaseous or liquid fluids, due to the geometries involved. The proposed sizing method can be combined with existing turbulent flow equations by the establishment of a valve style modifier Fd which describes the correct relationship between the hydraulic diameter and the equivalent single orifice diameter of a specific valve trim, thereby permitting calculation of the correct Reynolds number for a given flow condition. Finally, a correction factor FR is used which permits necessary flow corrections when used in connection with the correct valve Reynolds number. This method appears to be reasonably accurate and validated to the extent that the experimental data permit.