Design factors for “linear” ball valve: theoretical and experimental studies

Generic non-linear flow characteristics of the conventional ball valve limit the applications of flow modulation in fluid processes. This work presents the flow characteristics of fluid flowing through the conventional and modified ball valves for feasibility of a “linear” ball valve. Theoretical studies are discussed for determining explicit and implicit factors on the valve coefficient, which modulates the flow rate of fluid when the ball valve is operated in flow control processes. In experiment, the cross- sectional opening area at various opening degrees, the shape, and the location of the hole passage in valve ball are examined for complicated relations dependent to the flow rate of fluid. It can be concluded that those factors cause the modulation of flow rate when the ball is turned at different opening degree. In extended design of flow characteristics for linearity, they are to be taken into account.