Two-phase flow in orifice plates and valves

The pressure drop that occurs when a two-phase flow passes through a pipeli ne component is usually found by calculating the single-phase value and mul tiplying it by a two-phase multiplier. Little or no consideration is given to what occurs within that component. For example, if the valve seat area i s sufficiently small, the fluid velocity will approach, or even reach, the critical velocity. In these circumstances, compressibility effects should b e accounted for-they rarely are. This study was initiated to develop a tech nique that would allow pressure drops to be predicted for pipe fittings, wh ether the flow is compressible or not, and to allow the critical mass flux to be estimated, thus allowing the method to be applied to the design of ve nting systems. The model developed can be used for all pipe fittings of the contraction-expansion type, like orifice plates and valves, up to and incl uding the choking point, provided the single-phase loss coefficient is know n.