Abstract: A high Cv bulk process valve, control system and method convey a process gas or liquid for manufacturing semiconductors through a fluid passage. The fluid passage contains an aerodynamically shaped expansion chamber within which a valve seat and a moveable poppet are arranged for opening and closing the fluid passage. The aerodynamically shaped expansion chamber includes a conically expanding entry and a conically contracting exit and is shaped such that the resistance to flow of the process gas or liquid through the fluid passage of the valve is very nearly the same as through a straight tubing having a cross-sectional area of an inlet to the valve and a length of the fluid passage through the valve. The valve can be added or subtracted from a gas or liquid control system with virtually no changes in pressure drop of flow restriction, when the valve is in the open position. The valve minimizes the energy consumed by valves in semiconductor gas systems.