Dynamic similarity for non-newtonian fluids in globe valves

Previous experimental work in globe valves has mainly been conducted over a narrow range of laminar or turbulent flow. The work available in laminar flow has not been conducted in geometrically similar valves, hence dynamic similarity could not be established-a critical precursor to practical engineering hydraulic design. In this work various Newtonian and non-Newtonian fluids, including viscoplastic fluids, were tested in three globe valves (with circular plug disk) of 15mm, 25mmand 40mmnominal diameters on a Balanced Beam Tube Viscometer (BBTV). A single constant was obtained in laminar flow to determine the loss coefficient for all the sizes of valves and types of fluids tested in the valve, indicating that dynamic similarity had been achieved. Consequently a correlation could be developed to determine the loss coefficient in globe valves in both the fully open and half open positions. Dynamic similarity was obtained using a Reynolds number that accounted for the fluid rheology, specifically the yield stress