Numerical optimization of bevel angle in conical entrance multihole plates to reduce pressure losses

Abstract

Multihole plates are employed in many fluid flow systems with purpose to eliminate the issues arisen from distorted flows created by pipe fittings or to control pressure or flow rate in the line by its high pressure loss. However, high pressure losses are undesirable in the flow system since causes lots of pump power consumption. Therefore, to minimize its high pressure loss, conical entrance multihole plate type was considered in this study and optimized numerically by varying orifice inlet conical angle.

Multihole plate inside a horizontal straight circular pipe with standard length requirements upstream and downstream were tested numerically with steady adiabatic and isothermal water flow over a wide range of Reynolds numbers between 2967 and 847728 utilizing time averaged turbulent flow equations. Published empirical data and formulas validate the numerical results. Upon plots of flow coefficients, an optimum conical angle around 20° which makes the pressure loss minimum was determined as regardless of Reynolds number. In comparison to multihole plate with sharp-edged orifice inlets, pressure loss was reduced by 48–55 % at this optimum conical angle, about 25 percent more efficient than 45° conical angle as a familiarized one. Reynolds number independence region starts at very low Reynolds number for MO plate with conical angles below 30°, nearly eight times smaller than one for 45° conical angle. Vena contracta velocity was found responsible on the turbulence production in the orifice flow expansion section which leads to most pressure loss caused by MO plate drag. Therefore, orifice conical geometry reduced pressure loss by yielding lower Vena contracta velocities compared to sharp square-edged orifices.