Comparison of orifice and slotted plate flowmeters

Abstract

The performance of a standard β = 0.50 orifice flowmeter is compared to the same flowmeter with a slotted orifice plate replacing the standard orifice plate. The slotted orifice plate has the same total open area as the standard plate and consists of three concentric rings, each of which contains several radial slots. The flow upstream of both orifice plates in preconditioned using a concentric pipe device to produce a wide range of axial velocity profiles without swirl. The discharge coefficient of the standard plate varies from the base value by −1% to +6%, while that of the slotted orifice plate varies by only ±0.25%. When swirl is generated upstream of the orifice plates, the discharge coefficients vary by 5% and 2% for the standard and slotted orifice plates, respectively. These data indicate that the slotted orifice flowmeter is superior to the standard orifice flowmeter in maintaining its calibration over a wide range of inlet flow conditions. The slotted orifice plate can be a ‘drop in’ replacement for a standard orifice plate.