Effects of upstream pipe fittings on the performance of orifice and conical flowmeters

Abstract

It is difficult to get high accuracy over a broad measurement range from a flowmeter operating in ideal conditions, but when the device is placed in a hostile environment with highly disturbed flow profiles involving swirl caused by various pipe fittings such as pipe bends installed upstream of metering element, the task becomes even tougher. In this regard, the conical flowmeter seems to fare better than other pressure differential devices. In the present study, experiments were conducted to investigate the effect of upstream pipe fittings such as a single 90° mitre bend, double 90° mitre bends in-plane and double 90° mitre bends out-of-plane on the performance of a conical flowmeter and orifice meter. These measurements are carried out for Reynolds numbers ranging from 30000 to 494000 for a constant β ratio of 0.75 with air as the working medium. Further, static pressure distributions downstream of the orifice meter and conical flowmeter are measured to estimate the irrecoverable pressure drop due to the flowmeter in the line. Results indicate that the conical flowmeter is less sensitive to swirl when compared with the orifice meter. Further, the irrecoverable pressure drop in the conical flowmeter is 50% less than that for the orifice meter.