Flow rate measuring device

Abstract

A flow rate metering device having an inlet plenum chamber which accepts fluid flow of any velocity distribution and disperses that fluid to a homogeneous, essentially zero velocity fluid body from which a flow nozzle draws such zero velocity fluid and accelerates it therethrough to obtain a pressure drop. By measuring the pressure at selected locations upstream and downstream from the nozzle inlet, fluid flow rate through the nozzle can be metered by reference to conventional pressure differential correlations. The upstream pressure tap is preferably in the plenum chamber near the point where fluid velocity is near zero and the downstream pressure tap is preferably disposed in either of two locations: the downstream face of the flow nozzle or through the wall of a conduit into which the differential pressure nozzle discharges. Disposed within the plenum chamber is a flow deceleration device which augments the plenum chamber's inherent capability of reducing entering fluid flow velocity to substantially zero. The flow deceleration device is preferably located in a low velocity region of the plenum chamber so as to minimize pressure drop therethrough. The cross-sectional flow area of the plenum chamber is preferably at least nine times that of its inlet port and the length of the plenum chamber in the direction of normal fluid flow is preferably at least three times the inlet port's equivalent diameter.