The function of differential pressure flowmeter
The differential pressure flowmeter, like the orifice flowmeter, nozzle flowmeter, and venturi tube flowmeter, is used for pipe flow measurement. For each type, a constriction (like an orifice plate) in the flow path causes a pressure drop across the meter. The pressure drop can be measured and correlated with flow rate.
The term pipe flow rate is often used to refer to flow rate for any closed conduit flow under pressure. The closed conduit is often circular, but may also be square or rectangular, such as a heating duct. The other major category of flow is open channel flow, which occurs when there is a free liquid surface open to atmospheric pressure. Pipe flow measurement is often done with a differential pressure flow meter like the orifice flowmeter, nozzle flowmeter, and venturi tube flowmeter.