Critical flow venturis (CFVs) can be used to measure flow under transient pressure and flow conditions with uncertainties of 0.13 % or less (95 % confidence level). Blow-down tests transferred 630 g of nitrogen during a 100 s interval from an unregulated cylinder (initially at 10 MPa) through a heat exchanger and a CFV into a known collection volume. Fast pressure and temperature sensors were used to calculate the CFV flow. The integrated CFV mass flows, , averaged 0.04 % smaller than the mass V of the collected gas. The heat exchanger was essential to the excellent agreement; without it, the percentage difference between and V was 0.38 %. We conclude that even under transient conditions, a properly instrumented CFV can be used as a reference flowmeter to evaluate other flowmeter types or to test gaseous fuel dispensers in the field.
Citation: Measurement Science & Technology
Pub Type: Journals
blow-down test, critical flow venture, critical nozzle, fuel dispenser, transient flow