Analysis of the thermal flowmeter operating from a pulsed-heat injection source

Abstract

An analytical relation for the thermal flowmeter, operated in a closed- loop form, is derived in terms of increase in heat injection rate and mass flow rate over the laminar as well as turbulent flow ranges. It is pointed out in the analysis that a thermal flow transducer may be characterized by two easily measurable parameters. A description is given of the 1/4 in thermal flowmeter, operated from a small pulsed-heat source, which can measure water flow rates from 50 lb to h-1 to 1500 lb h-1. The analytical relation is verified against the output of this flowmeter and it is shown that the pulsed-heat source improves the flowmeter output characteristics compared with the DC heat source and provides a signal whose frequency depends upon the flow rate.