The Response of a Heat Loss Flowmeter in a Water Pipe Under Changing Flow Conditions

Abstract

A heat loss flowmeter for measuring the volume flow rate of water in real time ( $t)$ was formed using two thick film segmented thermistors, range constant voltage (RCV) power supply, acquisition card, PC, and software. The input water temperature $T_{w}(t)$ was measured by a cold thermistor, while the water flow rate $Q(t)$ was determined using the heat loss principle by measuring the self-heated thermistor current $I(t)$ . The flowmeter inertia, stability, and accuracy were measured and analyzed on a flowmeter prototype in real-time and real conditions on the water mains. The flowmeter response was measured for different durations of step input water flow-out functions and intervals between steps. An independent ultrasonic flowmeter was connected in series with the thermal flowmeter to measure the ordered input water flow functions. The realized intelligent functions in real time were: measuring the input water temperature $T_{w}(t)$ and self-heating temperature $T_{s}(t)$ , auto-selection of RCV supply voltage $U(T_{w})$ , determination and modeling of the water flow rate in real time $Q(t)$ , determination of the water volume $V(t)$ , and determination of the thermal gradient on the self-heating thermistor as a water flow indicator $\Delta R_{s}(t)$ .