Insertion calorimetric flowmeter for liquids with multiple temperature sensors to improve measurement by redundancy

Abstract

In this paper a thermal flowmeter based on the calorimetric principle is reported and analytically modeled. The flow is measured without using any kind of laminar or bypass elements and it has been tested for laminar, transitional and turbulent flow patterns. It contains four temperature sensors. Three of them are placed downstream and the fourth upstream. Results showed that the model qualitatively describes the relationship between temperature and mean velocity in laminar flows. The meter accuracy is increased by combining the flow estimations given by three downstream sensors (redundancy of measurements) and by continuously correcting the dependency that the calorimetric method shows on fluid temperature. Experimental results, using water as fluid, make the accuracy rate of the instrument equal to70.7% FS in a range between 0.5 L/min and 19 L/min, which is not a usual range for thermal flowmeters in liquids. Finally, an algorithm to prevent the probe from damaging in practical im plementations is shown.