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

• Insertion flowmeter without laminar or bypass elements tested for any kind of flow pattern.
• The analytical model qualitatively describes the temperature-flow curve for laminar flows.
• Unusual flow range for thermal flowmeters in liquids (from 0.5 L/min up to 19 L/min).
• Accuracy improved by combining multiple measurements and correcting the fluid temperature.
• An algorithm prevents the probe from damaging in zero-flow or empty pipe conditions.

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 to±0.7% 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 implementations is shown.