The Use of a Self-Heating Thermistor for Flow Rate Measurement


Class: BE310
Group: M4
Members: Alan Doucette, Adam Furman, Phillip Matsunaga, Lisa Toppin

Date: May, 2002

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Abstract:
In this experiment, a liquid flow meter was developed using the self-heating behavior of a thermistor.  Using principles taken from thermodilution experiments, the phenomenon of self-heating could be harnessed to measure flow rate.  The thermistor’s dissipation factor, DF, was determined by varying the Reynolds number of the fluid flow.  The set up of the experiment mimicked a thermal dispersion flow meter that allowed for the determination of the fluid’s volumetric flow rate by measuring the change in temperature of the thermistor caused by a specific power dissipation.  A linear calibration was found by plotting: According to predictions outlined in the theory section, the straight-line equation should be y = mx + b, where m = 3.778 x 10-3 W/K and b = 6.852 x 10-3 W/K and the experimental data produced the linear equation with m = 3.7 x 10-3 W/K and b = 0.021 W/K.  The nearly identical slope shows that the collected data follows the same trend as the theory predicts.  While slight discrepancies are apparent, especially in the y intercepts, there is good agreement between the slopes.