Investigation on the calibration for the membrane type heat flux sensor using micro heater

Abstract

This paper presents the calibration accuracy of the membrane type heat flux sensor using micro heater. The directional heat flow rate into the thermal sensor is simulated with FEM to estimate the heat flux from micro heater for calibration. Thin film thermopile which is fabricated on the dielectric membrane directly converts the temperature difference between hot and cold junctions of thermopile into heat flux signal created by the thermoelectric effect. However, symmetric design of thermopile is restricted to only measure x-directional heat flow rate, when heat also propagates through y direction via heat conduction and z direction with convection. Therefore, it is highly needed to investigate how amount of heat from the micro heater contributes to the calibration of heat flux sensor. In the case of the calibration using micro heater, heat conduction through the membrane dominates heat flow. Thus, 97% of heat flow from micro heater propagates through the thermopile and generates 1.038 V/W of sensitivity that was estimated by the simulated model as 1.066 V/W. On the other hand, in case of water filled micro channel, 87% of heat flow reaches to thermopile and estimated 0.392 V/W of sensitivity. This heat loss leads to the inaccurate calibration as well as the lowered sensitivity.