Effect of Joule heating and temperature‐dependent zeta potential on electroosmotic flow measurements in calorimetric flow sensors

This work reports a theoretical investigation of the effect of Joule heating and temperature‐dependent zeta potential on the electroosmotic flow measurements in calorimetric flow sensing. Joule heating resulting from the applied electric field in electroosmotic flow increases the temperature of the liquid inside the sensor and, consequently, modifies the sensor performance. The model presented in this paper considers temperature dependence of the wall zeta potential on the sensor characteristics. Additionally, all liquid properties such as density, viscosity, relative permittivity, specific heat, thermal conductivity, and electrical conductivity are taken as temperature‐dependent properties. A comparison between the characteristics of the modelled sensor in the presence and absence of Joule heating is presented. The effect of heater power on sensor characteristics is also discussed. Simulation results reveal that Joule heating and temperature dependence of zeta potential have a significant effect on the behaviour of calorimetric flow sensors, which must be considered when this type of sensor is used to measure electroosmotic flow. Temperature dependence of zeta potential, in particular, affected the velocity distribution inside the sensor considerably.