Thermofluid Analysis of Ultra Low Power Hotplates for a MOX Gas Sensing Device

This work presents a full three-dimensional finite-element multiphysics simulation of the conjugate heat transfer for a gas sensing device composed by a two-element array of ultra low power (ULP) metal oxide semiconductor (MOX) sensors operated in a miniaturized sampling chamber. The heat equation in a solid, the Poisson equation for the electric potential and the incompressible Navier-Stokes and energy equations for a fluid have been solved in a coupled manner. Validation of the simulation results has been performed comparing the simulated power dissipated by the array with a set of experimental data under different operating conditions. A maximum relative error of less than 7% between the simulations and the experiments has been obtained without application of any fitting strategy on the physical properties. A negligible effect on the power dissipated by the sensor, in presence of volumetric fluxes in the sampling chamber, has been observed both numerically and experimentally. Finally, a real operational condition has been simulated and examined.