Unsteady characteristics of a thermal microsystem

A novel integrated microsystem consisting of a heater, microchannels and distributed temperature sensors was successfully fabricated. The transient temperature behavior of the device was experimentally studied for a variety of power dissipation levels and forced convection flow rates, where DI water was used as the working fluid. Both heating-up and cooling-down time constants were determined for a pulsed current input. The device frequency response to a sinusoidal input voltage, with the device operating either in a single or in a two-phase mode, was characterized. The dependence of the resulting temperature average and amplitude on the input signal was studied for a variety of cycle conditions. It was found that, contrary to expectations, the heating-up time constant was larger than the cooling-down time constant. Furthermore, the periodic temperature field stabilized the system to avoid the occurrence of the dryout phenomenon.