Unsteady characteristics of a thermal microsystem

A novel integrated microsystem consisting of a heater, microchannels and di stributed temperature sensors was successfully fabricated. The transient te mperature behavior of the device was experimentally studied for a variety o f power dissipation levels and forced convection flow rates, where DI water was used as the working fluid. Both heating-up and cooling-down time const ants were determined for a pulsed current input. The device frequency respo nse to a sinusoidal input voltage, with the device operating either in a si ngle or in a two-phase mode, was characterized. The dependence of the resul ting 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 constan t. Furthermore, the periodic temperature field stabilized the system to avo id the occurrence of the dryout phenomenon. (C) 2000 Elsevier Science S.A. All rights reserved.