Fabrication and characterization of an integrated thermal microsystem

A thermal microsystem, integrated with pressure and temperature microsensors, is fabricated to study convective boiling under uniform heat flux boundary condition. Utilizing a wafer bond and etch back technology, the heat source, temperature and pressure sensors are separated from the fluid flow by a membrane only 1.5/spl mu/m in thickness; thus, allowing experimentally good control of the thermal boundary conditions. Temperature distributions for various input power levels have been measured to obtain the boiling curves. The conditions corresponding to the onset of two phase flow, with boiling plateau, and the critical heat flux (CHF) are clearly distinguishable. Simultaneously, time-dependent pressure signals have also been recorded. In single liquid phase flow, the pressure is constant with time. However, in two phase flow, strong pressure fluctuations occur with certain frequencies. The qualitative visualizations of the evolving flow patterns have been correlated with the quantitative temperature and pressure measurements.