Experiments on the Biporous Micropillar Array for Enhanced Heat Transfer Performance

A mathematical model has been developed in previous work to optimize the parameters of the biporous structures with micro channels among pillars to reduce the viscous force by shortening the liquid prorogation length inside porous media. In this paper, an experimental rig has been built to test the performance of the designed samples at ambient conditions according to the previous derived mathematical model. The pillar areas of the samples have been fabricated by photolithograph and Deep Reactive-Ion Etching (DRIE) with varied parameters for further comparisons. To simulate the concentrated heating of a working device and measure its temperature, a Pt heater and four Resistance Thermal Detectors (RTDs) have been fabricated by the electron beam deposition and lift-off process. The sample has been mounted horizontally to a water-proof sample holder, and the de-ionized water has been pumped into the evaporator through a reservoir by a syringe pump. By fine tuning the pumping rate, one can reach the minimum pumping rate while maintaining the water levels of the reservoir and the evaporator without drying out for a certain heating power. The mathematical model has be partially verified by the experimental results, which paves the way for the final design of the silicon vapor chamber.