Experimental Investigation of Silicon-Based Micro-Pulsating Heat Pipe for Cooling Electronics

Abstract

A simultaneous temperature measurement and flow visualization experiment was performed to investigate the thermal and flow behaviors of a silicon-based micro-pulsating heat pipe (micro-PHP) with trapezoidal microchannels with a hydraulic diameter of 352 μm. FC-72 and R113 were used as working fluids. Variations in temperature versus time at different locations of the micro-PHP under different power inputs and typical flow patterns in microchannels were recorded. The evaporator wall temperature, or the maximum localized temperature, of the micro-PHP at moderate filling ratios was measured and compared to those derived from the empty microdevice (0% filling ratio). Experimental results showed that a micro-PHP embedded in a semiconductor chip could significantly decrease the maximum localized temperature. At a power input of 6.3 W, reductions in the evaporator wall temperature of about 42.1°C (or 34.1%) and 41.9°C (or 33.9%) were obtained for the micro-PHP charged with R113 at filling ratios of 41 and 58%, respectively. When the micro-PHP charged with FC-72, a maximum power input of about 9.5 W associated with a heat flux up to 10.7 W/cm2 was reached at a moderate rise in wall temperature of the evaporator. The visualization study demonstrated that the evaporation, adiabatic, and condensation sections of the micro-PHP were largely occupied by annular, slug, and slug–bubbly flows, respectively, at a steady state characterized by sustained self-exciting oscillations of working fluid. However, no local nucleate boiling was detected in the micro-PHP at the power input range, which was different from the results reported for traditional PHPs.