An Experimental Study of Aluminum Pulsating Heat Pipes for Enhanced Cooling: Flow Characterization and the Effect of Aspect Ratio*

Managing high heat fluxes in electronic devices has become increasingly critical. In 2020, data centers in the USA used 100 billion liters of water annually for cooling, comparable to the water usage of Philadelphia. Future high-power electronic devices are expected to generate heat fluxes up to 5 kW/cm², exacerbating resource strain and complicating thermal management, particularly for NASA's essential systems such as planetary orbitary system, satellites etc. Conventional single-phase systems are inadequate for such high heat fluxes, necessitating two-phase thermal solutions like Pulsating Heat Pipes (PHPs), which have demonstrated superior heat extraction capabilities over traditional systems. This study explores aluminum flat PHPs with varying channel widths and turn numbers, while maintaining constant channel depth and total cross-sectional area with the purpose of optimizing current PHP designs. Experiments were conducted with filling ratios between 40% and 65% using pure ethanol. Instantaneous flow patterns were visualized with a high-speed camera and temperatures were captured at various locations using T-type thermocouples. Oscillatory flows and cooling improvement were observed for all configurations under study. The preliminary results indicate that the optimal aspect ratio is around 1.19. Our findings provide insights into the efficiency of aluminum flat PHPs for advanced electronic cooling, supporting effective thermal management in terrestrial and space applications.