Characterization of the multiphase flow in microfluidic pulsating heat pipes: the effect of channel geometry and surface properties

As electronic devices become more powerful, managing high heat fluxes exceeding 1 kW/cm² has become critical. Conventional single-phase cooling methods often come short of performance, particularly in space systems where reliability and weight are crucial. Pulsating heat pipes (PHPs), among others, have emerged as a promising solution for their compact form factor and efficient heat transport without moving parts. However, PHP performance is highly sensitive to geometry, orientation, and operating conditions and our understanding of its basic working principles is still limited, underscoring the need for further investigation.

This study investigates the performance of microfluidic PHPs with an emphasis on revealing the underlying flow physics and the effects of different parameters that govern its performance. A series of PHPs are fabricated via various methods including machining, 3D printing and microfabrication techniques. High-speed flow visualization and PIV are used to extract oscillation frequencies and characterize flow dynamics, whereas comparative thermal analyses are performed by means of control variables. The preliminary results indicate that an optimal channel aspect ratio exists for maximized heat transfer and that surface wetting property plays a crucial role. These findings support the advancement of flat PHPs as a compact and efficient thermal management solution in high heat flux applications.