Flow-jet composite boiling on microstructured surfaces in microgravity: An experimental study aboard the China Space Station

The increasing demand for high heat flux dissipation poses critical challenges for space thermal management, where the absence of buoyancy under microgravity fundamentally alters boiling heat transfer mechanisms. In this study, experiments were conducted on the China Space Station to systematically investigate boiling heat transfer on a uniform micro-pin-fins surface under the coupled effects of microgravity and microscale structures. For the first time, the enhancement mechanism of flow-jet impingement composite boiling under long-duration microgravity is revealed. Results show that under pure flow boiling conditions, the micro-pin-fins surface significantly outperforms the smooth surface, with the critical heat flux (CHF) and heat transfer coefficient enhanced by up to 51.8% and 60.7%, respectively. With the introduction of jet impingement, the heat transfer performance is further improved, with the maximum absolute value of CHF reaching 80.04 W/cm 2 . This enhancement originates from the synergistic interaction between the micro-structured surface and momentum-driven convection. The micro-pin-fins array provides abundant nucleation sites and strong capillary wicking, while shear flow and jet impingement promote rapid bubble detachment and breakup, effectively suppressing bubble accumulation under microgravity. Gravity comparison reveals that the micro-pin-fins surface exhibits slightly higher CHF under terrestrial conditions, whereas the smooth surface shows the opposite trend. These findings provide key insights into microgravity boiling mechanisms and offer guidance for the design of advanced two-phase thermal management systems for space applications.