Visual experimental study on subcooled boiling characteristics in a manifold jet microchannel heat sink

Jet microchannel cooling technology, integrating the compactness of microchannel architectures with the high efficiency of jet impingement, presents a promising approach for extreme heat flux thermal management. Current research remains predominantly confined to single-phase heat transfer owing to limited understanding of gas–liquid interfacial dynamics and phase-change mechanisms within these systems. To bridge this gap, a two-phase flow visualization platform was developed to systematically investigate the thermal performance and flow resistance of a manifold jet microchannel heat sink operating under subcooled boiling. Analysis of bubble dynamics and surface temperature revealed a wall temperature reduction of 0.3∼2.1 °C (termed “temperature overshoot”) upon reaching the onset of nucleate boiling (ONB), with the overshoot magnitude increasing proportionally with higher flow rates and lower inlet liquid temperatures. The impacts of operational parameters (inlet flow rate, temperature, and heat flux) and flow pattern transitions on boiling heat transfer and flow resistance were rigorously characterized. Notably, periodic boiling cycles (100∼180 ms duration) near the ONB threshold were identified, exhibiting progressive temporal compression under elevated flux or reduced inlet temperatures. Furthermore, distinct bubble behaviors linked to two-phase flow patterns were correlated with significant alterations in thermal resistance and pressure drop. These findings provide fundamental insights into phase-change mechanisms in microconfined spaces, advancing the rational design of high-flux thermal management systems.