Subcooled flow boiling in confined jet arrays: Experiments and development of new correlations

Hybrid cooling strategies that combine jet array impingement with confined channel flow have emerged as promising solutions for high-efficiency thermal management in compact, power-dense electronics. However, predictive tools for accurately estimating the average heat transfer coefficient and critical heat flux in such configurations—especially under subcooled boiling conditions—remain limited. This study experimentally investigates subcooled flow boiling heat transfer in confined jet array impingement cooling systems using the dielectric fluid FC-72, where circular jets impinge on a heated surface inside a narrow channel and exit through lateral outlets. Key parameters, including the number of jet holes, the distance from the jet hole outlet to the impingement surface, jet hole diameter, jet velocity, and inlet subcooling temperature, are systematically varied. High-speed visualization is also conducted to further examine vapor bubble dynamics within the confined channel. Based on 854 data points for average heat transfer coefficient and 59 data points for critical heat flux data, new correlations are developed by incorporating relevant dimensionless parameters that characterize boiling heat transfer performance. The proposed correlations exhibit significantly improved predictive accuracy over existing ones and can offer practical guidance for the thermal design and reliable operation of subcooled flow boiling systems employing confined jet arrays in high-heat-flux electronic applications.