Numerical investigation of flow boiling heat and mass transfer in distributed jet microchannels for lithium-ion battery cooling

Flow boiling in microchannels is a promising technique for thermal management of high-power lithium-ion batteries, yet accurate prediction of two-phase transport remains challenging due to unresolved nucleation dynamics and thin-film evaporation. In this study, a three-dimensional numerical framework is developed to investigate flow boiling heat and mass transfer in distributed jet microchannels using R-1233zd(E). A multi-site nucleation model is established based on the correlation between nucleation site density and activation temperature, while the conventional Volume of Fluid (VOF) model is enhanced through the incorporation of thin liquid film evaporation theory. The improved model significantly reduces the deviation between simulation and experiment, achieving agreement within 15 %. Using the validated model, three microchannel configurations co-current microchannel (CCM), counter-flow microchannel (CFM), and counter-flow interconnected microchannel (CFIM) are systematically compared. Results show that the CFIM design provides the most uniform vapor distribution and highest thermal performance, reducing the average base temperature by 22.6 % and the thermal resistance by 22.6 % relative to the CCM structure. Pressure fluctuation analysis further reveals that transient pressure spikes are closely associated with rapid vapor slug growth and outlet venting phenomena. The present findings provide quantitative insights into microscale two-phase transport and offer guidelines for designing high-performance microchannel cooling plates for next-generation battery thermal management systems.