Lattice Boltzmann mesoscopic modeling of flow boiling heat transfer processes in a microchannel

Abstract Microchannel flow boiling has received increasing attention for its high heat dissipation intensity with a small temperature difference. In the present study, a multi-relaxation-time (MRT) phase change lattice Boltzmann model is employed to investigate the flow boiling heat transfer processes in a vertical microchannel under constant heat flux boundary conditions. The bubble dynamic behavior including nucleation, growth, slide, coalescence and departure is obtained and the periodic variations of wall superheat and heat transfer coefficient are evaluated using the Jacob (Ja) number and Nusselt (Nu) number. It is demonstrated that the cavity microstructure on the heating surface can enhance the flow boiling heat transfer, further the cavity height and cavity distance are optimized with single-cavity model and multi-cavity model, respectively. Phase change heat transfer and flow boiling curves from single-phase forced convection, nucleate boiling regime, transition boiling regime to stable film boiling regime are numerically predicted for both the single-cavity structure and multi-cavity structures. The simulation results show that increasing Reynolds (Re) number accelerates the bubble departure frequency and intensifies the external forced convection, thereby achieving enhanced flow boiling heat transfer performance. These findings advance our understanding of the bubble dynamics and heat transfer mechanisms in the microchannel flow boiling processes.