Numerical simulation of liquid-liquid two-phase flow heat transfer in circular microchannels

The liquid-liquid two-phase flow heat transfer in circular microchannels is investigated through numerical simulation employing the level-set method. The heat transfer performance of the two-phase flow and the strength of the recirculating vortices are quantitatively characterized by defining the average Nusselt number within the unit cell and the pure rotational angular velocity of the fluid unit under the shear-free mode. The constant heat flux boundary condition was applied in the numerical simulations. The dynamic evolution of the Nusselt number and the distribution pattern of swirling intensity inside the unit cell are analyzed. The results indicate that increasing the size of microdroplets within a certain range and reducing the size of slugs contribute to improving the heat transfer performance. For two-phase flow systems with varying interfacial tensions, there exists an optimal capillary number that maximizes the heat transfer performance of the system. With different interfacial tensions, the heat transfer performance of two-phase flow exhibits various evolutionary trends with varying viscosity ratios. Increasing the interfacial tension promotes the enhancement of convective heat transfer in two-phase flow. Based on the research findings, empirical equations are proposed to describe the heat transfer performance of liquid-liquid two-phase flow.