Mirco Magnini

From thin liquid films to enhanced heat transfer in microchannel evaporators

The miniaturisation of electronic devices is pushing the demand for heat dissipation towards record-high values of Megawatts per square meter and above. Boiling flows offer the opportunity to meet this emerging demand, thanks to the removal of latent heat, efficient two-phase fluid dynamics and heat transfer mechanisms. A common heat sink configuration that maximises the heat exchange area is the microchannel evaporator, which is placed in direct contact with the device to be refrigerated. Here, the fluid flows confined within parallel channels and boils while efficiently carrying away the generated heat. These heat sinks have been widely investigated in the past decade using experimental techniques, however, progress in our fundamental understanding of two-phase boiling dynamics and heat transfer within microchannels remains limited because the small spatial and temporal scales of the flow make experimental analyses challenging. At Nottingham, we have developed direct numerical simulations techniques to study these fascinating flows, where the already non-trivial thin-film evolution in noncircular channels is further complicated by the dynamics triggered by boiling. In this talk, I will summarise our recent research efforts in this direction, covering (i) the isothermal dynamics of elongated bubbles in non-circular capillaries, (ii) coupling with heat transfer and boiling, and finally introducing (iii) the latest advances in our analysis of the evaporation microlayer in pool boiling.