Critical heat fluxes for subcooled flow boiling in optimised microchannels

Critical heat fluxes (departure from nucleate boiling, DNB) for optimised rectangular microchannels were computed by carrying out simulations using computational fluid dynamics (CFD, ANSYS) non-equilibrium boiling model (the model is an extension of heat flux partitioning model for modelling up to departure from nucleate boiling) for subcooled flow boiling, at velocity ranges of 1.0-1.5 and 1.5-2.0 m/s and heat fluxes of 300 to 500 W/cm2. The flow was highly subcooled at inlet temperature of 25°C using deionised water as the cooling fluid and aluminium as the heat sink material. The results showed that the microchannels can be operated beyond the heat fluxes that they were optimised, up to their critical heat fluxes before the onset of departure from nucleate boiling or CHF. The numerical code for heat flux partitioning model (RPI) was validated by the available experimental data and the agreement showed the capability of the model to predict accurately subcooled flow boiling in microchannels.