Numerical simulation of flow boiling in microchannels: bubble growth, detachment and coalescence

Flow Boiling heat transfer within micro-channels has been a subject of extensive investigation during the last decades. Due to the underlined complexity, the development of comprehensive correlations and/or models for flow boiling has not been possible so far. However, more recently, numerical simulations have been proven being capable of reliably predicting bubble dynamics and heat transfer characteristics. Heat transfer and phasechange due to evaporation and/or condensation are coupled with a previously improved and validated, Volume Of Fluid (VOF) model for adiabatic bubble dynamics. Initially the model is validated with an existing analytical solution and with literature available experimental results of pool boiling with an excellent degree of convergence. In the present paper, the proposed VOF model is further applied for 3D numerical simulations of flow boiling in micro-channels, with single and multiple nucleation sites identifying some interesting observations regarding the bubble growth and detachment characteristics within the liquid cross-flow as well as regarding the coalescence of bubbles detaching from different nucleation sites. The analysis of the numerical results reveals that the proposed numerical model constitutes a quite promising tool for the investigation of the complex sub-processes which occur during flow boiling in micro-channels.