Subcooled two-phase flow boiling in a microchannel heat sink: comparison of conventional numerical models

Subcooled flow boiling in multi-microchannels can be used as an efficient thermal management approach in compact electrical devices. Highly subcooled flow boiling of HFE 7100 is studied in two microchannel heat sinks to choose a proper numerical model for simulating boiling flows in microchannels. Results of five different numerical models, including Volume of Fluid (VOF), Eulerian boiling, Eulerian Lee, Eulerian thermal phase change, and mixture models, were compared with experimental data. ANSYS Fluent was used as the numerical tool to solve three-dimensional governing equations. Results were obtained in the steady-state condition of the transient solution. The average wall temperature reached a steady state in all models except in Eulerian boiling and mixture models. It was found that Eulerian thermal phase change and VOF models predicted microchannel’s bottom wall average temperature with less than 2% error. VOF model predicted flow boiling regime as it was reported in the experimental research and boiling curves. Velocity distribution over microchannel height was investigated, and it was observed that after the onset of nucleate boiling, the velocity profile becomes asymmetrical. Also, in the two-phase regions, each phase had a different velocity magnitude and distribution. Based on flow regime and temperature results, which were compared with experimental data, VOF model was recommended as the best model to simulate flow boiling in microchannels at the working conditions of this research. Furthermore, subcooled flow boiling’s capability to be used in thermal management systems was proved while observing temperature distribution over computational domain.

Keywords:

Subcooled flow boiling , Microchannel , Heat Sink , CFD , VOF model