Numerical simulation of microchannel flow boiling and critical heat flux under rolling motion

In this paper, microchannel flow boiling heat transfer and critical heat flux (CHF) are numerically characterized under both static and rolling conditions. The volume of fluid (VOF) based numerical model of a rectangular microchannel with the dimension of 4 x 400 mm is established. The additional force induced by rolling motion is loaded via a user defined function (UDF). Rolling amplitude and rolling period vary in the range of 10-20 degrees and 1 similar to 2 s, respectively. The results demonstrate that bubble flow, slug flow, stretch bubble flow and annular flow are observed under static conditions. However, under rolling conditions, bubbles are more difficult to agglomerate and coalesce under the influence of additional forces. Rolling motion maximumly deteriorates CHF by 81.1% and wall temperature by 18.8%, respectively. Moreover, CHF decreases with the increase of rolling period while increases with the increase of rolling amplitude. The purpose of this research is to understand the microchannel CHF triggering mechanism under rolling conditions to aid in marine heat exchanger design.