Flow-Pattern Based Heat Transfer Correlations for Stable Flow Boiling in Micro/Minichannels

Flow-pattern based heat transfer correlations for elongated bubbly flow and annular flow in stable flow boiling micro/minichannels were developed separately based on a collected micro/minichannel heat-transfer database by using an improved conventional-to-micro/minichannel threshold Bo = 4 and BoRe(l)(0.5) = 200, where Bo is the Bond number and Rel is the liquid Reynolds number. As significant disagreement in experimental trends and heat transfer mechanisms was reported for flow boiling in micro/minichannels in the literature, it is not possible to explain the discrepancy and predict all data points by a single correlation without considering the different flow patterns. The newly developed flow-pattern based predictive tool cannot only present a decent overall accuracy, but also estimate the parametric trends relatively well. Over 95% of the data points can be predicted by the proposed correlations within a +/- 50% error band for both elongated bubbly flow and annular flow. Therefore, the flow-pattern based correlations can be applied for heat exchanger design to improve the understanding of the underlying heat transfer mechanisms and to guide the development of further enhancement techniques for flow boiling in micro/minichannels.