On the prediction of heat transfer in micro-scale flow boiling

Xu et al. have recently published a set of results for boiling heat transfer measurements in a multi- channel micro- scale evaporator for flow boiling of acetone in triangular cross- section channels ( hydraulic diameter of 155.4 mm). In the present collaboration, we assess our current capability to predict this independent flow boiling data set with a fluid not in the original database and also much smaller in size using the phenomenological three- zone model of Thome, Dupont, and Jacobi. The method models boiling in small diameter channels in the elongated bubble/ slug flow regime. The boiling data falling in this regime are identified here using a new micro- scale flow pattern map proposed by Revellin in order to utilize only test data corresponding to the elongated bubble flow mode. The decrease of the measured wall temperature due to the heat spread by longitudinal conduction through the heat sink was investigated through a finite differences analysis. In addition, a data reduction procedure different than that one used by Xu et al. was used and, consequently, some differences in the heat transfer behavior were found. Based on the present database, a new set of empirical parameters for the three- zone model was proposed. The conjugated effect of flow pattern and bubble/ slug frequency on the heat transfer coefficient was also investigated.