High resolution local heat transfer and pressure drop infrared measurements of two-phase flow of R245fa within a compact plate heat exchanger

An experimental study is presented to characterize two-phase thermal and hydraulic performance of a prototype corrugated plate heat exchanger with small pressing depth. In particular, upward flow boiling of low pressure refrigerant R245fa was investigated for a prototype fabricated with two plates of only 1 mm pressing depth with a chevron angle of 65. High spatial and temporal resolution infrared measurements were obtained by self-calibration of the IR camera to measure local (pixel-by-pixel) heat transfer coefficients during diabatic tests and local frictional pressure drops over the entire plate during adiabatic tests. Two-phase experiments were carried out for mass fluxes from 10 to 85 kg m(-2) S-1, heat fluxes from 225 to 4100 W m(-2), saturation temperatures from 19 to 35 degrees C and vapor qualities from 0.05 to 0.90. The two-phase frictional pressure drops increased with mass flux and vapor quality while they decreased with increasing saturation temperature. A new correlation for predicting the local frictional pressure gradient through the test section was proposed. The present model captured the entire frictional pressure drop database within a bandwidth of 30%, providing a mean absolute error of 10% and mean error of 0.2%. The local flow boiling heat transfer coefficients were found to increase with mass flux, heat flux and saturation temperature while rising, leveling off and then decreasing with increasing vapor quality. (C) 2016 Elsevier Ltd. All rights reserved.