Falling-film evaporation over horizontal rectangular tubes: Part I-Experimental results

An experimental study on falling-film evaporation on horizontal rectangular tubes, the external geometry of extruded flat, microchannel tubes, was conducted. Previous falling-film evaporation studies have focused on horizontal and vertical round tubes, and the usage of microchannel tubes provides a promising new heat exchanger design option. The test sections used in this study have external dimensions of 203 x 1.42 x 27.4 mm (length x width x height) and were tested with water as the refrigerant. Heat transfer coefficients were measured for saturation temperatures from 10 to 30 degrees C, test section spacings from 5 to 15 mm, heat fluxes from 10 to 20 kW m(-2), and film Reynolds numbers of 48 to 544. This paper, Part I, reports the experimental methodology and the results, while in the companion paper, Part II, models for predicting heat transfer are presented. (C) 2020 Elsevier Ltd and IIR. All rights reserved.