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A recent model for condensation in microchannels by the authors has been modified to investigate the effect of channel inclination. Provisional results are obtained for the case studied earlier for horizontal channels i.e. for R134a with saturated vapour at inlet and prescribed uniform wall temperature. Calculations give distributions around the channel perimeter of condensate film thickness and heat flux from which the mean (around the channel perimeter) heat flux and heat-transfer coefficient are found. Results are presented for square channels with side 0.5, 1.0 and 3.0 mm.

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The paper presents a theoretical model to predict film condensation heat transfer from a vapor flowing in a horizontal tube with equilateral triangular section minichannels or microchannels. The model is based on fundamental analysis which assumes laminar condensate flow on the channel walls and takes account of surface tension, vapor shear stress and gravity. The case considered here is where the channel wall temperature is uniform and the vapor is saturated at inlet. Sample numerical results are given for the channel size (side of triangle) of 1.0 mm and for refrigerant R134a. The general behaviour of the condensate flow pattern (spanwise and streamwise profiles of the condensate film), as well as streamwise variation in quality and local mean (over section perimeter) heat-transfer coefficient, are qualitatively in accord with expectations on physical grounds.