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Condensation heat transfer coefficients in mini-channels were measured with smaller measurement uncertainties than previously obtained using three specially designed copper test sections. Single-phase experiments validated the approach. Data are reported for R134a in 1 mm square, triangular, and semi-circular multiple parallel minichannels cooled on three sides. A parametric study was conducted over a range of conditions for mass flux, average quality, saturation pressure, and heat flux. Mass flux and quality were determined to have significant effects on the condensation process, even at lower mass fluxes, while saturation pressure, heat flux, and channel shape had no significant effects. The lack of shape effects were attributed to the three-sided cooling boundary conditions. Because there was no significant surface tension enhancement, the macro-scale Shah (2009) correlation best predicted the data, with a mean average error (MAE) of 20 to 30% for all geometries.

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