Development of a new correlation for pre-dry out evaporative heat transfer coefficient of R290 in a microchannel

Abstract

Although many correlations have and are being developed for two-phase heat transfer coefficient correlation in microchannels, none has the desired accuracy yet. This paper presents prospective improvements in the convective heat transfer coefficient correlation accuracy for the dry-out conditions; when the heat transfer coefficient drops at a certain vapor quality. An accurate heat transfer coefficient forecast is needed to minimize over or under design, conserve energy and material, and maximize the performance. R290 has been reported to be more energy efficient than R22. A new correlation relevant for R290 across 831 sets of experimental data points in a microchannel was generated by optimizing six variables in the nucleate boiling suppression factor, S, and force convective factor, F, of a selected superposition type correlation. The new correlation was optimized for saturation temperature ranging between 5 and 25 °C, diameter ranging between 1.0 and 6.0 mm, heat flux ranging between 2.5 and 60 kW/m2, and mass flux ranging between 50 and 500 kg/m2s. The MAE was reduced from 21.84 to 17.02% for pre-dry out data. The new correlation may be utilized to estimate the heat transfer coefficient of R290 in heat transfer analysis in a microchannel under the investigated operating conditions. The optimization approach utilized here has the potential of continuously improving the MAE of any heat transfer correlation for any refrigerants considered.