Condensation of steam mixed with non-condensable gas on vertical heat exchanger tubes in circumstances with free convection

Abstract

Condensation heat transfer is significantly influenced by the geometrical and thermal-hydraulic parameters of the heat exchanger. Therefore, in order to assess their effects, experiments were conducted focused on the steam condensation on the outer surface of a vertical tube in the presence of a non-condensable gas. The experimental data on the heat transfer coefficient (HTC) were produced using three different tubes, with outer diameters of 21.5 mm, 33.6 mm, and 42.4 mm. The pressure, air mass fraction, and wall subcooling in the experiments ranged from 200−600 kPa, 0.05−0.80, and 16.1−55.6 K, respectively. Based on the data set consisting of the experimental data from the present study and the data collected in previous studies, an empirical correlation was developed, which accounts for the effects of the geometrical and thermal-hydraulic parameters. The applicable ranges of the proposed correlation for the air mass fraction, Jakob number, diffusion Reynolds number, and aspect ratio are 0.049−0.890, 8.83 × 10−3−3.41 × 10−2, 1.61−2.37 × 102, and 2.65−17.0, respectively. The maximum error of the correlation was calculated to be 20% with a 95% confidence level, when compared against the experimental data.