Steam condensation on tube-bundle in presence of non-condensable gas under free convection

In the presence of non-condensable gases, the effects of thermal-hydraulic parameters on steam condensation on a tube-bundle heat exchanger differ from those for a single-tube because the geometry of the tube-bundle enhances shadow and suction effects. In this study, experiments were performed to investigate these effects on three types of tube-bundle heat exchangers with pitch-to-diameter ratios of 2.0, 2.5, and 3.0, and pressures, air mass fractions, and wall subcooling of 20 0-50 0 kPa, 0.2-0.7, and 20-55 K, respectively. The local bundle factor was defined as the difference in condensation heat transfer coefficients between a single-tube and tubes in a tube-bundle. Therefore, a local bundle factor correlation, which accounts for the shadow and suction effects, was developed. The applicable ranges of the local bundle factor correlation for local pressure loss, Bird's suction factor, and blockage fraction were 0.267-0.734, 1.12-1.98, and 0.044-0.304, respectively. An average bundle factor was derived from the local bundle factor. The developed correlation applying the average bundle factor predicted the heat transfer coefficients for the obtained experimental data within an error of 8.50 %. (c) 2021 Elsevier Ltd. All rights reserved.