An improved heat transfer model for steam-air mixture condensation with the curvature effect on vertical tubes

Abstract

The condensation heat transfer on the external surface of a vertical slender tube in the steam-air mixture environment was investigated. The condensation heat transfer was analyzed using various open experimental datasets. A new model for the steam condensation with noncondensable gases applicable to the tubular configuration was developed. The proposed model is based on the analogy between heat and mass transfer; in particular, the correlation incorporates the effects of tube curvature under turbulent free convection conditions together with the wavy film effect. In addition, the film-vapor interfacial temperature was used to calculate the heat transfer coefficient and various physical properties, through an iterative technique instead of the wall temperature, which is commonly used in experimental correlations for convenience. Thereafter, the effects of three correction factors were individually investigated. The wavy film effect considerably changed the condensation heat transfer, about 20% on average. The curvature effect was also found to make a meaningful effect according to the convection conditions. And, the adoption of interfacial temperature was found to make a maximum 7% adjustment, but it would make a more significant effect in high heat transfer conditions. Overall, the proposed model predicted the experimental datasets reasonably well, i.e., within ±30% accuracy.