An analytical study is performed for condensation heat transfer with quiescent or very slow vapor inside a horizontal elliptical tube under the simultaneous effects of the surface tension forces and gravity forces on the condensate film. Analytical solutions for both the local condensate film thickness and heat transfer coefficient have been expressed in terms of ellipticity e of the cross-section and the reverse Bond numbers. The dimensionless mean heat transfer coefficient-Nu for any ellipticity e and the reverse Bond number have also been obtained in this study. The results show that the effect of surface tension has an influence on the local heat transfer coefficient and hydrodynamics characteristics inside an elliptical tube; however, the effect upon the mean heat transfer coefficient is nearly insignificant. For the special case when e = 0 (circular tube), the reduced results coincide with classical Nusselt-type solutions. © 1994.
Chiou, J. S., Yang, S. A., & Chen, C. K. (1994). Laminar film condensation inside a horizontal elliptical tube. Applied Mathematical Modelling, 18(6), 340–346. https://doi.org/10.1016/0307-904X(94)90358-1