Heat and mass transfer analogy applied to condensation in the presence of noncondensable gases inside inclined tubes

A theoretical and experimental investigation on steam condensation in presence of noncondensable gases within horizontal and inclined tubes is summarized in the present paper. A simple correlation mainly based on dimensionless numbers was derived and compared with previous formulations based on the diffusion layer model. The noncondensable gases presence during condensation is an important issue affecting the whole thermodynamic efficiency of the process, and for this reason highly investigated by many researchers. The experimental data obtained for condensation, inside horizontal or inclined tube (15°, 30° and 45°) with an internal diameter of 22 mm, of an air/steam mixture, at low mixture Reynolds numbers (< 6000), have been used to verify the present Heat and Mass Transfer Analogy (HMTA) formulation. In order to perform the heat and mass transfer analogy, the suction effect at the interface has been taken into account since it considerably affects temperature and concentration profiles and hence the transfer coefficients. The model of Chato is used for the condensate boundary layer since it has been identified to be the better model under the experimental condition. Finally, the experimental data have been compared with the theoretical Couette flow model with transpiration showing a quite good agreement.