Numerical investigation on heat and mass transfer of slit finned tube heat exchanger with humid flue gas

Very few studies have been reported on the fundamental mechanism analysis the augmentation of heat and mass transfer for the convection and condensation processes in the slit finned tube heat exchanger under dehumidifying conditions. By developing a 3D numerical model for the condensation of the slit finned tube heat exchanger under dehumidifying conditions, the heat and mass transfer characteristics were investigated under different the geometrical and operational parameters. The models neglecting convective mass flux or neglecting the water vapor loss can greatly enlarge the deviations of numerical results with respect to experimental data. The synergy angles are smaller in the windward and leeward sides of slits where the velocity field has a better synergy with both temperature field and the mass field. The slits on the fin not only increase the disturbance of fluid but continuously destroy the developments of thermal and mass concentration boundary layers, greatly enhancing the heat and mass transfer. The latent heat transfer is significantly greater than the sensible heat transfer, which accounts for 71.7% of the total heat transfer rate when inlet velocity is 1 m center dot s(-1) and volume fraction of water vapor is 15%. The increases in the inlet velocity, and the volume fraction of water vapor can enhance the heat and mass transfer coefficient of wet flue gas. Whereas, the increase in inlet velocity can reduce the difference of synergy for the velocity field and the temperature or mass concentration gradient field of different fin tubes.