Evaporative mass transfer in turbulent forced convection duct flows

Experiments were performed to determine the mass transfer characteristics for evaporation from partially filled pans of distilled water recessed in the floor of a flat rectangular duct through which turbulent air flow was passed. During the course of the experiments, parametric variations were made of the Reynolds number of the air flow, the streamwise length of the pan, and the distance between the top of the pan and the water surface (hereafter referred to as the step height). For all of the operating conditions of the experiments, the measured Sherwood numbers were well correlated with the Reynolds number provided that the step height was used as the characteristic dimension. Guided by analytical considerations, a second correlation was constructed which provides Sherwood number predictions for operating conditions corresponding to pans longer than those used in the present experiments. By making use of the analogy between heat and mass transfer, it was shown how Nusselt numbers can be obtained from the Sherwood number correlations.