This paper investigates the ability of two widely used evaporation models: Dalton based correlations and similarity theory results by comparing with experimental measurements. A series of experimental investigations are carried out over a wide range of water temperatures and air velocities for 0.01 B Gr/Re 2 B 100 in a rectangular heated pool. The results show that for forced convection regime satisfactory results can be achieved by using the modified Dalton correlations, while, due to ripples appear on the water free surface, similarity theory under predicts the evaporation rate. In the free convection regime, Dalton based correlations even with modification are not able to predict acceptable results. For mixed convection regime, although both the similarity theory and Dalton based correlations without modification are not able to predict the mild non-linearity behavior between water evaporation rate and vapor pressure difference, but they obtain relatively satisfactory results. A dimensionless correlation using the experimental data of all convection regimes is proposed to cover different water surface geometries and air flow conditions. List of symbolsD H 2 o;Air Binary mass diffusion coefficient m 2 /s D h Hydraulic diameter of rectangular duct (m) g Gravitational acceleration m/s 2 g m;H 2 o Mass transfer coefficient Gr Mass transfer Grashof number H Height of rectangular duct (m) h fg Enthalpy of vaporization (J/kg) k Thermal conductivity w/mk L Length of water pan (m) _ m e Evaporation rate of water kg/m 2 h m f H 2 o

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In the present study, the applicability of widely used evaporation models (Dalton approach-based correlations) is experimentally investigated for natural, forced, and combined convection regimes. A series of experimental measurements are carried out over a wide range of water temperatures and air velocities for 0:01 Gr=Re 2 100 in a heated rectangular pool. The investigations show that the evaporation rate strongly depends on the convection regime's Gr/Re 2 value. The results show that the evaporation rate increases with the difference in vapour pressures over both forced convection (0:01 Gr=Re 2 0:1) and turbulent mixed convection regimes (0:15 Gr=Re 2 25). However, the escalation rate of evaporation decreases with Gr/Re 2 in the forced convection regime whereas in the turbulent mixed convection it increases. In addition, over the range of the free convection regime (Gr=Re 2 ! 25), the evaporation rate is affected not only by the vapour pressure difference but also by the density variation. A dimensionless correlation using the experimental data of all convection regimes (0:01 Gr=Re 2 100) is proposed to cover different water surface geometries and airflow conditions.

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