Wind tunnel measurements and numerical simulations of water evaporation in forced convection airflow

摘要

The aim of this work is to investigate the relationship between evaporation from heated water surfaces and mean aero thermal properties of a forced airflow. Flows with Reynolds numbers varying between 2475 and 49,503 were considered. Both wind tunnel measurements and numerical simulations were used. The experimental results were obtained in an installation consisting of a low speed wind tunnel and an evaporation tank. The numerical study was performed through a 3D-CFD code. To validate the numerical formulation the predicted results were compared with the experimental measurements for the mass transfer at the free surface of the water tank and with correlations available in the literature. A good agreement was achieved which indicates an interesting capacity of the CFD program to predict the phenomena engaged. The dependence of the rate of evaporation with air velocity, water-air temperature difference and relative humidity is also addressed. The results obtained with both methodologies clearly show that the rate of evaporation is mainly dependent of the airflow velocity. The water-air temperature difference and the relative humidity also have an important effect, but much less than the airflow velocity. For small airflow velocities the rate of water evaporation is also small and presents only a slightly dependence from the temperature difference and the relative humidity.