An experimental investigation was conducted to determine the effect of low-velocity air currents on water evaporation rates. The work was motivated by the large differences among the predictions of available correlations - which can be as much as a factor of four. A standard evaporation pan was enclosed in a room in which the ambient temperature and humidity as well as the water temperature in the pan were controlled. A wind tunnel was designed to provide a controlled, uniform air current above the pan up to a velocity of 1.45 m/s (285 fpm). At a constant ambient temperature of 20degC (68degF), the evaporation rates were measured for various air velocities, relative humidities, and water temperatures. The data were used to develop an empirical correlation for the evaporation rate per unit surface area as a function of the vapour pressure difference and air velocity. For a 95% confidence level, the error in the predicted evaporation rate was estimated to be less than + or - 16%.

KEYWORDS: year 1995, experiment, water, evaporation, air, speed, wind tunnels, ambient temperature, humidity, water temperature, climate chambers, relative humidity, vapour pressure, pressure difference, accuracy, measuring, air flow