Natural Convection Driven Evaporation from a Water Surface

Abstract

We measure evaporation rates from water kept in an insulated tank and which is at a temperature higher than the ambient. Different schemes are used to obtain different temperature profiles in the water layer: a) water is heated from bellow, b) water left to cool after being heated, c) water heated from above with an IR heater, d) water heated from above in a very shallow tank. The idea of having these different schemes is to check the role of water side convection on evaporation rates. In cases a) and b) unstable stratification causes convection; in case c) we have stable stratification, and in case d), the temperature is uniform in the water layer. The heating-from-above experiments simulate some aspects of evaporation from natural bodies, like lakes, due to solar radiation. Evaporation rates were measured using a precision balance. Temperatures were measured in the water and in the ambient, and a thermal camera was used to monitor the water surface temperature and visualize the convection patterns. We present results of evaporation rates under the different conditions.