Evaporation from heated water bodies: Predicting combined forced plus free convection

Abstract

Recent measurements at the National Geothermal Test Facility at East Mesa, California, and the Savannah River Plant, South Carolina, have spurred a renewed look at evaporation from heated water bodies. Theoretical analyses are provided for each of four evaporation regimes that could be experienced at heated ponds, ranging from free convective layers to forced convective layers. Differences among regimes are highlighted by calculations appropriate for the Savannah River site where water temperatures reach 70°C and underscore the difficulty in finding a single evaporation equation to adequately cover the entire range. Consequently, a new equation is developed which combines free and forced convection in a different manner from previous equations: evaporation is computed as the square root of the sum of the squares of the respective components. The new equation and several existing equations are compared with evaporation measured at water bodies at the Savannah River and the East Mesa sites.