4291 -- Evaluation of the Correlations for Predicting Evaporative Loss from Water Body

Water evaporation is a natural phenomenon that is an important factor in system design and safety of systems in numerous engineering branches. There are a number of correlations obtained from experimental studies that predict the evaporative heat and mass loss from a water body. This study aims to summarize and to compare the existing evaporation correlations to determine the upper and lower bounding correlations for use in various thermal-hydraulic analyses of systems. Currently and widely used, six correlations found in the literature have been selected and tested using the major parameters of evaporation such as water temperature, air relative humidity, air velocity, and temperature. The comparison test cases show that ASHRAE (1991) and Ryan et al. (1974) equations result in the highest evaporative loss, while the Brady et al.(1969) equation provides the lowest evaporative loss in most conditions. Engineering designers may sometimes need the upper bound value of evaporative loss or sometimes the lower bound value for a conservative calculation. We conclude that using a single equation does not provide the conservative calculation for every situation and show which correlation gives the lower or upper bound for different conditions.

Units: Dual