Enhanced CFD-based approach to calculate the evaporation rate in swimming pools

Abstract

An improvement of a formerly proposed CFD-based methodology (base model) for the estimation of water evaporation rate in swimming pools is presented here. This base model achieved satisfactorily on average (10% of relative error) under mixed and natural convection, but it deviated from the experimental measurements significantly (up to 45%) for conditions dominated by forced convection. The enhancement of the base model focusses on the adjustment of the air-water shear stress in terms of the average Reynolds number. First, a set of 32 laboratory-scale evaporation experiments under forced convection were carried out optimizing shear stress values toward getting a prescribed target for the evaporation rate estimation. In contrast to the base model, with this adjusted boundary condition the enhanced model gave rate values that fitted quite well (6%) with experimental measurements. Finally, a model validation was also developed by using two sets of experiments provided by the scientific literature. 145 cases were taken into account for which the enhanced model performed very satisfactorily and better on average than the base model (7% and 25% of average relative error, respectively). The improvement was even higher under forced convection prevailing conditions, with relative error of the order of the common experimental measurements.