A numerical study of heat and mass transfers in a large water reservoir is presented. This water reservoir is being considered as a parallelepiped tank which vertical and lower walls are adiabatic and impermeable. The equations that govern the natural convection in water are solved using the finite volume method and Thomas algorithm. The adequacy between the speed and pressure fields is ensured by the SIMPLE algorithm. We analyze the influence of water depth, the density of the solar flux captured by the free water surface, the ambient conditions (temperature and rela relative humidity of the ambient air, wind speed) on the spatio-temporal spatio temporal distributions of temperature and the speed in the water reservoir as well as the evaporated water mass flow. This modeling is completed by a
simulation, using meteorological data from Burkina Burkina Faso and the concept of a standard day for the evaporation of this reservoir. The results obtained show that the evaporated water flow rate increases under a high solar flux rate and decreases in case of high relative humidity rate. The months of September ember and August have a lower evaporation rate according to the typical day used compared to the other months represented and the fluxes of the various heats have significant impacts on the evaporation rate.

Numerical Study Evaporation Meteorological Parameters Natural Convection