CFD based determination of temperature and humidity at leaf surface

A numerical model based on the energy balance has been developed for computing with the Fluent CFD code temperature and humidity at leaf surface for low light levels. Crop transpiration and aerial flows were coupled and a single parameter model for the stomatal response of leaves to radiation flux has been considered. Validation of the results at leaf level has required an experimental setup based on Münger cells to quantify temperature, relative humidity and the different heat fluxes for single bean leaves. Experiments have been performed for three alternate low light/dark periods. It was shown that the agreement between numerical and experimental results increases with the airflow intensity: the results are in good agreement for air relative humidity and the absolute error is lesser than 10% while it can reach 1 °C for air temperature due to the weak experimental temperature difference between inlet and outlet flows. The terms of the heat balance on the leaf surface have also been compared and variable agreements have been found, relative error varying from 10 to 40%. The numerical results highlight their dependence on the minimal stomatal resistance value, numerical and experimental results agreement increasing with minimal stomatal resistance varying from 66 to 200 s m−1. These results underline the importance of the values of the parameters included in the model used for CFD simulations of heat and mass transfer on single leaf surface and by extension to transfers with whole crops and particularly protected crops.