CFD analysis of the climate inside a closed greenhouse at night including condensation and crop transpiration

International audienceHumidity control is a key factor in greenhouse management as it impacts the growth and quality of most greenhouse crops. Low temperature accompanied with high humidity levels for instance may lead to condensation which in turn may create favourable conditions for fungal diseases like botrytis. CFD (Computational Fluid Dynamics) is today widely used to predict the climate inside greenhouses. But up until now, the condensation phenomenon has been hardly addressed in CFD studies. The aim of this work is to analyse the heat and mass transfers occurring inside a closed mono-span glasshouse compartment using CFD simulations and focusing on night-time cases. A 2D transient model which solves the classical RANS equations in combination with the k-ε closure for turbulence was considered. Radiative exchanges between the sky and the components of the greenhouse were considered through a specific submodel. User defined functions were implemented to take account of both condensation along the roof and crop transpiration. The validation of the model was undertaken on the basis of experiments conducted in a 100 m2 Venlo-greenhouse with Impatiens pot plants grown on shelves. Results showed the ability of the model to predict air and leaf temperatures inside the greenhouse as well as air humidity levels. Then, the influence of factors such as the external conditions, heating and glass properties on the greenhouse climate and especially on the condensation process was investigated through a sensitivity analysis. For each case, the heat gain and loss along the inside and outside greenhouse roof were analysed and compared. The results of the simulations clearly show the influence of these factors on the greenhouse air temperature and condensation flux