MEASUREMENT AND NUMERICAL SIMULATION OF MICROCLIMATE IN A NATURALLY-VENTILATED LARGE MULTI-SPAN GLASSHOUSE

Within the practical context of mechanisms comprehension involved in greenhouse climate, this paper considers the problem of natural ventilation with particular attention paid to the determination of the ventilation rate. In view to gain some physical insight on to this process under temperate climate, both experimental and numerical approaches have been developed. Measurements were carried out in a 2500 m² commercial glasshouse equipped with continuous roof vents. Speed and direction of the wind and air temperature were measured outside the building. Temperature was also recorded both on the walls and in the middle of the greenhouse. The tracer gas (N₂O) technique was used to assess the ventilation rate. Numerical resolution was performed using a commercial Computational Fluid Dynamics (CFD) package. The model solves the 2D Navier-Stokes equations with a - closure. The boundary conditions were inferred from the experimental data. The simulated ventilation rate was compared to the experimental data, for three different openings configurations, and with other results already published in the literature. Results show that wind speed and direction combined with vent opening size strongly affect the inside air flow and temperature patterns as well as the ventilation rate. Simulated ventilation flux seems however to be underestimated probably because the model doesn’t consider leakage rates and 3D circulations. Such a tool could nevertheless be improved in order to be used as a design device to optimise ventilation in greenhouses.