Optimization of Vent Configuration during Ventilation for Dehumidification Purpose Using Computational Fluid Dynamics

摘要

High humidity usually occurs in the prolonged and closed greenhouse during the winter. In eastern China, natural ventilation is widely adopted for greenhouse dehumidification despite of the fact that it may cause certain heat loss problems. For making a good compromise between dehumidification effectiveness and heat loss prevention, the optimization of vent configuration for multi-span greenhouses was attempted in the present study by Computational Fluid Dynamics (CFD). A CFD model was developed based on the solution of the Navier-Stokes equations with the Boussinesq assumption and a k-ε closure. In this model, the insect-proof screen was considered as a porous medium and the crop was neglected due to the small plant size for simplicity. The model was first successfully validated with experimental data obtained from a 1980 m~2 11-span plastic greenhouse divided into two compartments separated by a plastic partition. The validated model was then used to investigate the influences of the airflow pattern, the humidity distribution and the corresponding heat loss in the ventilated greenhouse under different vent configurations (i.e. side, roof and side plus roof) through unsteady analysis. Simulations show that roof ventilation tends to be the best for the purpose of thermal insulation and dehumidification effect under winter climate conditions.