Investigation of flow patterns in a greenhouse with mechanically assisted ventilation

Abstract

In the present work, the effect of fan ventilation in an arc type tunnel greenhouse under the encumbering action of solar radiation is studied. Results are accrued for the air velocity, temperature, pressure, vapour and fresh air concentrations taking into account the plants' drag force and the buoyancy effects caused by higher temperatures prevailing at the upper part of the greenhouse. The numerical results are compared to experimental data, providing the appropriate base for the validation of the developed numerical model. Inside the greenhouse there is a tomato crop 1.5 m tall. For the simulation a 3D grid is created to figure the geometry of a real experiment, and the finite volume method is taken in hand to treat the fully elliptic partial differential equations' problem. Climatic data provided by the Centre of Research and Technology of Thessaly, Greece, were used in order to approach realistic conditions of experiment. Special items like the thermophysical and optical properties of covering material or the aerodynamic behaviour of the tomato crop are also considered. The results show the influence of the forced convection air flow patterns resulted from the mechanical assisted ventilation. Flow recirculations are presented due to buoyancy effects in areas where forced convection is limited via to the topology showing how the temperature gradients affect the flow. The conclusions of the comparison will feature a valuable guideline assisting in the improvement of a computational tool for the estimation and prediction for the optimum selection of mechanical installation for fan ventilation in various structural greenhouse specifications.