Numerical simulation of solar radiation, air flow and temperature distribution in a naturally ventilated tunnel greenhouse

摘要

Catherine Baxevanou1, Dimitrios Fidaros1, Thomas Bartzanas1, Constantinos Kittas1,2(1. Center for Research and Technology-Thessaly, Institute of Technology and Management of Agricultural Ecosystems, Technology Park of Thessaly, 1st Industrial Area, 38500 Volos;2. University of Thessaly, Department of Agriculture, Crop Production and Agricultural Environment, Fytokou St., N. Ionia, GR-38446, Magnesia, Greece)?Abstract: The effect of solar radiation distribution in a typical agricultural building was numerically investigated, taking into account the thickness of the cover, its spectral optical and thermal properties. A two dimensional mesh was used to render the building's geometry, and the Discrete Ordinate (DO) model for simulating the radiation, taking into accounts its spectral distribution in three wavelength bands. Based on the meteorological data of October for the region of Volos (Greece), two parametric studies were carried out, dealing with the variation of intensity and angle of the incoming solar radiation and with the optical properties differentiation of covering materials. The flow recirculation, due to the buoyancy effect, showed the importance of internal temperature gradients, although forced convection which resulted from natural ventilation was dominant. It was concluded that cover material with high absorptivity deteriorate the natural ventilation increasing the air temperature by convection, and favoring the development of secondary recirculation where the air is trapped. Furthermore, high absorptivity reduces the available Photosynthetically Active Radiation (PAR) but it distributes it equally inside the greenhouse. Finally, the ability of the material to transmit the solar irradiance in the wavelengths corresponding to PAR with comparable absorptivity improved as the refractive index decreased.