Research Paper: SEdStructures and Environment Effect of wind direction on greenhouse ventilation rate, airflow patterns and temperature distributions M. Teitel a, *, G. Ziskind b , O. Liran a,b , V. Dubovsky b , R. Letan b a Agricultural Engineering Institute, Agricultural Research Organization, The Volcani Center, POB 6, Bet Dagan 50250, Israel b Ben-Gurion University of the Negev, Department of Mechanical Engineering, POB 653, Beer Sheva 84105, Israel article info Article history: Received 8 May 2007 Received in revised form 26 March 2008 Accepted 12 September 2008 Published online 23 October 2008 The effect of wind direction, relative to a multi-span naturally ventilated greenhouse, on the airflow patterns and air temperature distribution inside the house and at the openings is investigated in the present study, in a greenhouse with vertical roof openings. Experi- ments in a full-scale greenhouse, CFD (Computational Fluid Dynamics) full-scale simula- tions and wind tunnel tests on a small-scale model were carried out. The results showed a significant effect of the wind direction on the flow patterns both inside the house and at the roof openings. Furthermore, wind direction significantly affected the ventilation rate and the air and crop temperature distributions. A reasonable qualitative agreement was achieved between the experiments, numerical simulations and wind tunnel tests with respect to flow patterns through the openings. Quantitatively, the numerically predicted ventilation rates are in reasonable agreement with estimates of ventilation rates obtained by a model given in the literature. However, numerically predicted air velocities at the greenhouse openings differ from the measured values and possible reasons for the differences are highlighted and discussed. ª 2008 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction Ventilation is one of the most important factors in the design of greenhouses since it directly affects the average air temperature, humidity and CO 2 concentration within the enclosed space. However, as pointed out by Boulard et al. (2002), it is not sufficient to evaluate heat and mass transfer from the greenhouse to the surroundings based on the perfectly stirred tank approach, because recent concerns on crop quality and preservation of the environment require that climate heterogeneity, i.e. flow patterns and temperature and humidity distributions within the house, is also taken into account. In recent years a large amount of research on greenhouse ventilation was done using field experiments and, to some extent, CFD (Computational Fluid Dynamics) modelling. Field experiments use a range of techniques to measure ventilation rates, in a more or less direct way, with tracer gas techniques and energy balances being the most widely used (Teitel and Tanny, 1999) whereas CFD simulation is a powerful tool which makes it possible, in addition to estimating the overall ventilation rate, to characterize the entire flow field inside and outside the greenhouse. Despite the large amount of work done on estimating the effect of wind speed on ventilation, the characteristics of airflow through roof openings of a multi-span greenhouse are not sufficiently documented, especially with regard to two very important features, namely, the effects of wind direction and magnitude on the flow patterns at the planes of the openings of a multi-span greenhouse, and the detailed flow pattern at crop level. In particular, Boulard et al. (1996) experimentally * Corresponding author. E-mail addresses: grteitel@agri.gov.il (M. Teitel), gziskind@bgu.ac.il (G. Ziskind). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/issn/15375110 1537-5110/$ – see front matter ª 2008 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2008.09.004 biosystems engineering 101 (2008) 351–369