Research Paper: SEdStructures and Environment Wind driven ventilation of a mono-span greenhouse with a rose crop and continuous screened side vents and its effect on flow patterns and microclimate M. Teitel a, *, O. Liran a , J. Tanny b , M. Barak a a Institute of Agricultural Engineering, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel b Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel article info Article history: Received 12 December 2007 Received in revised form 7 May 2008 Accepted 19 May 2008 Available online 3 August 2008 Although high greenhouse tunnels are often used by growers in the Mediterranean basin, the data on the distributed microclimate within such structures is limited. Experiments were carried out in a naturally ventilated mono-span greenhouse with continuous screened side vents to determine the ventilation rate, temperature, humidity and air veloc- ity distributions and the energy partitioning of the incoming radiation. Results indicate that the ventilation rate increases linearly with wind speed. When the wind blows perpen- dicularly to the greenhouse opening plane there is a cross-flow between the windward and leeward openings that results in gradients in the air and crop temperatures between wind- ward and leeward sides. Gradients in temperature, humidity and air velocity are observed in the vertical direction as well. The temperature and humidity ratio were larger near the roof than near the crop while the air velocity was higher near the crop than near the roof. The gradients in the vertical direction were larger than those encountered in a horizontal plane in a direction parallel to the mean flow (from windward to leeward opening). The root mean square (RMS) values of the air velocity in all three components, the RMS of tem- perature normalised by the temperature difference between inside and outside and the turbulent fluxes were generally higher near the windward opening than near the leeward one. Nearly 75% of the net radiation in the greenhouse was consumed as latent heat by plant transpiration while only about 14% was converted to sensible heat. ª 2008 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction High tunnels are often used by growers in the Mediterranean basin. Such structures are cheaper than multi-span green- houses and are generally not equipped with sophisticated equipment for climate manipulation. They are usually naturally ventilated by side, roof or combined side and roof openings. Although nowadays they are widely used, only a few studies that consider the microclimate distribution in such enclosures have been made. The air exchange rate of a tunnel with continuous side openings was measured by Kittas et al. (1996) who used the tracer gas technique. In addi- tion, they measured air pressure difference between inside and outside at ground level simultaneously with outside wind speed, wind direction, and inside and outside air tem- peratures. Ventilation rates and pressure coefficients for * Corresponding author. E-mail address: grteitel@agri.gov.il (M. Teitel). 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.2008.05.012 biosystems engineering 101 (2008) 111–122