955 Dynamics of Climatic Conditions in a Greenhouse: Two Locations in Mexico F. Rojano Department of Agricultural and Biosystems Engineering The University of Arizona Tucson, Arizona USA J. Flores-Velázquez and F. Villarreal-Guerrero Facultad de Agronomía y Veterinaria Universidad Autónoma de San Luis Potosí San Luis Potosí S.L.P. Mexico A. Rojano Postgrado en Ingeniería Agrícola y Uso Integral del Agua Universidad de Chapingo Km. 38.5 Ctra. Mex-Tex. 56230 Texcoco, Edo de Mexico Keywords: natural ventilation, Computational Fluid Dynamics, greenhouse climate, microclimate modeling Abstract For most greenhouse locations in Mexico, climate dynamics are primarily influenced by the local weather because they mainly have naturally ventilated structures. Since during the year there is weather fluctuation, greenhouse climate demands strategic use of ventilation having effects on other climate variables. This work conducts an investigation about a representative greenhouse, which is simulated by Computational Fluid Dynamics (CFD) in order to know the effects of weather conditions from two locations in Mexico on the air temperature and humidity within the greenhouse. A typical greenhouse of northeast of Mexico, with a natural ventila- tion system was studied. This greenhouse has three spans and an orientation North- South. The model considers tomato crop effects by adding the evapotranspiration phenomenon. Then, the goal is to compare with experimental data three represen- tative scenarios that cover the wind speed variation and its associated climatic variables such as temperature, humidity and solar radiation. Furthermore, it is possible to combine the effects of the climatic variables with thermal properties of the cover, buoyancy effects, physical properties of the insect-proof screen and the estimation of evapotranspiration. Additionally, this investigation serves to initially provide accurate estimations of energy dynamics and the most convenient location within the greenhouse to log climatic data. INTRODUCTION Greenhouses in Mexico represent a growing industry that is taking advantage of climate conditions, low cost of operations and a demanding domestic and international market of fresh produce. In the last ten years, greenhouses have been introduced in most of the countryside with improved results regarding the quality and quantity of produce. Location was defined due to nearness of the market, of an available infrastructure and some others at places where weather can diminish operation of equipment for climate control. This investigation is focused in the weather effects from two representative climatic conditions of Mexico: Texcoco and San Luis Potosi, where climate is not demanding intensive use of climate control equipment. Since wind speed is the main variable to regulate temperature inside of the greenhouse, merging data of two locations (Texcoco and San Luis Potosi) find out three representative scenarios, associating climatic variables such as temperature, humidity and solar radiation from the experimental data set for the greenhouse located in San Luis Potosi and taken for the simulations using CFD. Previous works have demonstrated that CFD applied to greenhouses can illustrate the interaction of different heat and mass transfer phenomena such as conduction, convection, radiation and evaporation (Kacira et al., 2004; Fatnassi et al., 2006; Norton et al., 2007; Bournet et al., 2010; Sapounas et al., 2010; Pierre and Boulard, 2010; Kichah et al., 2012; Rico-Garcia et al., 2012; Bartzanas et al., 2012). Furthermore, special inter- action between the crop and the environment can be represented through user-defined Proc. IS on New Technol. for Env. Control, Energy-Saving and Crop Prod. in Greenhouse and Plant Factory – GreenSys 2013 Eds.: Jung Eek Son et al. Acta Hort. 1037, ISHS 2014