Kim, K., Yoon, J., Kwon, H., Han, J., Son, J. E., Nam, S., Giacomelli, G. A., & Lee, I. (2008). 3-D CFD analysis of relative humidity distribution in greenhouse with a fog cooling system and refrigerative dehumidifiers. Biosystems Engineering, 100(2), 245-255.
Abstract:
The distribution of humidity in a greenhouse was studied using three-dimensional (3-D) computational fluid dynamics (CFD). The calculations were validated using experimental data from a single-span greenhouse without plants. Two types of humidity distribution were considered: humidifying using a fog cooling system, and dehumidifying using refrigerative dehumidifiers in addition to a fog cooling system. The simulation errors of RH were 0.1-18.4% with a fog cooling system and 1.1-13.1% with a fog cooling system and refrigerative dehumidifiers at each observation point. Contour maps were obtained from the 3-D CFD simulations to locate any non-uniformity in humidity distribution. The use of refrigerative dehumidifiers reduced the overall difference of humidity between the middle and bottom zones of a greenhouse, but the local distribution of humidity was uneven, especially close to the dehumidifiers. This study suggests that the developed 3-D CFD model can be a useful tool in designing and evaluating greenhouses with various configurations. © 2008 IAgrE.
Giacomelli, G. A. (2008). Procedding of International Workshop on Greenhouse Ebviromental Control and Crop Production in Semi-Arid Regions: Foreword. Acta Horticulturae, 797, 5-.
Tignor, M. E., Giacomelli, G. A., Kubota, C., Fitz, E., Wilson, S. B., Irani, T. A., Rhoades, E., & McMahon, M. J. (2006). Development of a web-based multi-media resource for environmental control modeling and greenhouse education. Acta Horticulturae, 719, 303-310.
Abstract:
A publicly accessible multimedia instrument for greenhouse education was developed for global use. The instrument consists of (1) greenhouse videos produced on site in Arizona. Vermont. Ohio and Florida that emphasize state-specific production, environmental control, labor, and marketing issues; (2) an interactive Flash-based greenhouse environment simulator that allows users to model greenhouse environments based on climate data from each of the four video locations; (3) a searchable digital repository containing hundreds of useful greenhouse images, videos, and lectures, and (4) a web-based method for instructors to evaluate perceived student learning of greenhouse concepts. The Interactive Greenhouse Environment Simulator is driven bv a mathematical model developed bv engineers which is linked to a Flash-based graphical user interface (GUI). Following user selection of climate, structure and environmental control choices, dynamic environmental information is shown graphically during the simulation, allowing users to model changes in the greenhouse environment.
Romero, P., Giacomelli, G. A., Choi, C. Y., & Lopez-Cruz, I. (2006). Ventilation rates for a naturally-ventilated greenhouse in Central Mexico. Acta Horticulturae, 719, 65-72.
Abstract:
The design and operation of greenhouse structures suitable for specific climate conditions is critical, especially when greenhouse cooling is expected to depend entirely on natural ventilation. The ultimate goal of this study was to investigate the potential enhancement of overall ventilation rates by optimizing greenhouse design parameters such as the area of inlet and outlet vents as well as the type of the insect screen utilized and its area. The Computational Fluid Dynamics (CFD) approach was used, verified by experimental data. Numerical simulations showed that the area of the ventilation openings has a significant effect on the air exchange rate, which increased about 25% when the vent area was enlarged from 6 to 15% of the greenhouse ground area. Another potential design change, the removal of the insect screen from the roof vents, increased the ventilation rates by 25% as compared to the current design. Enlarging the area of the insect screen on the side walls showed no significant improvement in ventilation.
Villarreal-Guerrero, F., Kacira, M., Fitz-Rodríguez, E., Linker, R., Kubota, C., Giacomelli, G. A., & Arbel, A. (2012). Simulated performance of a greenhouse cooling control strategy with natural ventilation and fog cooling. Biosystems Engineering, 111(2), 217-228.
Abstract:
In addition to ventilation, daily cooling must be provided for greenhouses located in semiarid climates to maintain the desired climate conditions for year-round crop production. High-pressure fogging systems have been successfully developed for greenhouse cooling. However the lack of control strategies, in combination with ventilation systems, especially passive ventilation, has limited their capabilities. A new cooling control strategy, which considered the contribution of humidification and cooling from the crop, was evaluated by computer simulations. The strategy controlled the amount of fog introduced into the greenhouse, as well as the percentage of vent openings to maintain desired values of greenhouse atmospheric vapour pressure deficit (VPD) and enthalpy, respectively, which would consequently affect air temperature. The performance was compared to constant fogging rate strategy, which was based on VPD. On average, the new strategy saved 36% water and consumed 30% less electric energy. Smaller air temperature and relative humidity fluctuations, and more consistent control, were achieved by varying the fog system operating pressure to provide a more optimum amount of fog for evaporative cooling. It was demonstrated by simulations that dynamically varying the fog rate and properly selecting the number of nozzles, savings of water and electric energy were increased, while still maintaining acceptable VPD and temperature. The improvements in the greenhouse climate achieved by the new strategy were due to its ability to dynamically manipulate fog rates, as well as, the vent configurations. © 2011.
