J. Flores-Velazquez, J.I. Montero, E.J. Baeza, J.C. López, J.J. Pérez-Parra, S. Bonachela
Because high temperatures lower greenhouse crop yields, cooling is regarded as a primary need in plant production under cover. Due to their impact, ventilation systems are efficient for climate control. Although mechanical ventilation is more predictable than the natural one, its description is still complex and its simplification requires a deep understanding of the phenomenon. The objective of this study was to characterize the internal climate developed in a three-span, mechanically-ventilated greenhouse without crop. The greenhouse was located in Almeria (Southern Spain), under Mediterranean environmental conditions. In this study, the CFD technique was used to simulate the performance of mechanical ventilation in a three-span greenhouse plastic covered 22.5 m wide, 28 m long and 3 side walls and 4.7 m span height. Three mechanical fans and windows make up the ventilation system. Three configurations of the roof vents were tested: closed, 30% open, and completely open. Scalar fields for the air temperature, as well as ventilation rates and velocity fields were examined on the different vent configurations. For the three configurations, CFD simulations indicated that the ventilation rate increased slightly when the roof ventilators were open. The ventilation rates were relatively stable and non-dependent on external conditions. In all cases, simulations showed the existence of zones with slow velocity under the entrance window, and a good circulation in the crop zone along the greenhouse. Compared to the greenhouse with closed roof ventilators, some temperature reduction and better uniformity was observed for the greenhouses with open roofs. In any case, the combination of mechanical ventilation and natural ventilation through the roof openings had limited effect in the internal climate, due to the fact that mechanical ventilation was predominant over natural ventilation under the conditions considered in this study.
Flores-Velazquez, J., Montero, J.I., Baeza, E.J., López, J.C., Pérez-Parra, J.J. and Bonachela, S. (2011). ANALYSIS OF MECHANICAL VENTILATION IN A THREE-SPAN GREENHOUSE USING COMPUTATIONAL FLUID DYNAMICS (CFD). Acta Hortic. 893, 653-660
DOI: 10.17660/ActaHortic.2011.893.69
eolic effect, refrigeration, roof windows, thermal gradient, tracer gas

Acta Horticulturae