Effectiveness of horizontal air flow fans supporting natural ventilation in a Mediterranean multi-span greenhouse

Scientia Agricola

Alejandro López¹  Diego Luis Valera¹  Francisco Domingo Molina-aiz¹  Araceli Peña¹ 

[1] ,Universidad de Almería Centro de Investigación en Biotecnología Agroalimentaria BITAL Almería,Spain

关键词: climate control;    microlimate;    sonic anemometry;   

DOI  :  10.1590/S0103-90162013000400001

来源: SciELO

【 摘 要 】

Natural ventilation is the most important method of climate control in Mediterranean greenhouses. In this study, the microclimate and air flow inside a Mediterranean greenhouse were evaluated by means of sonic anemometry. Experiments were carried out in conditions of moderate wind (≈ 4.0 m s-1), and at low wind speed (≈ 1.8 m s-1) the natural ventilation of the greenhouse was supplemented by two horizontal air flow fans. The greenhouse is equipped with a single roof vent opening to the windward side and two side vents, the windward one being blocked by another greenhouse close to it, while the leeward one is free of obstacles. When no fans are used, air enters through the roof vent and exits through both side vents, thus flowing contrary to the thermal effect which causes hot air to rise and impairing the natural ventilation of the greenhouse. Using fans inside the greenhouse helps the air to circulate and mix, giving rise to a more homogeneous inside temperature and increasing the average value of normalized air velocity by 365 %. These fans also increase the average values of kinetic turbulence energy inside the greenhouse by 550 % compared to conditions of natural ventilation. As the fans are placed 4 m away from the side vents, their effect on the entrance of outside air is insufficient and they do not help to reduce the inside temperature on hot days with little wind. It is therefore recommended to place the fans closer to the side vents to allow an additional increase of the air exchange rate of greenhouses.

【 授权许可】

CC BY   
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