An Experimental Evaluation of Thermal Stratification in a Fan-Ventilated Greenhouse

摘要

Experiments were performed to investigate air velocity and vertical air temperature distributions in a fan-ventilated greenhouse. The effects of ventilation rate and canopy size on the allocation of airflow between canopy and non-canopy areas were examined. The data suggested that the ratio of the air velocity within the canopy to the mean velocity of the entire greenhouse cross-section depended on not only the area ratio of canopy to greenhouse cross-section, but also ventilation rate. The ratio of canopy air velocity to greenhouse average velocity decreased if ventilation rate increased. The effects of outside solar radiation, ventilation rate, evaporative cooling pads, and presence of a canopy on the vertical air temperature variations were also investigated. The vertical air temperature variation increased approximately linearly with solar radiation. Use of an evaporative pad increased the temperature variation. Increasing ventilation rate resulted in reduced air temperature variation. The presence of a canopy modified the vertical temperature distribution and reduced temperature variations as well.