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ISHS Acta Horticulturae 148: III International Symposium on Energy in Protected Cultivation

WIND TUNNEL TESTING ON AIRFLOW AND TEMPERATURE DISTRIBUTION OF A NATURALLY VENTILATED GREENHOUSE

Authors:   S. Sase, T. Takakura, M. Nara
DOI:   10.17660/ActaHortic.1984.148.42
Abstract:
Measurements have been made of airflow and temperature in a naturally ventilated single-span greenhouse installed in a wind tunnel. A logarithmic mean velocity profile was generated in the wind tunnel and Archimedes number was taken into account to ensure the similarity of ventilation phenomena.

The results indicate that the airflow caused by wind effect is influenced primarily by the configuration of ventilator through which air comes in; the hinged ventilator leads to the main flow following the internal surfaces of the roof, while the sliding-door type side ventilator allows the main stream of air to travel along the floor. Under still conditions, it is shown that the airflow pattern due to stack effect is independent of the configuration of ventilators and the degree of temperature rise in the crop space depends relatively on the opening area in side walls. For the case of combined action of wind and stack effects, it is illustrated that the pattern of temperature distribution is largely determined by the airflow patterns. This changes considerably with increasing wind velocity below 1–2 m· s-1 due to the interaction of wind and stack effects resulting in the average temperature rise to be relatively constant. The airflow pattern is independent of higher wind velocity due to wind effect acting dominantly. Additionally, the 3-dimensional distribution of temperature is discussed with reference to changing wind direction.

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