Co-Authors:
Teitel, M., Agricultural Engineering Institute, Agricultural Research Organization, Volcani Center, P.O.B. 6, Bet Dagan 50250, Israel
Liron, O., Agricultural Engineering Institute, Agricultural Research Organization, Volcani Center, P.O.B. 6, Bet Dagan 50250, Israel
Haim, Y., Agricultural Engineering Institute, Agricultural Research Organization, Volcani Center, P.O.B. 6, Bet Dagan 50250, Israel
Seginer, I., Civil and Environmental Engineering, Technion, Haifa, 32000, Israel
Abstract:
The use of screens to reduce insect entry into greenhouses has become a common practice in many countries. The screens act as a mechanical barrier that prevents migratory insects from reaching the plants, and thus reduce the incidence of direct crop damage and of insect-transmitted virus diseases. As a consequence, the need for pesticide application is reduced. However, the exclusion of very small insects requires installation of fine mesh screens across the greenhouse openings which impede ventilation and thus increase temperature and humidity within the greenhouse. To explore ways in which the resistance of screens to airflow can be reduced, experiments were done in a wind tunnel with screens of different porosity (0.62, 0.52 and 0.4) that were inclined to the flow and with a concertina-shape screen. The experimental results show that a screen that is inclined to the airflow can reduce the resistance in comparison to the case where the flow is normal to the screen. Inclined screens allowed in present experiments airflow higher by about 15-30% than a screen which the flow was normal to it. The experiments in the wind tunnel also show that a concertina-shape screen allows a higher airflow (by about 25%) in comparison to a flat screen under similar pressure drops across the screens. Velocity profiles downstream inclined and concertina-shape screens are reported.
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