ISHS Acta Horticulturae 51: Symposium on Protected Cultivation of Flowers and Vegetables
NATURAL CONVECTION HEAT TRANSFER IN COVERED PLANT CANOPIES |
| Authors: | M. Iqbal, J.A. Stoffers |
| Abstract:
A facility has been designed and constructed to carry out the study of free convection from leaves in a covered plant canopy. The system considered is one with long parallel rows of canopies with finite widths, heights and spacings between them. To generate free convective air flow patterns inside the canopies, leaves have been simulated by small electric bulbs. These 'bulb canopies' were constructed in such a way so as to provide variable (leaf surface area)/(volume) ratios. The electrical system was designed to provide various levels of energy input at different heights of the canopies which would correspond to desired solar flux absorption at these heights. Convective heat transfer coefficients (in terms of Nusselt numbers) are presented for a leaf area density of approximately 90 cm2 / 1000 cm3. Heat transfer coefficients were measured on two types of thin plate 8 cm x 8 cm size, one having both surfaces of copper and the other having both surfaces covered with white paper. The first such plate simulated a leaf with uniform surface temperature and the second a leaf with uniform surface heat flux. These plates were fixed in a vertical position at about the centre of the canopy. From the experimental data, two heat transfer correlations have been presented for the two plates. The results show that the difference between the values obtained from the two simulated leaves is not greater than about 15 percent. | |
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