ISHS Acta Horticulturae 372: Symposium on Engineering as a Tool to reduce Pesticide Consumption and Operator Hazards in Horticulture
MEASUREMENT OF HEAT TRANSFER IN THERMAL WEED CONTROL |
| Author: | A. Bertram |
| Keywords: | Flame cultivation, working capazity, plant damage, forced convection |
| Abstract:
The knowledge about the heat transfer from the hot air to the plants is a necessary prerequisite for the optimization of thermal weeders. Consequently the fundamental thermodynamic principles of flame cultivation were worked out in a thermodynamic model. This has been used to calculate the heat transfer rates of different thermal weeders. To verify the thermodynamic model it was necessary to develop a measurement method to quantify the heat transfer rates of thermal weeders and to compare the results with the calculated values. The heat transfer rate is influenced by the thermal weeder and by the plant. As temperature and air velocity in a flame vary widely, a hot air tunnel was built to examine the heat transfer at defined and reproducible conditions of air velocity and temperature. The local heat transfer differences on a plant and the cooling influence of the transpiration lead to different temperatures on every measuring location even in the hot air tunnel. To overcome this problem, standardized metallic leaves have been developed. This metallic leaves have been brought into the hot air tunnel and the increase of the temperature has been compared to the expected values of the thermodynamic model. The aim of a thermal treatment is the plant. For the optimization of a thermal weeder, the demitrial effect on a plant by a thermal treatment had to be investigated. In a first step the heat transfer on a stem of basil (Ocimum basilicum) has been studied in the hot air tunnel. | |
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