ISHS Acta Horticulturae 710: International Symposium on Greenhouses, Environmental Controls and In-house Mechanization for Crop Production in the Tropics and Sub-Tropics
ACOUSTICAL MEASUREMENT FOR VERTICAL TEMPERATURE PROFILES IN ALLEY BETWEEN ROWS OF TOMATO PLANTS |
| Authors: | K. Mizutani, R. Futamata, K. Kudo, Y. Hirayama, L. Okushima |
| Keywords: | mean temperature, vertical temperature distribution, sound probe, TOF, thermocouple |
| DOI: | 10.17660/ActaHortic.2006.710.20 |
| Abstract:
Sound velocity is dependent on medium temperature and is estimated from time of flight (TOF) of the sound. We propose an acoustical method for vertical temperature profiles. The measurement object is a long and narrow space in an alley between rows of tomato plants. A sound probe, which consisted of a loud speaker, a long propagation path and a microphone, measured the spatial mean temperature without contact. Our present thermometry system, which had four sound probes perpendicularly arranged in line, measured vertical temperature profiles, and realized high-speed temperature measurement further than the thermocouples with a time delay which was caused by the thermal capacity. The vertical temperature profiles with four layers were monitored for 22 minutes by four sound probes in a large-scale greenhouse of tomato plants. The sound probes were installed at heights of 0.565, 0.865, 1.165 and 1.465 m. The four propagation lengths of each sound probe were all equal to 20.000 m. Four thermocouples per layer were installed along the propagation path. In this experiment, 44 thermocouples were used as reference. Experimental results of the vertical temperature profiles measured by four sound probes were in agreement with the profiles measured with the 16 thermocouples. In addition, the time response of the sound probe was about two minutes faster than that of the thermocouple. It was confirmed that the temperature was higher in the lower region of the vertical temperature distribution, because of the effect of heat pipes along the ground. | |
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