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Energy balance of apples under evaporative cooling

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Sunburn (or sun scald) of fruit surfaces exposed to direct sun is a major economic problem of fresh apples and other important horticultural crops. There is a critical need to maximize evaporative efficiency and avoid excessive water use. A process-based energy balance model has been developed and compared with field data for apple skin temperatures during evaporative cooling to reduce sunburn on apples in the Pacific Northwest. The model worked well, although it tended to slightly overpredict during times with high advective heat energy. Automated control of evaporative cooling by cycling based on fruit core temperatures worked well in a controlled test stand and minimized total water use. Model results support the management of overtree evaporative cooling systems based on pulsing water applications at sufficiently high rates so that sufficient free water evaporating from the fruit surface will maintain core temperatures of exposed fruit in the 30°C to 32°C range. Results indicated that the model could potentially be used with sensor (e.g., thermocouples) feedback for the initiation, management, and control of overtree evaporative cooling systems to reduce sunburn and conserve water.
Evans, R.G.
Includes references
Transactions of the ASAE 2004 Jul-Aug, v. 47, no. 4
Journal Articles, USDA Authors, Peer-Reviewed
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