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United States Department of Agriculture

Agricultural Research Service

Title: MODELING THE ENERGY BALANCE OF APPLES UNDER EVAPORATIVE COOLING

Author
item Evans, Robert

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2003
Publication Date: July 1, 2004
Repository URL: http://handle.nal.usda.gov/10113/9705
Citation: Evans, R.G., 2004. Modeling the Energy Balance of Apples Under Evaporative Cooling. Transactions of American Society of Agricultural Engineers. 47(4):1029-1037.

Interpretive Summary: Sunburn (or sun scald) of fruit surfaces exposed to direct sun is a major economic problem of fresh apples and other important horticultural crops. Evaporative cooling is one method to minimize sunburn damage. However, 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.

Technical Abstract: Sunburn (or sun scald) of fruit surfaces exposed to direct sun is a major economic problem of fresh apples and other important horticultural crops. Evaporative cooling is one method to minimize sunburn damage. However, 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.

Last Modified: 7/10/2014
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