Cooling Fan-ventilated Greenhouses: a Modelling Study |
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| Institution: | 1. Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan;2. The Chugoku Electric Power Co., Inc., 4-33 Komachi, Naka-ku, Hiroshima 730-8701, Japan;1. AREVA Solar, Mountain View, CA, United States;2. Purdue University, West Lafayette, IN, United States;3. University of California, Merced, CA, United States;1. Faculty of Natural Resources and Earth Sciences, University of Kashan, Kashan, Iran;2. Institute of Energy Infrastructure (IEI), Department of Civil Engineering, College of Engineering, Universiti Tenaga Nasional (UNITEN), 43000, Selangor, Malaysia;3. Department of Biological and Agricultural Engineering, Zachry Department of Civil & Environmental Engineering, Texas A&M University, College Station, TX, USA;4. Department of Water Engineering, Semnan University, Semnan, Iran;5. Department of Civil Engineering, Faculty of Engineering, University of Malaya (UM), 50603, Kuala Lumpur, Malaysia;6. National Water and Energy Center, United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates;7. Water, Energy and Environmental Engineering Research Unit, University of Oulu, Finland;1. Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University, PO Box 2460, Riyadh 11451, Saudi Arabia;2. Department of Engineering Sciences, Community College, Umm Al Qura University, PO Box 715, Makkah 21955, Saudi Arabia;3. Department of Plant Production, College of Food and Agriculture Sciences, King Saud University, PO Box 2460, Riyadh 11451, Saudi Arabia;1. Department of Architecture, Built Environment, and Construction Engineering (DABC), Politecnico di Milano, Via Ponzio 31, 20133, Milano, Italy;2. Department of Energy, Politecnico di Milano, Via Lambruschini 4, 20156, Milano, Italy;1. Department of Informatics, ceiA3, CIESOL, Ctra. Sacramento s/n, University of Almería, Almería, Spain;2. Beijing Research Center for Information Technology in Agriculture, National Engineering Research Center for Information Technology in Agriculture, National Engineering Laboratory for Agri-product Quality Traceability, Meteorological Service Center for Urban Agriculture, China;3. Meteorological Administration - Ministry of Agriculture and Rural Affairs, Key Laboratory of Agri-informatics, Ministry of Agriculture, Beijing, China |
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| Abstract: | A model for fan-ventilated greenhouse cooling is presented in which the primary heat transfer surfaces (cover/structure, canopy and floor) are represented as three parallel planes. Validation of the model was accomplished using data collected over 14 days. Agreement was good, with canopy temperatures over-predicted by only 0·1%, air temperatures in the canopy under-predicted by 0·5%, humidity of the canopy air under-predicted by 1·6% and transpiration rates under-predicted by 1·4%. Simulation runs suggest that when evaporative pad cooling is not used, little advantage is derived from increasing airflow rates beyond about 0·05 m3 m?2 s?1. When evaporative pad cooling is used, however, both air and canopy temperatures decline with increasing airflow rates up to 0·13 m3 m?2 s?1, the highest level considered. Increasing canopy size is predicted to be more influential in reducing air temperatures when evaporative pad cooling is used than when it is not, but its effect on canopy temperature is expected to be approximately the same whether or not evaporative pad cooling is used. With no evaporative pad cooling, the evapotranspiration coefficient (i.e., the ratio of energy used for transpiration to incoming solar energy) is predicted to range from 1·75 for an outside temperature of 36·8°C and an outside humidity ratios of 3·3 g kg?1 to 0·8 for an outside humidity ratio of 29·9 g kg?1 at the same temperature. With evaporative pad cooling, the coefficient is predicted to range from 0·6 to 0·8 at the same outside temperature and the same range of outside humidity ratios. |
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