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Spatial distribution of air temperature and relative humidity in the greenhouse as affected by external shading in arid climates

文献类型： 外文期刊

作者： Ahmed, Hesham A. 1 ; Tong Yu-xin 1 ; Yang Qi-chang 1 ; Al-Faraj, Abdulellah A. 3 ; Abdel-Ghany, Ahmed M. 3 ;

作者机构： 1.Chinese Acad Agr Sci, Inst Environm & Sustainable Dev Agr, Beijing 100081, Peoples R China

2.Key Lab Energy Conservat & Waste Management Agr S, Beijing 100081, Peoples R China

3.King Saud Univ, Coll Food & Agr Sci, Dept Agr Engn, Riyadh 11451, Saudi Arabia

4.Sanaa Univ, Fac Agr, Dept Agr Engn, Sanaa 2124, Yemen

关键词： greenhouse; temperature; humidity; distribution; uniformity; evaporative cooling; shading; arid climate

期刊名称：JOURNAL OF INTEGRATIVE AGRICULTURE （ 影响因子：2.848； 五年影响因子：2.979 ）

ISSN： 2095-3119

年卷期： 2019 年 18 卷 12 期

页码：

收录情况： SCI

摘要： The effect of external roof shading on the spatial distribution of air temperature and relative humidity in a greenhouse (T-in and RHin) was evaluated under the arid climatic conditions of Riyadh City, Saudi Arabia. Two identical, evaporatively-cooled, single-span greenhouses were used in the experiment. One greenhouse was externally shaded (G(s)) using a movable black plastic net (30% transmissivity), and the other greenhouse was kept without shading (G(c)). Strawberry plants were cultivated in both greenhouses. The results showed that the spatial distribution of the T-in and RHin was significantly affected by the outside solar radiation and evaporative cooling operation. The regression analysis showed that when the outside solar radiation intensity increased from 200 to 800 W m(-2), the T-in increased by 4.5 degrees C in the G(c) and 2 degrees C in the G(s), while the RHin decreased by 15% in the G(c) and 5% in the G(s), respectively. Compared with those in the G(c), more uniformity in the spatial distribution of the T-in and RHin was observed in the G(s). The difference between the maximum and minimum T-in of 6.4 degrees C and the RHin of 10% was lower in the G(s) than those in the G(c) during the early morning. Around 2 degrees C difference in the T-in was shown between the area closed to the exhausted fans and the area closed to the cooling pad with the external shading. In an evaporatively-cooled greenhouse in arid regions, the variation of the T-in and RHin in the vertical direction and along the sidewalls was much higher than that in the horizontal direction. The average variation of the T-in and RHin in the vertical direction was 5.2 degrees C and 10% in the G(c) and 5.5 degrees C and 13% in the G(s), respectively. The external shading improved the spatial distribution of the T-in and RHin and improved the cooling efficiency of the evaporative cooling system by 12%, since the transmitted solar radiation and accumulated thermal energy in the greenhouse were significantly reduced.

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