Evaporative cooling of a ventilated greenhouse rose crop
Evaporative cooling of a ventilated greenhouse rose crop
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DOI：
10.1016/j.agrformet.2006.05.002
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发表时间：
2006-08
影响因子：
6.2
通讯作者：
M. Fuchs;E. Dayan;E. Presnov
中科院分区：
文献类型：
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作者：
M. Fuchs;E. Dayan;E. Presnov
在温暖的天气里，温室作物可能会遭受过度的热负荷。通过作物蒸腾作用和湿垫和风扇系统的自由水分蒸发来评估潜热冷却的程序。该程序使用并发的外部气候因素作为输入数据。它将建筑特征（屋顶覆盖物的尺寸和辐射特性）、植物叶片（叶面积、气孔导度）和通风量作为参数来计算热传递系数。对温室玫瑰作物（Rosa indica L cv ' Mercedes Long '）的测量表明，能量平衡方程的数值解准确地预测了温室内作物的蒸腾作用、叶片温度、空气温度和湿度。通风率为每小时30次，外部空气湿度低于50%，水分充足的植物的蒸腾作用使温室内的叶子和空气温度低于外部温度，即使太阳辐射达到最大值。在进气口用蒸发湿垫冷却可以降低温室内的蒸汽压差，降低蒸腾速率。然而，加在垫层蒸发和作物蒸腾上的总潜热耗散高于不加湿垫层的作物蒸腾。通过蒸发垫的空气和作物的能量平衡的组合解准确地预测了玫瑰作物的蒸腾和内部温度和湿度。蒸发垫大大冷却了空气；但蒸腾叶温的降低幅度较小。当外界湿度增加时，衬垫的蒸发减少。湿垫运行时作物蒸腾速率几乎与外界湿度和通风量无关。
Greenhouse crops may suffer from excessive heat load in warm weather. A procedure is developed to evaluate latent heat cooling by means of crop transpiration and free water evaporation from a wet pad and fan system. The procedure uses concurrent external climatic factors as input data. It treats construction characteristics (dimensions and radiometric properties of the roof cover), plant foliage (leaf area, stomatal conductance) and ventilation rate as parameters to calculate heat transport coefficients. Measurements in a greenhouse rose crop (Rosa indica L cv ‘Mercedes Long’) show that the numerical solution of the energy balance equation predicts accurately crop transpiration, foliage temperature, air temperature and humidity inside the greenhouse. With ventilation rates of 30 volume changes per hour and external air humidity below 50%, transpiration of a plant well supplied with water, cools the foliage and the air in the greenhouse below external temperature even when solar radiation is at its maximum value. Cooling obtained with an evaporative wet pad at the air inlet lowers vapour pressure deficit in the greenhouse and decreases transpiration rate. Still, total latent heat dissipation added to pad evaporation and crop transpiration is higher than that obtained by crop transpiration without the wet pad. The combined solution of the energy balance of the air passing through the evaporative pad and of the crop predicts accurately transpiration of the rose crop and internal temperature and humidity. The evaporative pad cools the air considerably; but the lowering of transpiring leaf temperature is only minor. Evaporation from the pad decreases when external humidity increases. Crop transpiration rate when the wet pad operates is nearly independent of external humidity and ventilation rate.