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首页> 美国卫生研究院文献>Sensors (Basel Switzerland) >Wind Tunnel Analysis of the Airflow through Insect-Proof Screens and Comparison of Their Effect When Installed in a Mediterranean Greenhouse
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Wind Tunnel Analysis of the Airflow through Insect-Proof Screens and Comparison of Their Effect When Installed in a Mediterranean Greenhouse

机译：通过防虫网的气流的风洞分析及其安装在地中海温室中的效果比较

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摘要

The present work studies the effect of three insect-proof screens with different geometrical and aerodynamic characteristics on the air velocity and temperature inside a Mediterranean multi-span greenhouse with three roof vents and without crops, divided into two independent sectors. First, the insect-proof screens were characterised geometrically by analysing digital images and testing in a low velocity wind tunnel. The wind tunnel tests gave screen discharge coefficient values of Cd,φ of 0.207 for screen 1 (10 × 20 threads·cm−2; porosity φ = 35.0%), 0.151 for screen 2 (13 × 30 threads·cm−2; φ = 26.3%) and 0.325 for screen 3 (10 × 20 threads·cm−2; porosity φ = 36.0%), at an air velocity of 0.25 m·s−1. Secondly, when screens were installed in the greenhouse, we observed a statistical proportionality between the discharge coefficient at the openings and the air velocity ui measured in the centre of the greenhouse, ui = 0.856 Cd + 0.062 (R2 = 0.68 and p-value = 0.012). The inside-outside temperature difference ΔTio diminishes when the inside velocity increases following the statistically significant relationship ΔTio = (−135.85 + 57.88/ui)0.5 (R2 = 0.85 and p-value = 0.0011). Different thread diameters and tension affects the screen thickness, and means that similar porosities may well be associated with very different aerodynamic characteristics. Screens must be characterised by a theoretical function Cd,φ = [(2eμ/Kpρ)·(1/us) + (2eY/Kp0.5)]−0.5 that relates the discharge coefficient of the screen Cd,φ with the air velocity us. This relationship depends on the three parameters that define the aerodynamic behaviour of porous medium: permeability Kp, inertial factor Y and screen thickness e (and on air temperature that determine its density ρ and viscosity μ). However, for a determined temperature of air, the pressure drop-velocity relationship can be characterised only with two parameters: ΔP = aus2 + bus.
机译：本工作研究了具有不同几何和空气动力学特性的三个防虫网对具有三个屋顶通风口且没有农作物的地中海多跨温室内空气速度和温度的影响，该温室分为两个独立的部分。首先，通过分析数字图像并在低速风洞中进行测试，对防虫屏风进行几何表征。风洞测试得出，筛网1的筛网排放系数Cd，φ为0.207（10×20螺纹·cm -2 ；孔隙度φ= 35.0％），筛网2为0.151（13×30）屏幕3的螺纹·cm -2 ;φ= 26.3％）和0.325（10×20螺纹·cm -2 ;孔隙率φ= 36.0％）速度为0.25 m·s -1 。其次，当在温室中安装滤网时，我们观察到开口处的排放系数与在温室中心测得的空气流速ui之间的统计比例，ui = 0.856 Cd + 0.062（R 2 = 0.68，p值= 0.012）。当内部速度按照统计学上显着的关系ΔTio=（−135.85 + 57.88 / ui） 0.5 （R 2 = 0.85和p时，统计学上显着的关系增加时，内外温度差ΔTio减小-value = 0.0011）。不同的螺纹直径和张力会影响滤网的厚度，这意味着相似的孔隙率很可能与非常不同的空气动力学特性相关。屏幕必须以理论函数Cd，φ= [（2eμ/Kpρ）·（1 / us）+（2 eY / Kp 0.5 ）] 为特征-0.5 将屏幕 Cd，φ的排放系数与风速 us 相关。这种关系取决于定义多孔介质空气动力学行为的三个参数：渗透率 Kp ，惯性因子 Y 和筛网厚度 e （以及空气温度确定其密度ρ和粘度μ）。但是，对于确定的空气温度，压降-速度关系只能用两个参数来表征：Δ P = aus 2 + 公共汽车。

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