冷风挡帘对日光温室内气温影响的数值模拟及其结构优化

Numerical simulation and verification for the effect of keep-off shade on temperature field in solar greenhouse

研究冷风挡帘结构对寒冷干旱地区日光温室内温度分布的影响。以内蒙古呼和浩特近郊农户生产中使用的日光温室为研究对象,分别对具有冷风挡帘的日光温室(试验温室)和无挡帘的普通温室(对照温室)内的气温进行连续测试,建立2种日光温室在自然通风时的计算流体力学模型。结果表明:在距地面0.1m高度(作物冠层),试验温室在0.6~7.0m范围内的气温显著高于对照温室(α=0.05),温差最大值为4.2℃,最小值为1℃。将近地表气温低于20℃的区域面积值作为评价指标,当通风口底端竖直高度为0.25 m、宽0.3 m,太阳辐射≥300 W/m2,室外风速≤1.2m/s时,冷风挡帘最优结构参数为迎风长度0.84m,倾斜角度76°,此时不同进口风速能满足大部分耕作区域地表气温在12:00时高于20℃的生产要求。

To explore the effect of keep-off shade on temperature field in solar greenhouse in cold-arid areas, greenhouses used universally for agricultural production in a suburb of Hohhot, Inner Mongolia are study objects. The internal temperature in greenhouses with keep-off shade （experimental group） and greenhouses without keep-off shade （control group） were investigated continuously. Numerical models based on CFD method of these two types of greenhouses in natural ventilation were built. The results showed that temperatures in experimental greenhouse at 0.1 m height （accordant to crop canopy） are higher than the control group among whole span areas, the maximum of temperature difference was 4.2 ℃ ,while the minimum was 1 ℃. Area scale of land surface temperature under 20 ℃ was regarded as evaluation index,when the vent is 0.3 m wide and the bottom is 0.25 m high,solar radiation is more than 300 W/m2, wind speed is less than 1.2 m/s,our results demonstrate that the best windward length is 0.84 m and the best oblique angle is 76° in order to ensure the land surface temperature of most arable zones are higher than 20 ℃ under the condition of natural ventilation.