基于CFD的不同通风方式塑料大棚降温效果研究

Cooling Effect of Plastic Greenhouse with Different Ventilation Modes Based on CFD

为确定合理的塑料大棚通风口配置及通风形式,提高大棚夏季降温效果,采用试验和CFD模拟相结合的方法,对两种通风口配置(两侧底部、两侧底部+顶部)和两种通风口形状(水平卷膜、垂直卷膜)大棚内的夏季6—7月温度和气流场特征进行了研究。模型经过实测验证,气温模拟值与实测值变化趋势基本吻合,均方根误差1.27℃、平均相对误差分别为3.7%。结果表明:与仅有两侧底部通风相比,两侧底部和顶部通风配置明显提高降温效果,番茄冠层高度昼均温、升温速率分别降低0.4~2.1℃和0.4℃/h,通风率增加50%,温度、气流分布均匀度提高;与顶部水平卷膜通风相比,垂直卷膜通风大棚内冠层昼均温、升温速率分别降低0.2~1.2℃和0.2℃/h,通风率提高20%,但温度、气流的空间分布均匀性稍差。综合比较,同时采用两侧底部加顶部垂直卷膜通风的大棚通风降温效果明显。

Based on the reasonable configuration and ventilation form of plastic greenhouse, so as to achieve effective cooling in summer, by way of actual observation and CFD model, the typical temperature field and air flow field of side opening greenhouse, roof plus side opening greenhouse, horizontal roll-up greenhouse and of vertical roll-up greenhouse during June and July were studied. The model was verified by actual measurement, and the simulated values were basically consistent with the measured value, with root mean square error(RMSE) of 1.27℃ and mean relative error(MRE) of 3.7%, respectively. According to the study, compared with side openings alone, roof plus side openings improved the cooling effect significantly, decreased the daily average temperature and heating rate of tomato canopy height by 0.4~2.1℃ and 0.4℃/h, respectively, increased the ventilation rate by 50%, and enhanced the temperature and air distribution uniformity. Compared with top horizontal roll-up shape, vertical roll-up shape improved the cooling effect significantly, decreased the daily average temperature and heating rate of tomato canopy height by 0.2~1.2℃ and 0.2℃/h, respectively, increased the ventilation rate by 20%, but slightly reduced the temperature and air distribution uniformity. Comprehensive comparison showed that the plastic greenhouse with side opening and top vertical film rolling ventilation worked well in ventilation and cooling.