多膜覆盖夜间气温变化模拟试验

Simulation Experiment of Air Temperature Variation in Multi-film Covering at Night

本试验针对多层塑料薄膜覆盖形成环境中夜间气温的变化进行分析,以期为完善多膜覆盖生产模式提供理论依据和数据支持。试验于2018年冬季在山东济南的4个拱棚内进行,拱棚内分别设置1层薄膜小拱棚、2层薄膜小拱棚、3层薄膜小拱棚以及未设置小拱棚,利用拱棚和小拱棚组成的1～4层薄膜覆盖模拟早春多膜覆盖下的温度环境,并进行测量分析。结果表明,内设小拱棚对拱棚内夜间气温的影响不大,拱棚内外气温高低存在不确定性;在本试验范围内,随着覆盖塑料薄膜层数的增多,多膜覆盖环境夜间的气温条件不断改善。表明,塑料薄膜提高温度的作用并不仅仅是由自身热工参数(热导率)引起的。MATLAB拟合分析结果表明,随着薄膜层数的增多,多膜覆盖夜间气温增幅逐渐变小,在本试验条件下覆膜层数以不超过5层为宜。

In order to provide theoretical basis and data supports for improving the production mode of covering, this experiment studied the nighttime air temperature formed by multi-films with tunnel shed and small tunnel shed as trial subjects. The experiment was carried out in 4 tunnel sheds with 0 or 2 small tunnel sheds covered by 0,1, 2 and 3 layers of films respectively in Jinan, Shandong Province in winter of 2018. The nighttime air temperature of tunnel sheds and small tunnel sheds formed by 1,2,3 and 4 layers of plastic film was measured and analyzed to simulate the temperature environment of early-spring season. The results showed that there were little differences among the nighttime air temperature inside tunnel shed which was installed 0~3-layer small tunnel shed inside, there were uncertainty in size between the air temperature inside and outside tunnel shed, and the nighttime temperature conditions were constantly improved with the number of plastic film layer increasing. The analysis indicated that the mechanism of raising the temperature surrounded by plastic film was not only due to its own thermal parameter(thermal conductivity). MATLAB fitting analysis results showed that the increment of nighttime temperature in multi-film covering became smaller with the number of film layers increasing. In this experiment, the number of layers in multi-film covering should not exceed 5 layers.