日光温室根区热环境相变调控系统设计与性能试验

为探索一种节能高效的日光温室热环境调控模式,以鞍II型日光温室为原型制作试验温室模型并设计了相配套的日光温室根区热环境相变调控系统,包括相变集热单元、潜热储存与交换单元、根温调节单元、循环泵组和循环管路5部分,并制定出系统热性能测试方案。通过对比试验,研究系统在单路循环模式下运行对日光温室模型室内空气、栽培基质不同深度温度的调节效果,以及对温室模型中紫叶生菜幼苗生长指标的影响。结果表明,冬季运行条件下,系统可以有效蓄积太阳辐射热,实现日光温室的高效能量收集和热环境调控,减少室内空气温度波动,提高基质根区温度。典型晴天天气测试时,试验温室20 cm深度处基质平均温度均高于对照温室。此外,与对照温室相比较,试验温室中生菜幼苗的株高、茎粗、单株叶面积、最大叶宽可分别提高13.4%、11.9%、79.1%、35.3%,表明试验温室内热环境更利于紫叶生菜幼苗的生长。

Application Effect of Greenhouse Root Zone Thermal Environment Control System with Latent Functionally Thermal Fluid

In order to explore an energy-efficient thermal environment control model in greenhouse, the application of thermal environment phase change control system was studied in solar greenhouse. A solar greenhouse root zone thermal environment control system was designed and built, including the phase change thermal unit, latent heat storage and exchange unit, root temperature control unit, circulation pump group and circulation pipeline. The latent functionally thermal fluid was used as liquid heat transferring medium in the heat collection, delivery and release of solar radiation. The system included three different work modes, and the thermal performance testing project was formulated. In winter of 2014, the operation performance of the designed system and application effect on lettuce seedlings were tested through controlled experiment of three different operation conditions, using two greenhouse models with the same construction and root zone thermal environment control system. The results indicated that the designed system significantly reduced the indoor air and shallow substrate temperature fluctuations in experimental greenhouse model, and significantly lowered the everyday highest indoor temperature and obviously increased root zone temperature of root zone substrates in winter, thus improving balance of temperature distribution among substrate layers with different depths. During the whole winner test process, the everyday highest indoor air temperature and the average fluctuation range of air temperature were averagely decreased by 7.2% and 5.1%, respectively, and the average 20cm depth root zone temperature and the average fluctuation range were increased by 15.1% and 39.0%, respectively. Among the three operation stages, system performances of the stage with flow rate of 3~4L/min was the optimum one, with the most obvious increases of average temperature and average fluctuation range of 20cm deep substrate, as well as the most significant rise in reduction percentages of temperature differences between 5cm deep and 20cm deep substrates. In addition, the plant height, stem diameter, leaf area per plant and width of maximum leaf of lettuce seedlings in the model were increased by 13.4%, 11.9%, 79.1% and 35.3%, respectively. Overall, the effect of the system was remarkable in sunny days. In conclusion, the phase change heat collecting system can effectively control the air the root zone thermal environment in greenhouse and promote seedling growth of vegetables.