日光温室主动蓄热循环系统结构优化与能量传递的机制研究

The wall of active solar greenhouse has better thermal storage performance compared with that of traditional solar greenhouse. However, active solar greenhouse is characterized with main limits: (1) the air duct has lower heat transfer efficiency; (2) the thermal storage body has less heat storage; (3) the indoor air flow and temperature distribution is not uniform (the temperature on the north side is higher, the temperature on the south side is lower), which affects the crop yield and quality. Our previous study found that the wind channel, heat storage materials, airflow velocity and path had important influence on the heat storage of active solar greenhouse. Therefore, based on the structural characteristics of heat storage cycle system in active solar greenhouse, we want to optimize the structural design and investigate the mechanism of energy transfer. We will first test the heat transfer ability of different air ducts and heat storage materials, and construct heat transfer models. We will then identify the influence of different airflow velocities and paths on the heat transfer characteristics of active heat storage wall, and improve the heat transfer model. Finally, we will reconstruct the active heat storage cycle system based on the north wall and soil, studying the energy transfer mechanism of north wall-soil-air-crop, and further optimizing the system, which was verified by the environment and crop growth status. After this project, the heat storage performance of active solar greenhouse can be improved, as well as the indoor thermal environment and air distribution. This study will theoretical knowledge for the structure optimization of active solar greenhouse heat storage cycle system.

虽然主动蓄热日光温室墙体与传统被动蓄热墙体相比具有较好的蓄热效果，但是风道传热效率较低、蓄热体蓄热量较小，且室内气流及温度分布不均匀（室内靠北侧温度较高、南侧温度较低），影响作物产量与品质。申请人前期研究发现，风道及蓄热材料、气流运动速度及路径对主动蓄热日光温室的蓄热效果具有重要影响。因此，本项目根据日光温室主动蓄热循环系统的结构特点，开展优化设计与能量传递的机制研究。首先，测试不同传热风道及蓄热材料的传热量，构建其传热模型；其次，测试不同气流运动速度及路径对主动蓄热墙体传热特性的影响，完善并扩展主动蓄热墙体的传热模型；最后，重构基于后墙-土壤联合蓄热的主动蓄热循环系统，研究后墙-土壤-空气-作物的能量传递机制，进一步优化该系统，通过环境及作物生长状况进行验证。通过本项目的实施，可以提高主动蓄热日光温室的蓄热性能、改善室内热环境与气流分布，为日光温室主动蓄热循环系统的结构优化提供理论依据。

现有主动蓄热日光温室墙体具有较好的蓄热效果，对改善室内夜间热环境起到了重要作用，但也存在前屋面热量损失大、建造成本高、蓄热量较小、传热效率较低、气流运动方式不合理之处，未将后墙及土壤的蓄热潜能充分发掘。亟需开展主动蓄热循环系统墙体与土壤的结构优化和传热特性的研究。为此，结合课题组前期研究成果，本文首先从前屋面保温入手，优化保温措施，降低热量损失；其次从墙体与结构入手，应用新材料、新形式改善墙体蓄热与保温；最后从主动蓄热气流运动入手，优化运动路径，提升主动蓄热效能。围绕日光温室立体循环主动蓄热系统结构优化与传热特性展开研究，主要研究结果如下：（1）在同等天气条件下，混凝土管沙柱后墙(W3)和轻骨料加气混凝土砌块后墙(W2)对于温室内温度的保持均优于传统普通粘土砖墙(W1)。（2）改变管道形式能够改善地中热交换系统的换热量，且改善程度与土壤质地无关；在管道上设置大量孔洞，对换热的改善效果最为显著。（3）顶进底出分布风道(DF)是3种主动蓄热风道布置中最优的，室内平均温度提升最明显，夜间温度最高，温度更为均匀。