基于土壤-空气蓄/放热特性的日光温室环境调控机理及设计原理研究

The greenhouse coupled with earth-air heat exchanger (EAHE) system helps to provide proper thermal and humidity environment for the greenhouse, and improves crop yields. However, airflow in each pipe of the multi-pipe EAHE structures is not equal, which results in the increase of pressure losses and the deterioration of heat transfer. The thermal and humidity environment in the greenhouse would be heavily affected. ..This project aims at investigating the mechanism of energy storage/release between air and earth, as well as the design method of EAHE both experimentally and numerically. The thermal contact resistance of the fluid-solid coupling surface was precisely analyzed, which was used to establish the fluid-solid coupling model of EAHE, and the evaluation index of uniformity was proposed. Then, the performance of energy storage /release between air and earth would be obtained. Taking the heat and humidity caused by the plants as the input boundary, the transient evaluation of the temperature and humidity distributions in the greenhouse was dynamically caught. The effect of energy storage/release performance between air and earth on the air distribution, and the thermal and humidity environment of the greenhouse was investigated. Based on the factor sensitivity analysis, the quantitative relations of the parameters were established. A design approach of the structure and flow character was proposed to gain stable thermal and humidity environment in the greenhouse. It provides methodological support in the engineering operation to improve the air distribution, thermal and humidity environment of the greenhouse.

土壤-空气换热器应用于日光温室可提供适宜的热湿环境，提高农作物产量，然而并联换热器气流分配不均造成流阻增加、传热衰减，严重影响日光温室热湿环境。. 本项目立足日光温室并联土壤-空气换热器的蓄/放热机理及设计方法研究。建立土壤-空气换热器-日光温室的全局流固耦合模型并辅以实验研究，精确解析流固耦合面的接触热阻，揭示气流分配特性对土壤-空气换热器压降和传热特性的影响规律，提出均匀性评价指标，获得土壤-空气蓄/放热特性；并以植物蒸腾产生的动态热湿载荷为边界输入，动态捕捉气流进入日光温室的热湿环境演变规律，查清土壤-空气蓄/放热特性对温室内气流组织及热湿环境的影响机理；借助影响因素敏感性分析，建立各参数的定量量化关系，构建土壤-空气换热器结构形式及出流特性的有效设计方法，实现日光温室环境精准调控。完善日光温室环境调控理论，并为土壤-空气换热器在日光温室的工程应用提供技术支撑。

日光温室是我国菜篮子工程的重要实现途径，保障蔬菜的全年供给。其热湿环境是影响植物生长的关键，而我国当前针对日光温室的环境调控，主要形式还是依赖于经验性的自然通风和保温。土壤-空气换热器可充分利用地热能，对昼夜、变季节下的日光温室的热湿环境进行调控，保障农作物生长环境，进而提高产量。然而并联换热器存在气流分配不均问题，造成流阻增加、传热衰减，影响日光温室热湿环境调控，实际效果大幅衰减。基于此，本项目建立了基于土壤-空气换热器-日光温室的理论模型，并搭建了实验台，理论和实验研究了土壤-空气换热器的出流特性及对日光温室热湿环境的影响，揭示了气流分配不均匀对多路并联土壤-空气换热器的换热作用机理，提出了日光温室土壤-空气换热器结构形式及出流特性设计方法，大幅提高了土壤-空气换机器对日光温室热湿环境的调控效果。具体获得的主要研究内容与成果如下：（1）通过建立土壤与换热器之间的流固耦合模型，对比分析了U型、Z型、L型等不同类型和结构的换热器内流量分配特性、压降特性，深入分析了土壤空气换热器进出流发展充分程度对气流均匀性的作用机制，揭示了不同类型及结构特征的换热器气流分配特性对土壤-空气换热器传热特性的影响规律，提出了均匀性评价指标，获得土壤-空气蓄/放热特性。（2）搭建了结合土壤-空气换热器的日光温室实验台，测量和总结了日光温室的热湿环境变化特性，并指导建立了结合土壤-空气换热器的日光温室理论模型，研究明确了土壤空气换热器及内循环、外循环、混风段结构等对温室内气流组织及热环境升温降温特性的影响关系。（3）基于以上研究，识别了土壤-空气换热器的敏感性影响因素，基于综合性能最优目标，定量研究了土壤-空气换热器结构参数、运行参数及其耦合关系，并进行了多参数结构优化，提出参数最优组合方式，获得了日光温室土壤-空气换热器结构形式及出流特性的定量设计方法，为日光温室环境调控提供理论基础。