冷冻空间软硬吸合面间湿空气呼吸效应机制

When the refrigerating room temperature fluctuates around the set values, magnetic seals will periodically inhale high-humidity hot air and exhale low-humidity cold air. The breathing effect results in the increase of energy consumption and the decrease of preservation quality. To reduce these adverse effects, the amount of air infiltration must be precisely controlled. Therefore, the breathing effect mechanism of the magnetic seals should be investigated and the quantitative description of the breathing effect should be achieved. As the infiltration path, infiltration potential and infiltration mechanism are key factors of the breathing effect, they will be investigated, sequentially. Firstly, a penetration path model which is capable of characterizing the 3-D morphology of micro-rough crack under mechanical stress will be established, based on the combination of stress analysis and 3-D numerical characterization; secondly, a coupled model for the fields of temperature, pressure, humidity in refrigerating room under the periodical influence of moisture air condensation will be developed for the quantitative description of the coupled infiltration potential; finally, a micro analysis of the moisture air migration in the crack of magnetic seal under single infiltration potential will be done, and the prediction models for moist air infiltration under the influence of synthetic and the antithetic pressure potential, temperature potential and humidity potential will be established. The research results will provide theoretical basis for optimizing magnetic seals of refrigerating room, and enrich the theory of moisture air infiltration in cracks.

冷冻空间温度在设定的温度上下限内波动时，门封吸合面将周期性地吸入外界高湿度热空气和呼出内部低湿度冷空气，这种“呼吸效应”导致能耗上升及被保存物品的品质损害；其不利影响的减弱有赖于对空气渗透量的精确控制，这就需要掌握冷冻空间软硬吸合面呼吸效应的机理并实现定量描述。本项目针对影响湿空气呼吸效应的渗透路径、渗透推动势、渗透机制等关键因素开展研究；首先通过应力分析、粗糙表面形貌的数字化表征，建立反映应力作用下吸合面缝隙三维微观形貌的渗透路径模型；然后建立软硬吸合面结构对于周期性水汽冷凝影响下的冷冻空间内湿度场与温度场、压力场耦合模型，实现软硬吸合面耦合渗透推动势量化描述；最后在对单一渗透推动势下软硬吸合面缝隙空气迁移微观分析的基础上，建立湿度、温度、压力三个渗透推动势同向和反向耦合作用下空气渗透量模型。项目成果为冷冻空间软硬吸合门封的优化设计提供必需的基础模型，并丰富缝隙间湿空气渗透理论。

冷柜、冰箱等设备维持在低温环境下运行，需要消耗大量电能产生持续冷量来抵消热湿负荷，其中湿空气渗透带来的热湿负荷占据着主要部分。为降低冷冻空间能耗，最直接的措施就是减小湿空气渗透。湿空气渗透主要受到湿度、压力、温度渗透势以及渗透路径的影响；为了减少湿空气渗透，实现降低冷冻空间能耗的目标，需要明确冷冻空间软硬吸合面湿空气渗透特性。本文设计并搭建了冷冻空间软硬吸合面湿空气渗透速率测试实验台，测试了冷冻空间软硬吸合面湿空气渗透特性的变化规律，通过表面形貌观测和理论研究分析了软硬吸合面渗透流动类型，建立了湿空气中水蒸气和空气渗透速率预测模型。主要研究内容及结果如下：.1）提出了基于空气泄漏测试流量法和水蒸气渗透干法测试原理的冷冻空间门封软硬吸合面湿空气渗透测试方法，搭建了湿空气渗透速率测试实验台，可实现不同压力、温度、湿度渗透势下的湿空气渗透速率测试；.2）通过仪器观测得到了软硬吸合面表面形貌，结合材料弹性变形理论计算得到接触应力影响下表面形变结果，揭示了冷冻空间门封吸合面处的气体流动；.3）通过水蒸气渗透速率测试实验，研究了水分渗透速率随水分分压差的变化规律，结果表明，在只有湿度渗透势作用时，冷冻空间门封吸合面处的水蒸气渗透速率随压差增大而增大，两者变化规律呈线性。根据软硬吸合面水分渗透的理论分析和实验数据，建立了渗透速率预测模型；模型预测值与实验值的最大误差小于15%；.4）空气渗透速率测试的实验研究结果表明，在温度和压力耦合渗透势下，冷冻空间门封吸合面处的空气渗透速率随温度升高而增大；冷冻空间门封吸合面处的空气渗透速率随压差增大而增大，且增大的速率越来越快，两者关系非线性。通过多孔介质渗流理论并结合实验数据拟合渗透特性系数，建立了空气渗透速率预测模型；模型预测值与实验测试值的最大误差小于8%。.研究结果为冷冻空间门封优化设计提供必需的基础模型，并丰富间隙湿空气渗透理论。