【作者】 王海东；

【导师】 刘俊杰；

【作者基本信息】 天津大学 ， 供热、供燃气、通风与空调工程， 2008， 硕士

【摘要】 空气悬浮颗粒物是我国目前主要的室外大气污染物,对人体健康具有很强的危害性。由于人的一生大部分时间在室内度过,可以通过建立室内外颗粒物浓度关系的方法来评价大气悬浮颗粒物污染对室内人员的危害程度。对室内外颗粒物浓度关系的研究主要通过建立颗粒物的室内外浓度比(I/O比)来进行。影响I/O比的因素包括建筑围护结构的穿透率、通风换气、颗粒物室内源强度、沉降速率及二次悬浮等,课题主要研究对通风换气对室内外颗粒物浓度关系的影响。采用模型实验舱研究了稳态送风和动态送风条件工况,不同气流组织方式方式下,颗粒物经通风进入室内过程中,引起的室内颗粒物浓度变化过程,发现颗粒物的室内浓度分布是影响I/O比的重要因素,并提出了颗粒物龄的概念;另外,采用数值模拟的方法研究了不同粒径的颗粒物的运动规律,推荐了适合通风实验舱气流模拟的标准k ?ε双方程模型和颗粒物浓度场模拟的滑移通量模型。对于欧拉模型和拉格朗日模型的适用性也给出建议。在不存在室内源的情况下,由于大颗粒的气流间存在滑移速度,会导致I/O比大于1,同时导致颗粒物龄大于同一位置的空气龄。在由通风引起的室内颗粒物浓度增长过程中,浓度增长曲线与假设室内浓度均匀的理论曲线有很大差别,课题通过实验对质平衡方程进行修正,得到更加符合实际的理论公式。动态送风与稳态送风对于工作区I/O比变化规律没有明显影响,动态送风下送风口附近颗粒物浓度接近室外浓度所需时间较长,可以缓冲室外颗粒物浓度变化对室内的冲击。数值模拟研究结果表明,用滑移通量模型研究室内颗粒物浓度分布时,对粒径大于5μm的颗粒物,重力作用和颗粒物与气流间滑移速度不可忽略,且重力作用会导致无室内源的条件下,房间下方颗粒物I/O比大于1;对粒径小于1μm的颗粒物,重力作用和颗粒物与气流间的滑移速度可以忽略,对浓度分布没有明显影响;粒径在1μm-5μm之间的颗粒物受到滑移速度和重力作用的影响较小,在一定情况下可以忽略。气流组织方式是影响室内外颗粒物浓度关系的重要因素。数值模拟结果表明,在同侧送风和回风的气流组织方式下,下送上回的方式更加利于减小室外大颗粒对室内的影响。通风对I/O比影响的研究,以及对不同粒径颗粒物运动规律的研究,可以指导空调系统设计,最大限度的降低室外颗粒物对室内造成的危害。更多还原

【Abstract】 Airborne particles are the main atmospheric pollutant in China and have seriously harmful effect on human health. Since people spend most of their time in the rooms, the relationship between the indoor and outdoor particle concentration can be established to evaluate the harm of atmospheric particles on human health. The study on relationship between indoor and outdoor particle concentration is through establishment of indoor and outdoor particle concentration ratio (I/O Ratio). Factors affecting I/O Ratio include penetration ratio of building envelop, ventilation, indoor source, deposition rate and particle resuspension. This thesis focuses mainly on influence of ventilation on I/O Ratio.Under steady and unsteady ventilation conditions and different airflow organization, increasing of indoor particle concentration during entrance of particle from outdoor to indoor through ventilation is investigated. Indoor particle concentration distribution is found to have important influence on I/O Ratio, and a concept of particle age is brought forward herein; particle distribution characterization of different diameter is investigated through numerical simulation, standard k ?εmodel and drift flux model (DFM) are recommended for simulation of turbulence and particle concentration distribution, respectively. Applicability of Eulerian model and Lagrangian model is analyzed.The I/O Ratio can be greater than 1 with absence of indoor source, and particle age is greater than air age of the same position due to slip velocity between airflow and particle. In the process of particle concentration increase caused by ventilation, concentration increasing curve is different from theoretical curve, mass balance equation is thus revised to be more accordant with test value. Steady and unsteady ventilation have the same effect on increasing rate of I/O Ratio on occupant area. A longer time is needed for the particle concentration to reach the outdoor value around the air inlet under unsteady than steady ventilation, decreasing the influence of outdoor particle concentration variation on indoor.Gravity and slip velocity between airflow and particle can not be neglected for particles with diameter larger than 5μm through the result of numerical simulation by DFM, and I/O Ratio near floor of a room can be greater than 1 without indoor source due to gravity. Gravity and slip velocity between airflow and particles are negligible and have no effect on concentration distribution for particles with diameter smaller than 1μm. For particles with diameter 1μm-5μm, gravity and slip velocity between airflow and particles are only negligible under certain circumstance.Airflow organization has great effect on relationship between indoor and outdoor particle concentration. Airflow organization of downward supply and upward discharge is more effective in decreasing influence of outdoor larger particles on indoor.Research on the influence of ventilation on I/O Ratio and moving characterization of particles with different diameter can provide guideline for air conditioning system design to minimize the harmful effect of outdoor particle concentration on indoor.更多还原