Comparing objects for human movement simulation regarding its air flow disturbance at local exhaust ventilation
Comparing objects for human movement simulation regarding its air flow disturbance at local exhaust ventilation
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比较人体运动模拟对象在局部排气通风时的气流扰动
DOI：
10.1016/j.enbuild.2021.111117
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发表时间：
2021
影响因子：
6.7
通讯作者：
Abolfazl Hayati
中科院分区：
文献类型：
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作者：
Mohammadbagher Mahaki;M. Mattsson;M. Salmanzadeh;Abolfazl Hayati
室内人员和其他物体的运动可能影响局部排气通风罩附近的气流模式和速度，从而影响通风罩清除局部排放污染物的能力和通风能量需求。在本研究中，对这种扰动效应进行了实验和数值研究，分别由人体大小的板、圆柱和详细的人体模型组成的运动在排气罩附近来回运动。在实验部分，使用三维声速计测量发动机罩开口前的风速。数值模拟采用动态网格处理物体运动。数值计算结果与实验结果进行了比较，得到了空气流场的补充结果。结果表明，物体运动产生的湍流在排气罩近场存在明显的风速峰值，既有辅助气流的，也有阻碍气流的。事实证明，在板块运动的情况下，产生的湍流，特别是那些峰值，比圆柱体和假人运动的情况下要大得多。综上所述，运动的圆柱体比运动的平板更能代表人体的运动，因此，在目前规定平板为运动物体的一些测试标准中，使用圆柱体是更好的。引入负速度百分比（Percentage of Negative Velocity， PNV）参数来评价局部排气系统的捕集效率。PNV表示在想象的污染物释放点，空气流被引导离开排气罩的时间百分比。该研究包括PNV值显著高于零的测试案例，这表明排气罩的捕获效率受到强烈影响。人为引起的紊流会导致这种反向气流和整体阻碍引擎盖吸力，可以通过提高排气流量来抵消，但随后会产生更高的能耗。
The movement of people and other objects indoors may affect airflow patterns and velocities near local exhaust ventilation hoods, and consequently has influence on the hoods’ ability to remove locally emitted contaminants and on ventilation energy requirements. In this study, such disturbance effects have been studied experimentally and numerically, with the movements consisting of a human-sized plate, cylinder and detailed manikin, respectively, making back-and-forth movements near an exhaust hood. In the experimental part of the study, a 3-D sonic anemometer was used to measure air velocity in front of the hood opening. The numerical simulations used dynamic mesh to handle object movements. The numerical results were validated against the experimental ones and yielded supplementary results on the air flow field. The results show that the turbulence produced by the objects movements included marked air velocity peaks – both assisting and impeding the suction flow – in the near field of the exhaust hood. The generated turbulence, and particularly those peaks, proved substantially larger in the case of plate movement than with cylinder and manikin movement. Overall the results indicate that a moving cylinder represents human movement better than a moving plate, and thus that it’s better to use a cylinder in some test standards that now stipulate a plate as moving object. A Percentage of Negative Velocity (PNV) parameter was introduced for assessing the capture efficiency of the local exhaust system. The PNV represents the percentage of time that the air flow is directed away from the exhaust hood in an imagined point of contaminant release. The study includes test cases where the PNV values were significantly above zero, suggesting a strong effect on the capture efficiency of the exhaust hood. Human induced turbulence that cause such reverse air flows and overall impedes hood suction may be counteracted by enhanced exhaust flow rate, but then at higher energy consumption.