Sampling efficiency of modified 37-mm sampling cassettes using computational fluid dynamics.
Sampling efficiency of modified 37-mm sampling cassettes using computational fluid dynamics.
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DOI：
10.1080/15459624.2015.1091961
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发表时间：
2016
影响因子：
2
通讯作者：
Volckens J
中科院分区：
文献类型：
--
作者：
Anthony TR;Sleeth D;Volckens J
在美国，大多数工业卫生从业者继续依赖于封闭式盒式磁带（CFC）来评估工人暴露于有害粉尘，主要是因为易于使用、成本和熟悉度。然而，使用这种经典采样器测量的质量浓度低估了在整个可吸入颗粒物质量（IPM）尺寸范围内（空气动力学直径高达100 µm）对较大颗粒的暴露。为了研究是否可以重新设计当前的37 mm入口帽以更好地满足IPM采样标准，开发了计算流体动力学（CFD）模型，并确定了与CFC入口帽的各种修改相关的颗粒采样效率。流体流动（标准k-ε湍流模型）和颗粒传输（层流轨迹，1至116 µm）的模拟是在迎风方向的缓慢移动空气（0.2 m s−1）中使用10 L min−1的采样流速进行的。评估了七种入口形状和三种入口直径的组合，作为替代当前37 mm入口盖的候选方案。对于给定的入口几何形状，对于100 µm以下的颗粒，入口直径之间的采样器效率差异平均小于1%，但对于扁平入口盖，发现最大开口可将116 µm颗粒的效率提高14%。对于侧壁延伸超过当前37毫米氟氯化碳外唇尺寸的采样器入口，发现采样器效率大幅降低。基于37 mm CFC尺寸的入口帽，具有扩展的15 mm入口，提供了与迎风人类吸气效率的最佳一致性。取样器的效率增加了一个平坦的入口或一个薄的中心唇相邻的新扩大的入口。这项工作提供了大量的采样效率估计作为个人气溶胶采样器的粒径和入口几何形状的函数。
In the U.S., most industrial hygiene practitioners continue to rely on the closed-face cassette (CFC) to assess worker exposures to hazardous dusts, primarily because ease of use, cost, and familiarity. However, mass concentrations measured with this classic sampler underestimate exposures to larger particles throughout the inhalable particulate mass (IPM) size range (up to aerodynamic diameters of 100 µm). To investigate whether the current 37-mm inlet cap can be redesigned to better meet the IPM sampling criterion, computational fluid dynamics (CFD) models were developed, and particle sampling efficiencies associated with various modifications to the CFC inlet cap were determined. Simulations of fluid flow (standard k-epsilon turbulent model) and particle transport (laminar trajectories, 1 through 116 µm) were conducted using sampling flow rates of 10 L min−1 in slow moving air (0.2 m s−1) in the facing-the-wind orientation. Combinations of seven inlet shapes and three inlet diameters were evaluated as candidates to replace the current 37-mm inlet cap. For a given inlet geometry, differences in sampler efficiency between inlet diameters averaged less than 1% for particles through 100 µm, but the largest opening was found to increase the efficiency for the 116 µm particles by 14% for the flat inlet cap. A substantial reduction in sampler efficiency was identified for sampler inlets with side walls extending beyond the dimension of the external lip of the current 37-mm CFC. The inlet cap based on the 37-mm CFC dimensions with an expanded 15-mm entry provided the best agreement with facing-the-wind human aspiration efficiency. The sampler efficiency was increased with a flat entry or with a thin central lip adjacent to the new enlarged entry. This work provides a substantial body of sampling efficiency estimates as a function of particle size and inlet geometry for personal aerosol samplers.