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首页> 外文学位 >Effects of 0 degrees cross draft velocity and the presence of a table and manikin on midline velocities in front of a rectangular capture hood.
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Effects of 0 degrees cross draft velocity and the presence of a table and manikin on midline velocities in front of a rectangular capture hood.

机译：0度横吃水速度以及桌子和人体模型的存在对矩形捕获罩前面的中线速度的影响。

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摘要

Local Exhaust Ventilation is a primary method used by industrial hygiene and engineering practitioners to eliminate or reduce exposures to airborne contaminants. Capture hoods are an important component of many ventilation systems. Currently, the exhaust airflow required for these hoods is based on exceeding a specified minimum velocity at a point just beyond the greatest distance of the source from the front of the hood. Estimating the expected velocity at any point along the midline of the hood (Vx) is currently done using one of many predictive equations developed since the 1930's. There are two problems with these equations: (1) they are based on unrealistically ideal conditions, and (2) they disagree substantially with each other.This study measured the values of Vx along the midline of the hood face at distances of 1--14 inches in front of a capture hood. This was done for the ideal conditions used to develop the previously published equations. In addition, velocities were measured for realistic conditions, including all combinations of 3 0° cross-draft velocities and the presence or absence of both a manikin and work table. All tests were done in a large wind tunnel, measuring Vx with a particle image velocimeter. The objective was to compare Vx between ideal and non-ideal conditions and to published models.For most test conditions, Vx declined nearly exponentially with increasing distance (x), from the hood face. Log-transformation revealed two different slopes at x=1" to 8" and x=8" to 14", for ideal conditions. The different slopes suggest that factor(s) other than x become important as Vx decreases with distance.The experimental results found substantial and statistically significant effects (p0.001) for 3 levels of cross draft velocities (Vcross), the presence of a manikin, the presence of a work table, and all interactions of those factors. The effects were most pronounced at distances greater than 10" from the hood face. At that range, and Vcross=4 fpm, the presence of a table increased Vx by an average of 60% while the presence of a manikin decreased Vx by an average of 12%. At Vcross=50 fpm, the presence of a table increased Vx on average by 2.3 times Vx for ideal conditions. However, V cross made little difference in Vx measured in the presence of a manikin.None of the predictive models evaluated here accurately predicted V x under the realistic conditions tested in this study. A satisfactory model will have to include terms for Vcross and the presence or absence of a work table and a worker.
机译：局部排气通风是工业卫生和工程从业人员用来消除或减少空气传播污染物的主要方法。通风橱是许多通风系统的重要组成部分。当前，这些罩子所需的排气流基于在超过源距罩子前部的最大距离的点处超过指定的最小速度。目前，估计引擎盖中线（Vx）沿任一点的预期速度是使用自1930年代以来开发的许多预测方程式之一进行的。这些方程式有两个问题：（1）它们基于不切实际的理想条件，（2）它们彼此之间大相径庭。这项研究测量了沿引擎盖面中线在1-距离处的Vx值-捕获罩前14英寸。这样做是为了开发先前发布的方程式的理想条件。此外，还测量了实际条件下的速度，包括3 0度横向风速的所有组合以及人体模型和工作台的有无。所有测试均在大型风洞中进行，用粒子图像测速仪测量Vx。目的是比较理想状态和非理想状态之间的Vx并与已发布的模型进行比较。在大多数测试条件下，Vx距引擎盖表面的距离（x）随距离（x）的增加呈指数下降。对数变换揭示了理想条件下x = 1“至8”和x = 8“至14”的两个不同斜率。不同的斜率表明，随着Vx随距离的减小，x以外的其他因素变得很重要。实验结果发现，在3种横向通风速度（Vcross）以及人体模型的存在下，具有显着和统计学上显着的影响（p <0.001） ，工作表的存在以及这些因素的所有相互作用。在距引擎盖表面大于10英寸的距离处，效果最为明显。在此范围内，Vcross = 4 fpm，桌子的存在使Vx平均增加了60％，而人体模型的存在使Vx平均减少了在Vcross = 50 fpm时，在理想条件下，工作台的存在会使Vx平均增加2.3倍，但在人体模型存在的情况下，V cross对Vx的影响很小。这里要在本研究中测试的实际条件下准确预测V x，令人满意的模型必须包括Vcross的术语以及工作台和工人的存在与否。

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  • 作者

    Lewis, Braxton V.;

  • 作者单位

    West Virginia University.;

  • 授予单位 West Virginia University.;
  • 学科 Health Sciences Occupational Health and Safety.Engineering Mechanical.
  • 学位 M.S.
  • 年度 2010
  • 页码 83 p.
  • 总页数 83
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:36:56

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