McKernan John L, Ellenbecker Michael J, Holcroft Christina A, Petersen Martin R
National Institute for Occupational Safety and Health, Division of Surveillance, Hazard Evaluation and Field Studies, 4676 Columbia Parkway, MS-R14, Cincinnati, OH 45226, USA.
Ann Occup Hyg. 2007 Jun;51(4):357-69. doi: 10.1093/annhyg/mem016. Epub 2007 May 22.
Exothermic or heated processes create potentially unsafe work environments for an estimated 5-10 million American workers each year. Excessive heat and process contaminants have the potential to cause adverse health effects in exposed workers. Owing to the potential hazards, engineering controls are recommended for these processes. Our understanding of heat transfer and meteorological theories, and their applications for engineering controls have evolved since seminal work was published by Hemeon in 1955. These refined theories were reviewed and used to develop a proposed equation to estimate buoyant plume mean velocity. Mean velocity is a key parameter used to estimate the plume volumetric flow required for controlling effluents from exothermic processes. Subsequent to developing the proposed equation, plume velocity data were collected with a thermal anemometer for a model exothermic process in the laboratory, and an actual exothermic process in the field. Laboratory and field results were then compared to solutions provided by the proposed, American Conference of Governmental Industrial Hygienists (ACGIH), and Hemeon mean velocity equations. To determine which equation most closely matched the laboratory and field data, either t-tests or Wilcoxon Signed Rank tests were conducted (based on examination of data normality) to determine the difference between collected data and solutions from the proposed, ACGIH, and Hemeon equations. Median differences and P-values from Wilcoxon Signed Rank tests (nonparametric) indicate that the ACGIH mean velocity equation provides significantly different estimates from the laboratory and the field mean velocity data. However, the proposed and Hemeon equation provided solutions that were not significantly different from the collected data. These results were unexpected due to the similar developmental backgrounds between the ACGIH and Hemeon equations. Findings indicate that radiant heat flux is an important consideration when using horizontal plate heat transfer equations to estimate plume mean velocity over the range of parameters investigated. Results indicate that the mean velocity equation currently recommended by ACGIH is not as accurate as either the proposed or Hemeon equations over the range of parameters investigated.
放热或加热过程每年为约500万至1000万美国工人创造了潜在不安全的工作环境。过高的热量和工艺污染物有可能对接触到的工人造成不良健康影响。由于存在潜在危害，建议对这些过程采取工程控制措施。自1955年赫米恩发表开创性著作以来，我们对传热和气象理论及其在工程控制中的应用的理解不断发展。对这些完善的理论进行了回顾，并用于推导一个估计浮力羽流平均速度的建议方程。平均速度是用于估计控制放热过程排放所需羽流体积流量的关键参数。在推导建议方程之后，使用热风速仪在实验室的一个模型放热过程和现场的一个实际放热过程中收集了羽流速度数据。然后将实验室和现场结果与建议方程、美国政府工业卫生学家会议（ACGIH）和赫米恩平均速度方程提供的解进行比较。为了确定哪个方程与实验室和现场数据最匹配，进行了t检验或威尔科克森符号秩检验（基于数据正态性检验），以确定收集到的数据与建议方程、ACGIH方程和赫米恩方程的解之间的差异。威尔科克森符号秩检验（非参数）的中位数差异和P值表明，ACGIH平均速度方程提供的估计值与实验室和现场平均速度数据有显著差异。然而，建议方程和赫米恩方程提供的解与收集到的数据没有显著差异。由于ACGIH方程和赫米恩方程的发展背景相似，这些结果出乎意料。研究结果表明，在研究的参数范围内，使用水平板传热方程估计羽流平均速度时，辐射热通量是一个重要的考虑因素。结果表明，在所研究的参数范围内，ACGIH目前推荐的平均速度方程不如建议方程或赫米恩方程准确。
