湿球黑球温度对高温环境的适用性及安全热暴露时长的研究

发布时间：2018-08-29 10:31

【摘要】：随着社会文明程度的进步，，劳动者的生产作业环境越来越受到重视，高温环境对操作人员健康的直接危害及对作业安全的潜在威胁急需得到解决。热暴露下人体生理指标变化趋势、安全热暴露时长及对应的生理指标限值是评价热负荷及人体热应激程度的主要依据。简单、易计算且能准确反映人体热耐受能力的热应力评价指标是人们一直在探寻的研究方向。本文通过实验室实验研究，对具有相同WBGT指数的干热环境和湿热环境两种不同环境类型对人体造成的热应激情况进行研究，以验证WBGT指数对于我国劳动人群在这两类环境中的适用性。论文在人体热平衡的理论基础上对人体热应激变化的三个状态阶段进行分析，人体热应激程度的变化过程可以根据人体能否维持热平衡及生理参数是否超过安全限值分为三个状态阶段，分别为热平衡状态、缓慢蓄热状态、急剧蓄热状态。根据三大类指标特点提出了将三大类指标与人体热应激变化的三个状态阶段相结合的应用策略：将间接反映生理热应激且安全限值相对保守但应用便捷、易测的“经验型”指标用于第一阶段的评价，在热负荷超过第一状态阶段限值时，将能直接反映生理热应激但相对复杂的“生理型”和“理论型”指标应用于第二状态阶段，当生理热应激超过安全限值时则要求作业人员停止继续高温作业。本实验研究在人工气候室中设计了三组实验工况组，分别为在WBGT=26℃时进行极高代谢水平活动，在WBGT=28℃时进行高代谢率水平活动，在WBGT=30℃时进行中代谢率水平活动。根据重庆市气象特征，各工况组再分别控制相对湿度为30%和60%，从而营造干热环境和湿热环境的两种对比工况。通过自愿原则筛选出长期从事体力劳动的男性参与所有工况实验，共进行了60人次的实验。通过对各工况组的干热环境和湿热环境之间生理参数的差异分别进行显著性检验，结果表明当WBGT=30℃时，受试者在干热环境下的直肠温度显著高于湿热环境下的直肠温度，当WBGT=26℃时，受试者在干热环境下的排汗速率显著大于湿热环境下的排汗速率，且所有工况组中受试者在干热环境下皮肤温度显著高于湿热环境下的皮肤温度。以直肠温度为38℃作为热暴露安全阈值确定安全热暴露时长TT，以心率阈值来确定安全热暴露时长THR，取两者较小值作为受试者持续作业时的安全热暴露时长，且论文对各工况组两类环境之间的热暴露时长采用生存分析方法进行差异性检验，结果表明：WBGT=30℃和28℃时工况组中两类环境之间受试者的TT具有显著差异，而各工况组中两类环境之间的THR不存在显著差异。以上检验结果表明即使WBGT指数、代谢率及个体因素都相同时，相同的WBGT指数并不总能表征相同的热负荷、生理热应激和安全热暴露时长。相对于湿热环境，相同的WBGT指数可能会低估干热工况下的热负荷和生理热应激，需在后期研究中针对不同高温环境类型调整WBGT中黑球温度和自然湿球温度的权重系数。此外，通过将本实验工况与ISO7243和ACGIH持续工作的安全阈值曲线进行比较可知，受试者的耐热性并不一定比ISO7243和ACGIH以欧美人群实验为基础得出的耐热性要高。且由确定的安全热暴露时长可知，受试者在GB/T17244-1998中“差”等级高温环境下活动时无法实现热平衡和持续性劳动，因此，针对这类等级高温环境下的作业应该给出劳动者的安全热暴露时长作为保护劳动者生理参数不超标的参考。可在后期研究中对“好”、“中”等级工况进行研究，即可判断出我国劳动者相比于欧美人群的耐热性高低，并能确定适用于我国劳动者的WBGT-M安全限值曲线和安全热暴露时长曲线。
[Abstract]:With the progress of social civilization, more and more attention has been paid to the working environment of workers. The direct harm of high temperature environment to operators'health and the potential threat to work safety need to be solved urgently. Simple, easy to calculate and accurately reflect the human thermal tolerance of thermal stress evaluation index is the research direction of people have been exploring. This paper through laboratory experiments, with the same WBGT index of dry and hot environment and humid and hot environment of two different types of environmental heat stress on human body caused by heat. A case study was conducted to verify the applicability of WBGT index to China's working population in these two environments.
Based on the theory of human thermal balance, this paper analyzes the three stages of human thermal stress change. The process of human thermal stress change can be divided into three stages according to whether the human body can maintain the thermal balance and whether the physiological parameters exceed the safety limit, namely, the state of thermal balance, the state of slow thermal storage and the state of rapid thermal storage. According to the characteristics of the three categories of indicators, the application strategy of combining the three categories of indicators with the three stages of human heat stress change is put forward. The "empirical" indicators, which indirectly reflect physiological heat stress and the safety limit is relatively conservative but convenient to use, are used in the evaluation of the first stage and are easy to measure when the heat load exceeds the first stage. The physiological and theoretical indexes, which can directly reflect physiological heat stress but are relatively complex, are applied to the second stage. When the physiological heat stress exceeds the safety limit, the workers are required to stop working at high temperature.
In this study, three groups of experimental conditions were designed in an artificial climate chamber. They were exceptionally high metabolic level activities at WBGT = 26 C, high metabolic rate activities at WBGT = 28 C, and medium metabolic rate activities at WBGT = 30 C. According to the meteorological characteristics of Chongqing, the relative humidity was controlled at 30% and 60% respectively. In order to create a dry-hot environment and a humid-hot environment of the two contrastive conditions, through the principle of voluntary selection of long-term manual labor of men to participate in all the working conditions of the experiment, a total of 60 experiments.
The results showed that the temperature of the rectum in the dry-hot environment was significantly higher than that in the humid-hot environment when WBGT was 30, and the sweating rate in the dry-hot environment was significantly higher than that in the humid-hot environment when WBGT was 26. The transpiration rate in the environment was significantly higher than that in the humid and hot environment in all working groups. The rectal temperature was 38 C as the safety threshold of thermal exposure to determine the safe thermal exposure time TT, and the heart rate threshold to determine the safe thermal exposure time THR. The results showed that there was significant difference in TT between the two environments at WBGT=30 C and 28 C, while there was no significant difference in THR between the two environments.
The above results show that the same WBGT index does not always represent the same heat load, physiological heat stress and safe heat exposure time even when the WBGT index, metabolic rate and individual factors are the same. The weight coefficients of black sphere temperature and natural wet bulb temperature in WBGT are adjusted for different types of high temperature environment.
In addition, by comparing the experimental conditions with the safety threshold curves of ISO7243 and ACGIH, we can see that the subjects'thermal tolerance is not necessarily higher than that of ISO7243 and ACGIH, which are based on the European and American population experiments. Thermal balance and persistent labor can not be achieved when working in warm environment. Therefore, the safe exposure time of workers should be given as a reference to protect the physiological parameters of workers. Compared with European and American people, the heat tolerance of the affected persons is higher and lower, and WBGT-M safety limit curve and safety heat exposure time curve suitable for Chinese workers can be determined.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：R134.3;X968

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