Liu X, Holmér I
Division of Industrial Ergonomics, Luled, University of Technology, Sweden.
Appl Human Sci. 1997 May;16(3):107-13. doi: 10.2114/jpa.16.107.
The prime purpose of a safety helmet is to protect against occupational hazards. However, thermal comfort is one important ergonomics requirement for a helmet to be accepted by its wearer. To design and manufacture a thermally comfortable helmet, a method for testing and evaluating the thermal properties is essential. Research has long focused on the evaluation of dry heat transfer (conduction, convection and radiation). Evaporative heat transfer was not much addressed. In order to analyze the wet heat transfer (evaporation) component, a sweating thermal head manikin has been used. In this study the method has been further improved by constructing a new sweating head manikin. The surface of the head manikin is divided into five zones which can provide more detailed information about the environmental effects on the heat transfer from the head when a helmet is worn. Water supply (simulated sweating) is also improved by use of an electronic pumping system which provides a steady and adjustable flow rate of water to the head manikin. Experiments were conducted within a climatic chamber with this improved method under different test conditions: the ambient temperature and the head manikin surface temperature are set at the same level: 34 +/- 0.5 degrees C; two levels of head surface wettedness: 0.44 and 1.0; two levels of ambient humidity: 30% and 60%; and two levels of wind speed: 0.4 m/s and 1.0 m/s. Seven different helmets were used in the experiments. The results showed that the improved method revealed more detailed information about the evaporative heat transfer; it is easier to use and control; less error is involved with the measurement.
安全帽的主要目的是防范职业危害。然而，热舒适性是安全帽被佩戴者接受的一项重要人机工程学要求。为了设计和制造热舒适的安全帽，一种测试和评估热性能的方法至关重要。长期以来，研究一直集中在干热传递（传导、对流和辐射）的评估上。蒸发散热方面涉及不多。为了分析湿热传递（蒸发）成分，使用了出汗热头模型。在本研究中，通过构建一个新的出汗头模型，该方法得到了进一步改进。头模型的表面被划分为五个区域，当佩戴安全帽时，这些区域可以提供有关环境对头部热传递影响的更详细信息。通过使用电子泵送系统改进了供水（模拟出汗），该系统为头模型提供稳定且可调节的水流速。在气候室内使用这种改进方法在不同测试条件下进行了实验：环境温度和头模型表面温度设定在同一水平：34±0.5摄氏度；头表面湿润度的两个水平：0.44和1.0；环境湿度的两个水平：30%和60%；以及风速的两个水平：0.4米/秒和1.0米/秒。实验中使用了七种不同的安全帽。结果表明，改进后的方法揭示了有关蒸发散热的更详细信息；它更易于使用和控制；测量误差更小。
