Elson John, Eckels Steve
Department of Mechanical and Nuclear Engineering, Institute for Environmental Research, Kansas State University, 64 Seaton Hall, Manhattan, KS, 66506, USA.
Department of Mechanical and Nuclear Engineering, Institute for Environmental Research, Kansas State University, 64 Seaton Hall, Manhattan, KS, 66506, USA.
J Therm Biol. 2018 Dec;78:343-351. doi: 10.1016/j.jtherbio.2018.09.014. Epub 2018 Oct 5.
Quantifying the impact of clothing thermal and evaporation resistance is essential to providing representative boundary conditions for physiological modeling. In many models, sweat is assumed to drip off the skin surface to the environment and is not captured in clothing. In high metabolic rate and high temperature and humidity conditions the sweat produced by the body has the potential to saturate semipermeable clothing ensembles, changing the assumptions of the model. Workers, athletes and soldiers commonly wear encapsulating versions of such clothing to protect against environmental hazards. A saturated clothing model is proposed based on the ASHRAE two-node model using a saturated spot element in parallel with the existing method to account for sweat absorbed in the clothing. The work uses fundamental heat and mass transfer principles, modifying the existing formula using clothing measurements and basic assumptions. The effectiveness of the model is demonstrated by comparing the predictions of the original and proposed models, to the results of 21 soldiers exercising. The soldiers wore combat pants and shirt, helmet, gloves, shoes, socks, and underwear, and walked in a thermal chamber for 2 h at 42.2 °C dry bulb temperature, 54.4 °C wet bulb temperature, 20% relative humidity, and airspeed of 2 m/s. Core temperature, seven skin temperatures, heart rate, and total sweat loss were measured. The original model provides an average core temperature difference compared with the human subject results of 1.31 °C (SD = 0.557 °C) while the modified model improves the final prediction of core temperature to within an average of 0.15 °C (SD = 0.383 °C). The new model shows an improvement in the prediction of human core temperature under the tested conditions where dripping sweat will saturate clothing. The format can be used in multi-segmented thermal models and can continue to be developed and improved as more information on wetted clothing properties become available.
量化服装的热阻和蒸发阻力的影响对于为生理模型提供具有代表性的边界条件至关重要。在许多模型中，汗液被假定从皮肤表面滴落到环境中，而不会被服装截留。在高代谢率以及高温高湿条件下，人体产生的汗液有可能使半透性服装湿透，从而改变模型的假设。工人、运动员和士兵通常会穿着此类服装的密封版本以抵御环境危害。基于美国供暖、制冷与空调工程师协会（ASHRAE）的双节点模型，提出了一种饱和服装模型，该模型使用一个饱和点单元与现有方法并行，以考虑服装中吸收的汗液。这项工作运用了基本的传热传质原理，通过服装测量和基本假设对现有公式进行了修改。通过将原始模型和所提出模型的预测结果与21名正在锻炼的士兵的结果进行比较，证明了该模型的有效性。这些士兵穿着作战裤和衬衫、头盔、手套、鞋子、袜子和内衣，在温度为干球温度42.2°C、湿球温度54.4°C、相对湿度20%、风速2 m/s的热室中行走2小时。测量了核心温度、七个皮肤温度、心率和总出汗量。与人体受试者的结果相比，原始模型的平均核心温度差为1.31°C（标准差=0.557°C），而改进后的模型将核心温度的最终预测提高到平均0.15°C以内（标准差=0.383°C）。新模型在汗液会使服装饱和的测试条件下，对人体核心温度的预测有了改进。该模型形式可用于多段热模型，并且随着更多关于湿衣服特性的信息可用，可继续进行开发和改进。
