Bröde Peter, Havenith George, Wang Xiaoxin, Candas Victor, den Hartog Emiel A, Griefahn Barbara, Holmér Ingvar, Kuklane Kalev, Meinander Harriet, Nocker Wolfgang, Richards Mark
University of Dortmund, Ardeystr. 67, 44139, Dortmund, Germany.
Eur J Appl Physiol. 2008 Sep;104(2):341-9. doi: 10.1007/s00421-007-0629-y. Epub 2007 Dec 15.
In order to assess the non-evaporative components of the reduced thermal insulation of wet clothing, experiments were performed with a manikin and with human subjects in which two layers of underwear separated by an impermeable barrier were worn under an impermeable overgarment at 20 degrees C, 80% RH and 0.5 ms(-1) air velocity. By comparing manikin measurements with dry and wetted mid underwear layer, the increase in heat loss caused by a wet layer kept away from the skin was determined, which turned out to be small (5-6 W m(-2)), irrespective of the inner underwear layer being dry or wetted, and was only one third of the evaporative heat loss calculated from weight change, i.e. evaporative cooling efficiency was far below unity. In the experiments with eight males, each subject participated in two sessions with the mid underwear layer either dry or wetted, where they stood still for the first 30 min and then performed treadmill work for 60 min. Reduced heat strain due to lower insulation with the wetted mid layer was observed with decreased microclimate and skin temperatures, lowered sweat loss and cardiac strain. Accordingly, total clothing insulation calculated over the walking period from heat balance equations was reduced by 0.02 m(2) degrees C W(-1) (16%), while for the standing period the same decrease in insulation, representing 9% reduction only showed up after allowing for the lower evaporative cooling efficiency in the calculations. As evaporation to the environment and inside the clothing was restricted, the observed small alterations may be attributed to the wet mid layer's increased conductivity, which, however, appears to be of minor importance compared to the evaporative effects in the assessment of the thermal properties of wet clothing.
为了评估湿衣物降低热绝缘性的非蒸发成分，在20摄氏度、相对湿度80%、风速0.5米每秒的条件下，使用人体模型和人体受试者进行了实验，实验中在不透水的外衣下穿着两层由不透水屏障隔开的内衣。通过比较人体模型在干燥和浸湿中间内衣层时的测量结果，确定了远离皮肤的湿层导致的热损失增加量，结果发现该增加量很小（5 - 6瓦每平方米），无论内层内衣是干燥还是浸湿的，并且仅为根据重量变化计算出的蒸发热损失的三分之一，即蒸发冷却效率远低于1。在对八名男性进行的实验中，每个受试者参加了两个阶段的实验，中间内衣层分别为干燥或浸湿状态，他们在前30分钟静止站立，然后进行60分钟的跑步机运动。观察到由于浸湿中间层导致的隔热性降低，热应激减轻，同时微气候和皮肤温度降低、汗液流失减少以及心脏应激减轻。因此，根据热平衡方程计算得出的步行期间的总衣物隔热性降低了0.02平方米摄氏度每瓦（16%），而在站立期间，同样的隔热性降低（仅9%）在考虑到计算中较低的蒸发冷却效率后才显现出来。由于向环境和衣物内部的蒸发受到限制，观察到的微小变化可能归因于湿中间层增加的热导率，然而，与评估湿衣物热性能时的蒸发效应相比，这似乎不太重要。
