When clothing is immersed in water, the water will rapidly occupy the internal void of the clothing, and the air layer inside the clothing will disappear, which leads to a drastic reduction in the thermal resistance of the clothing. To calculate the thermal resistance of clothing under fully wet conditions, a novel serial method was proposed. The method is a combination of the thermal resistance of water and the thermal resistance of wet fibers. To verify the effectiveness of the new method, the thermal resistances of three typical suits under fully wet conditions were measured. Three typical suits, a summer suit (T-shirt + shorts), a spring suit (sportswear + sweatpants), and a winter suit (cotton coat + wool pants), were chosen as test objects. The thermal resistances of these suits under fully wet conditions were measured in an experimental water tank built in a chamber using a thermal manikin, “Walter.” The thermal resistance measurement in this study can eliminate the experimental error caused by the evaporation of water so as to obtain an accurate thermal resistance measurement. According to the experimental results and the model, the key factors affecting the thermal resistance under fully wet conditions were thickness ( Rpearson = 0.992), porosity ( Rpearson = 0.980), and moisture content ( Rpearson = 0.964). Compared to other thermal resistance prediction models, the prediction results by the novel method were more consistent with the measured results, with all deviations less than 10% and the correlation value R2 = 0.998.
Life jackets are essential life-saving devices, and also play an important role in the thermal protection of drowning victims in cold water. To better understand the thermal performance of the combinations of suits and life jackets in water, a thermal manikin named “Walter” in a water tank was used to simulate the environment surrounding the drowning person. Three sets of suits and three sets of life jackets form a total of 12 test combinations to simulate the clothes worn by drowning people. The thermal resistance of 12 combinations in water were measured according to ISO 15831 and heat transfer coefficients for the chest, back, upper arm, arm, thigh and leg of the 12 test combinations were calculated and compared. Results showed that the combinations of the clothes and life jacket efficiently lowered conduction and convective heat transfer coefficients in the water. The total thermal resistance of the 12 test combinations ranged from 0.011 to 0.054°C · m2/W. The post-hoc analysis revealed that the conductive thermal resistances of the clothing combinations with life jackets were all elevated compared to those of the clothing combinations without life jackets ( p < 0.001), showing that life jackets provide better thermal insulation. The linear regression indicated that the conductive thermal resistance of the test combination had a considerable impact on the convective heat transfer coefficient. This study helps to establish the systematic study of the thermal protection performance of life jackets.
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