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Heat transfer through clothing is an important topic related to thermal comfort in environmental engineering and functional clothing design. The total heat transmitted through clothing is commonly considered as the sum of the dry heat transfer and the evaporative heat transfer. Clothing thermal insulation measured in a nonperspiring condition, e.g., on a dry thermal manikin, is frequently used to calculate the dry heat transfer when the body is perspiring or even sweating heavily. The effect of perspiration on clothing thermal insulation with respect to dry heat transfer is not well understood, although it is widely speculated that perspiration reduces thermal insulation by wetting clothing assemblies. In this investigation, clothing thermal insulation with very low perspiration and very heavy perspiration is measured using a novel perspiring fabric thermal manikin. Clothing thermal insulation decreases during perspiration, and the amount of reduction varies from 2 to 8%, as related to water accumulation within clothing ensembles. This finding suggests the "after chill" effect of wearers after heavy exercise may not only be caused by heat absorption due to the desorption and evaporation of water within clothing, but also to reduced clothing thermal insulation. Also, for clothing that can absorb a large amount of moisture during sweating, clothing thermal insulation measured on dry manikins may need to be corrected when used for calculating dry heat loss (sometimes used for calculating moisture vapor resistance) on a sweating manikin and predicting thermal comfort during sweating.Clothing thermal insulation is an important parameter in thermal comfort. It is used to determine the heat stress of a clothed person in a hot environment in terms of the required evaporation for thermal equilibrium, required sweat rate, and skin wetness (ISO 7933 [8], Parsons [ I3]), and to determine cold stress in a cold condition in terms of the required insulation (Holmer [6]). It is also an important measure of the effectiveness of clothing functional design and suitability of clothing systems (Mecheels and Umbach [ I 1 ]) for intended end uses.In the past, there has been considerable research on the effects of human physical activities and climatic conditions, (i.e., wind and surrounding temperature) on clothing thermal insulation (Lotens and Havenith [9], Holmer et al. [7], Havenith et al. [5], Sari and Berger [14], and Fan and Keighley [3]), but there has been comparatively little work on the effect of human perspiration on insulation. Consequently, clothing thermal insulation measured or predicted in nonperspiring (or dry) conditions is used to calculate the heat transfer through clothing when the body is perspiring (or sweating) with the possibility of error.

Abstract:A novel breathable piezoelectric membrane has been developed by growing zinc oxide (ZnO) nanorods on the surface of electrospun poly(vinylidene fluoride) (PVDF) nanofibers using a low-temperature hydrothermal method. Significant improvement in the piezoelectric response of the PVDF membrane was achieved without compromising breathability and flexibility. PVDF is one of the most frequently used piezoelectric polymers due to its high durability and reasonable piezoelectric coefficient values. However, further enhancement of its piezoelectric response is highly desirable for sensor and energy-harvester applications. Previous studies have demonstrated that piezoelectric ceramic and polymer composites can have remarkable piezoelectric properties and flexibility. However, devices made of such composites lack breathability and some present health risks in wearable applications for containing heavy metals. Unlike other piezoelectric ceramics, ZnO is non-toxic material and has been widely used in many applications including cosmetics. The fabrication of ZnO@PVDF porous electrospun membrane involves a simple low-temperature ZnO growth in aqueous solution, which does not weaken the polarization of PVDF created during electrospinning in the high electric field.