Effects of clothing and fibres properties on the heat and mass transport, for different body heat/sweat releases

• Autor(a) principal: S. F. Neves
• Data de Publicação: 2017
• Outros Autores: J. B. L. M. Campos, T. S. Mayor
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: https://hdl.handle.net/10216/102683

Clothing plays a key role in the capacity of the body to adapt to the surrounding thermal environments. Thus, it is critically important to have a solid understanding of the effects of clothing and fibres properties on the body exchange rates. To this end, a detailed transfer model was implemented to analyse the effect of several textiles characteristics (outer surface emissivity, tortuosity, and fraction of fibre) and fibre properties (affinity with water, coefficient of water diffusion in the fibres, thermal conductivity, density, and specific heat), on the heat and mass transfer through multilayer clothing, for different intensities of heat/sweat release. The temperature and humidity predictions were validated with experimental data obtained during measurements of textile evaporative resistance. The results obtained for the multilayer clothing during an energy-demanding activity (i.e. metabolic heat production of 300 W m(-2) and sweating of 240 g m(-3) h(-1)) show that a decrease in the emissivity of the outer surface (0.9 - 0.1), and an increase in the coefficient of water diffusion in the fibres of the inner layer (4 x 10(-16) - 4 x 10(-11)), induce an increase in the maximum skin temperature (of 4.5 degrees C and 6.8 degrees C, respectively). Moreover, the water trapped inside clothing is significantly increased by augmenting the fraction of fibre (0.07 - 0.4), the density of the fibre (910 - 7850 kg m(3)), the fibre affinity with water (i.e. regains of 0.07 - 0.3), and the coefficient of water diffusion in the fibres (4 x 10(-16) - 4 x 10(-11)). During the post-exercise phase (with metabolic heat production of 65 W m(-2) and perspiration of 9 g m(-3) h(-1)), the parameters affecting significantly the Water content of the inner layer are the fraction of fibre, its density, and its affinity with water. The proposed numerical approach allows the study of strategies to optimise heat/mass transport rates through materials surrounding the body (e.g. in clothing applications, automotive environments or work-place microclimates) in order to minimise thermal discomfort and/or problems of high water content (e.g. friction burns and/or growth of fungi and bacteria).