Radiant heat transfer network in the simulated protective clothing system under high heat flux

A radiant network model was developed for design of the protective clothing system against solar and infrared radiative heat flux. A one-dimensional model was employed in the present study, because the aim of this study was to obtain precise temperature distribution through the system with use of a rather simple geometry. The model consists of a hot plate simulating the skin, layered underwear, an air gap of 8 mm thick, and a protective clothing layer. In the present study, several protective clothing materials made of para-polyamide fibre were used. Materials were identical, but had different colours. A series of experiments simulating the human wearing clothes has also been performed. One of the peculiar observations in the present experiment was that temperature on the protective clothing surface exposed to the radiation was often lower than the one on the inside of the outer fabric facing to the layered underwear; that is, the highest temperature arises inside the clothing and not on the clothing surface itself. Through an analytical solution of the heat conduction in the clothing with consideration of radiation heat transfer, it has been indicated that the point of the highest temperature appears in a depth about 0.3 mm from the surface in case of the IR heat flux, while 0.2 mm in case of the solar. This small but noticeable difference in the depth of the highest temperature between the two radiation types is due to the difference in the wavelength of the radiation. The position of the highest temperature has been revealed to be dependent upon properties of the material, the wavelength of the radiation and the heat transfer coefficient from the surface to the environment.