A new dynamic clothing model. Part 2: Parameters of the underclothing microclimate

Based on a new modeling, described in the first part of this paper, which t akes into account the pumping effect under garments, the various parameters characterising the confined air, and managing its dry and latent losses, a re determined. The mean temperature, calculated from heat exchanges with sk in (or underwear) and with the garment, progresses exponentially as a funct ion of the trapped time, until a limit. The mean humidity amount, determine d from the energy of total evaporation, from the air layer renewal rate and from the water vapour diffusion through the fabric, increases linearly. Us ing a movable thermal manikin, walking at various speeds, and with a combin ed effect with wind, the intrinsic air speed and convection coefficient are defined. The intrinsic air speed combines the effects of external air and body motions. The intrinsic convection coefficient is a linear function of the square root of the inner air speed. The relations expressing the trappe d rime are obtained, for thin and thick garments, by comparison between thi s new dynamic model and the model built by Lotens and Havenith (1991)which predicts the effect of posture, motion and wind on the clothing insulation. The evaluation of the amount of heat and mass transferred by pumping effec t requires the knowledge of all these parameters. (C) 2000 Editions scienti fiques et medicales Elsevier SAS.