Investigation of heat transfer and temperature distribution in outdoor human-clothing-environment systems with double-layered ensemble

The thermal behavior in a clothing microclimate is an important aspect related to thermal comfort. Situation-dependent analyses are required to understand the heat transfer of clothing; thus, the heat transfer and temperature distributions in a double-layered human-clothing-environment system in the presence of solar radiation are investigated as practical application in this study. A new heat transfer model modified from the previously proposed outdoor thermal model with single-layered clothing is developed. The new model integrates the radiative effects on clothing, the heat conduction within the air layer, and the heat convection on the outer surface of clothing. Radiation heat transfer is included as a source term for the clothing. Measurements of the temperature distributions are obtained under typical summer and winter atmospheric conditions with or without solar radiation to validate the model. A comparison confirms that the prediction model is valid. Subsequently, the effects of layered clothing are analyzed. Since insulation fundamentally influences the temperature distributions in the steady-state system, the temperatures at the boundary and air gap determine the slopes of the temperature distribution. Since the absorbed solar energy is more influential than the release of heat by conduction or even convection for clothing, the solar radiation and radiative properties are relatively dominant at the temperature distribution of clothing and consequently the entire system. Overall, the effects of solar radiation and the properties related to radiation are essential for evaluating the microclimate inside clothing. (C) 2017 Elsevier Ltd. All rights reserved.