Analytical clothing model for sensible heat transfer considering spatial heterogeneity

Existing clothing models assume spatial homogeneity of the enclosed air layer between skin and fabric, which contradicts real-life scenarios. Furthermore, depending on the thickness of enclosed air layer and the temperature difference between skin and fabric, natural convection may occur but it is often neglected in the theoretical models. In this study, we have developed a theoretical model that considers the spatial heterogeneity of enclosed air layer and natural convection. It computes the sensible heat transfer (conduction, radiation and natural convection) in the heterogeneous enclosed and boundary air layers. The heat transfer in the clothing layer is calculated based on the thermal resistance of the fabric. The model presented in this paper is systematically validated for natural convection and spatial heterogeneity using a thermal cylinder and a thermal manikin with increasing level of spatial complexity. The validation of the model was performed for a wide range of temperatures (-10 degrees C to 26 degrees C), enclosed air layer thicknesses (homogeneous and heterogeneous), and ambient air speeds (0.2 m/s, 1 m/s) and demonstrated a good agreement between predicted and measured heat flux with an average error of 3.7% and 9.3% for homogeneous and heterogeneous enclosed air layers, respectively.