The effective thermal resistance of permeable textile ensemble in windy environment

Abstract The dynamic resistance is one of the most important physical parameters to determine the clothing thermal comfort in actual-used conditions. Although it can be measured in a climate chamber using a thermal manikin, it is still difficult to predict dynamic resistance of textile ensemble by existing general method. In this study, a simplified model, which based on an analogy between heat flux and electric circuit, was developed to estimate the dynamic resistance of textile ensemble. The conductive (solid-phase) resistance of fibers and convective (gas-phase) resistance of air in the textile ensemble were considered simultaneously by the present model. A series of experiments were carried out in a climate chamber to study the relationship between the dynamic resistance, material structure, air permeability, wind velocity and ambient temperature. The results suggested that the dynamic resistance was equivalent to static resistance for textile ensembles with sufficient contact between fibers or textiles. However, for the textile ensemble with insufficient contact, the dynamic and convection resistance decreased with higher material permeability when stronger external wind was applied. In addition, the static resistance was observed to increase when textile was subjected to the lower ambient temperature and the dynamic resistance of low permeable textiles also increased, indicating the ambient temperature to be a dominant factor affecting the clothing thermal comfort. Then using the air permeability and static resistance tested in no windy condition, convective and dynamic resistance can be predicted in different conditions. The results can help to choose the most suitable windproof or permeable textile ensembles for the required thermal property in different conditions.