A theoretical and experimental study of the thermal insulation of clothing in windy conditions

In windy conditions, the thermal insulation of clothing can be considerably reduced by air penetration and changes in clothing geometry. In order to understand the problem, it is important to examine the mechanisms involved before selecting suitable clothing materials and using them in the construction of clothing which is effective in strong windy conditions. Most of the previous work reported on this topic analysed clothing assemblies which covered flat surfaces and this was considered either in theoretical[1] or experimental studies[2,3]. Yankelevich[4] showed that this approach is not adequate in view of the dynamic air pressure distribution which, for a flat surface differs from that at the surface of a cylinder of a human trunk or limb. Some work has been carried out experimentally[5,6] for simple cylindrical clothing systems. In theory, the existing model presented[7] was rather preliminary. The work described here uses a better performing system, and theoretical and experimental analyses. In such systems, the clothing assembly consists of two layers, an outer fabric and inner porous fibrous material. A limb or body is approximated to as an internally temperature-controlled hollow cylinder (see Figure 1). The theoretical solution obtained was compared with experimental results obtained in a wind tunnel when a number of different mechanisms involved were identified in wind-induced heat loss and in reduction of thermal insulation. © 1989, MCB UP Limited