Simulation of the effect of wind on clothing by measurements and calculations

The conventional measuring methods of thermal resistance Rct and water vapour resistance Ret, do not give enough information about the function of winter clothing in different conditions. It has been suggested that sweating cylinder measurements could give more useful results especially in a windy environment. In this study two self-constructed cylinders were used, with diameters of 300 and 200 mm, both 500 mm in height. The cylinders were divided either into two 120° and two 60° sectors, which were controlled together or separately, or into one sector. The cylinder was placed in a wind-tunnel in the climatic chamber where ambient temperature (-15°C...+5°C) and wind velocity (1...8 m/s) were adjustable. Skin temperature (+35°C) and sweating level (0...120g/m²h) of the cylinder were controlled by a computer. Different types of multilayer winter clothing were studied by this method. The combinations used varied in materials, thickness (3 - 14 mm) and air permeability (7...177 l/m²s). The effect of wind on heat and mass flow has been described by the developed model. Increase of wind (1...8 m/s) decreased the total thermal resistance by 10...60 % in dry conditions and by 5...40 % in wet conditions. Mass transfer decreased by 0...40 % in cold. In the wind tunnel used the size of cylinder had no effect on measured apparatus constant. Neither was there any difference between the results measured by serial or parallel coupling of different heating sectors of cylinder. The differences in local insulation values are highest in the side sector of cylinder and the difference is the bigger the larger the cooling effect of air flow. The decreasing diameter of the cylinder increased the total thermal resistance of clothing. The effect of cylinder diameter was less than 5% with thick clothing and with thin clothing the effect was even 28%. The development of measuring method, the theory and the clothing models are under progress, but it is obvious that cylinder measurements are suitable especially in windy conditions