Measurement of solar radiation absorptance of different clothing fabric for outdoor thermal comfort study

Absorptance of clothing for short-wave radiation is an important factor in thermal comfort assessment based on the human body heat budget outdoor. Many researchers have adopted value of 0.7 prescribed in VDI 3787 as the solar absorptance of human body. However, the solar absorptance of human body should depend on material and color of clothing fabric substantially. The objective of this research is to identify solar absorptances of ten different clothing fabrics combining of two materials (100% cotton, 65% polyester/35% cotton) and five colors (black, white, gray, red and blue). The measurement was carried out in October and November, 2007. By using the pyranometers, total solar radiation, reflected solar radiation by the target fabric and surrounding ground surface, and transmitted solar radiation through the target fabric were measured. In a calculation of the solar absorptance, the reflected component from outside of the target fabric was separated from the measured reflected radiation by taking into consideration a configuration factor between the measuring sensor and the fabric. The following findings were obtained through the experiment. The identified solar absorptances of 100% cotton fabric were 0.61 for black, 0.17 for white, 0.36 for gray, 0.47 for red and 0.57 for blue. The identified solar absorptances of 65% polyester/35% cotton fabric were 0.61 for black, 0.17 for white, 0.35 for gray, 0.44 for red and 0.49 for blue. The solar absorptance of clothing fabric does not depend on direct and diffuse solar radiations. The solar absorptance of clothing fabric depends on material and color of fabrics.<br>