Distribution of Evaporation Rate on Human Body Surface

Relative humidity (R. H), vapour pressure (Psk) and evaporation rate (Esk) of the human skin surface were measured at 29 points by an evaporimeter at 25 degrees C, 28 degrees C, 31 degrees C, 34 degrees C and 37 degrees C of air temperature (Ta), with 35 +/- 10 % R. H and air velocity of less than 0.2 m/s. The skin temperatures and the body weight loss were also measured by thermography and electronic balance. Ten healthy female subjects aged 22-34 years, wearing brassiere and shorts, took a supine and a prone posture during experiment. Comparisons of the obtained Esk with the previous results of other studies showed that there were no definite differences among the measuring methods of Esk, while it is ascertained that the calibration of the results to some standard values such as weight loss were more important to get accurate values of Esk. Distribution patterns of Esk were almost the same in the insensible zone but they remarkably changed in the sweating zone. According to the regression analysis of Esk and Ta, 29 regions were classified into the following 9 groups which showed similar values and changes of Esk with the air temperature: 1) face, 2) front upper trunk, 3) back upper trunk, 4) front lower trunk, 5) back lower trunk, 6) arm, 7) leg, 8) hand and foot and 9) palm, sole and axilla. These results were discussed in relation to the contributing factors such as the number and the capacity of the sweat gland, the regional skin temperature and the pressure-sweat response and also in relation to the skin wettedness.