Experimental Study on Thermophysiological Response of Clothed Subjects Exposed to Thermal Transients – Sweating and Evaporation Process –

Abstract

Laboratory experiments are conducted with the use of clothed subjects in order to clarify the effects of moisture movement and accumulation in clothing on the body temperature regulation system. The sweating and evaporation process is focused on as a typical situation that people experience under a hot climate. The thermal transients a subject is exposed to are comprised of three steps as follows: Step 1: 25[°C], RH 50%, for 30 minutes; Step 2: 35[°C], RH 90%, for 30 minutes; and Step 3: 25[°C], RH 50%, for 60 minutes. Not only the skin temperatures but also the clothing temperatures are measured during the process, and the influence of the moisture on the skin temperature is investigated based on measured results. Our conclusions are as follows.For the sweating processa) The clothing temperatures show two sharp rises explained by moisture absorption into the clothing from the ambient air and the skin.b) The rise in clothing temperature seems to affect the skin temperature. In order to explain the variation in the clothing and the skin temperatures, it might be necessary to take into account the contact between the skin and the clothing.For the evaporation processa) The unclothed skin temperatures show a sharp decrease 5-10 minutes after moving to the low temperature environment and, after that, the temperatures remain almost constant.b) The clothing and the clothed skin temperatures first decrease and then increase. The time when they assume the minimum values is closely related to the amount of moisture accumulated at the point of the body. In most experiments, it is earliest at the shoulder.c) The clothed skin temperatures assume their minimum values much later than the unclothed skin temperatures. Not only the thermal and the hygric resistance of the clothing but also the moisture accumulation in the clothing is responsible for this fact.