Skin Temperature, Heat Loss And Thermal Resistance Of The Cheek During Exposure To Cold Winds
Michel B. Ducharme, Defence Research and Development Canada, Toronto, ON, Canada; and D. Brajkovic, R. Osczevski, and P. Tikuisis
Skin heat loss and tissue thermal resistance are essential variables for modeling heat transfer from the face in cold winds and for the development of a reliable wind chill index. The objective of the present study was to measure skin temperatures (Tsk) and heat losses (Hsk), and to calculate, using the inside surface cheek temperature, the tissue thermal resistance (R) of the cheek during exposures to cold winds. Twelve subjects (6 males and 6 females) were exposed to four 90 min tests where the wind intensity changed from 2 to 5 to 8 m/s at 30 min intervals. The tests were conducted at 10, 10 (wet), 0, and -10°C. In the wet test at 10°C, a fine mist of water was spayed to the face of the subject every 15 sec. During the tests, the subjects were dressed for thermal comfort, walked on a level treadmill at a speed of 4.8km/h and were facing the wind with their face fully exposed. At 10°C, the last 10 min average (± SD) when steady-state was achieved in most cases for Tsk, Hsk and R varied from 23.0 ± 2.8°C, 280 ± 55W/m2, and 0.045 ± 0.013°Cm2/W at 2m/s to 18.3 ± 2.6°C, 329 ± 63W/m2, and 0.049 ± 0.017°Cm2/W at 8m/s. At 0°C, the last 10 min average for Tsk, Hsk and R varied from 17.7 ± 2.2°C, 370 ± 66W/m2, and 0.048 ± 0.014W/m2 at 2m/s to 11.9 ± 2.1°C, 467 ± 120W/m2, and 0.049 ± 0.016°Cm2/W at 8m/s. At -10°C, the last 10 min average for Tsk, Hsk and R varied from 13.4 ± 2.4°C, 485 ± 72W/m2, and 0.044 ± 0.012W/m2 at 2m/s to 9.3 ± 2.5°C, 963 ± 229W/m2, and 0.027 ± 0.008°Cm2/W at 8m/s. The wet exposure at 10°C decreased Tsk on average by 5°C and increased Hsk by 100W/m2 as compared to the dry exposure. The decrease of R at -10°C (5 and 8m/s) was attributed to cold-induced vasodilatation (CIVD). It was concluded that the thermal resistance of the cheek tissue averages 0.051°Cm2/W and is not dependent on ambient temperature and wind intensity in the absence of CIVD. When CIVD is present, R is inversely related to the wind intensity.
Poster Session 1, Poster Session: Human Biometeorology
Monday, 28 October 2002, 1:00 PM-2:00 PM
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