Journal of Applied Physiology, Vol 68, Issue 3 1275-1281, Copyright © 1990 by American Physiological Society
Convective heat transfer measured directly with a heat flux sensor
U. Danielsson
Department of Human Studies, National Defence Research Establishment, Stockholm, Sweden.
A heat flux disk has been developed that directly measures the convective
heat transfer in W/m2. When the sensor is calibrated on an aluminum
cylinder, the calibration constant obtained is greatest in still air. As
air movement increases, the calibration constant is reduced with increasing
convective heat transfer coefficient, 0.5%.W-1.m2.K. The influence of wind
on the calibration value is greatly reduced when the sensor is attached to
a surface with lower thermal conductivity. The local convective heat
transfer coefficient (hc) of the human body was measured. The leg acts in a
manner similar to that of a cylinder, with the highest hc value at the
front facing the wind and the lowest approximately 90 degrees from the
wind, and in the wake a value is obtained that is close to the average hc
value of the leg. When hc is measured at several angles and positions all
over the body, the results indicate that the body acts approximately as a
cylinder with a hc value related to the wind speed as hc = 8.6.v0.6
W.m-2.K-1, where v is velocity.
