CONVECTIVE HEAT-TRANSFER MEASURED DIRECTLY WITH A HEAT-FLUX SENSOR

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 (h(c)) of the human body was measured. The leg acts in a manner similar to that of a cylinder, with the highest h(c) value at the front facing the wind and the lowest ~90° from the wind, and in the wake a value is obtained that is close to the average h(c) value of the leg. When h(c) is measured at several angles and positions all over the body, the results indicate that the body acts approximately as a cylinder with an h(c) value related to the wind speed as h(c) = 8.6·v0.6 W·m-2·K-1, where v is velocity.