Convective heat transfer from a nude body under calm conditions: assessment of the effects of walking with a thermal manikin
2012
Oliveira, A. Virgílio M. | Gaspar, Adélio R. | Francisco, Sara C. | Quintela, Divo A.
The present experimental work is dedicated to the analysis of the effect of walking on the thermal insulation of the air layer (I a ) and on the convective heat transfer coefficients (h conv ) of the human body. Beyond the standing static posture, three step rates were considered: 20, 30 and 45 steps/min. This corresponds to walking speeds of approximately 0.23, 0.34 and 0.51 m/s, respectively. The experiments took place in a climate chamber with an articulated thermal manikin with 16 independent parts. The indoor environment was controlled through the inner wall temperatures since the objective of the tests was restricted to the influence of the walking movements under calm conditions. Five set points were selected: 10, 15, 20, 25 and 30°C, and the operative temperature within the test chamber varied between 11.9 and 29.6°C. The highest and lowest I a values obtained were equal to 0.87 and 0.71 clo, respectively, and the reduction in insulation due to walking ranged between 9.8 and 11.5%. The convective coefficients (h conv ) for the whole body and for the different body segments were also determined for each step rate. In the case of the whole body, for the standing static reference posture, the mean value of h conv was equal to 3.3 W/m2°C and a correlation [Nu = Nu(Gr)] for natural convection is also presented in good agreement with previous results. For the other postures, the values of h conv were equal to 3.7, 3.9 and 4.2 W/m2°C, respectively for 20, 30 and 45 steps/min.
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