Theoretical analysis of the effects of human movement on the combined free-forced convection

Abstract

The airflow pattern close to a moving human is proved to be a combined free-forced convection due to the temperature difference between the moving human and the environment. In this paper, theoretical analysis was conducted to study the effects of human movement on the mixed convective heat transfer, expressed by Nusselt, Reynolds and Grashof numbers. The correlations of these non-dimensional numbers for each segment of the human have been established. It can be demonstrated that the increasing values of the Reynolds (forced convection) and Grashof (natural convection) numbers take a positive effect on the total rate of convective heat transfer, and the proportions of the forced and natural convection are on the same level. The heat transfer of the mixed convection is affected by the specific geometry characteristic of the different body segments. For the windward and leeward body segments, the heat transfer of mixed convection is more obvious during the human movement than other segments, while the heat transfer of mixed convection for the upper limbs by the body sides are much less obvious. In addition, a detailed information of the flow field around the moving body can be speculated from the correlation equations of the mixed convection for 18 body segments.