Impact of human body shape on forced convection heat transfer

Predicting human thermal comfort and safety requires quantitative knowledge of the convective heat transfer between the body and its surrounding. So far, convective heat transfer coefficient correlations have been based only upon measurements or simulations of the average body shape of an adult. To address this knowledge gap, here we quantify the impact of adult human body shape on forced convection. To do this, we generated fifty three-dimensional human body meshes covering 1st to 99th percentile variation in height and body mass index (BMI) of the USA adult population. We developed a coupled turbulent flow and convective heat transfer simulation and benchmarked it in the 0.5 to 2.5 m·s^-1 air speed range against prior literature. We computed the overall heat transfer coefficients, h_overall, for the manikins for representative airflow with 2 m·s^-1 uniform speed and 5% turbulence intensity. We found that h_overall varied only between 19.9 and 23.2 W·m^-2 K^-1. Within this small range, the height of the manikins had negligible impact while an increase in the BMI led to a nearly linear decrease of the h_overall. Evaluation of the local coefficients revealed that those also nearly linearly decreased with BMI, which correlated to an inversely proportional local area (i.e., cross-sectional dimension) increase. Since even the most considerable difference that exists between 1st and 99th percentile BMI manikins is less than 15% of h_overall of the average manikin, it can be concluded that the impact of the human body shape on the convective heat transfer is minor.