Natural convection around the human head

Area of Science:

• Thermodynamics
• Human Physiology
• Fluid Dynamics

Background:

• Understanding heat transfer from the human body is crucial for thermal comfort and safety.
• Body posture influences convective airflow and associated heat loss.
• Previous studies have not fully quantified posture-dependent heat loss from the head.

Purpose of the Study:

• To investigate the impact of body posture (erect vs. supine) on convective heat transfer around the human head.
• To quantify the differences in total heat loss from the head between erect and supine positions.

Main Methods:

• Utilized a schlieren optical system to visualize airflow patterns around the head.
• Employed surface calorimeters to measure local convective and radiative heat transfer.
• Calculated total heat loss based on local measurements for both body postures.

Main Results:

• The erect posture resulted in a thicker insulating layer of convecting air around the head compared to the supine position.
• Local heat transfer measurements correlated with the thickness of the convective boundary layer.
• Total heat loss from the head was 30% greater in the supine position than in the erect position.

Conclusions:

• Body posture significantly alters convective heat transfer from the human head.
• The supine position enhances heat loss from the head due to changes in airflow dynamics.
• These findings have implications for thermal regulation and environmental design.