Impact of breathing on the thermal plume above a human body

The characteristics of the thermal plume above a human body should be well-defined in order to properly design the indoor environment and allow correct simulation of the indoor conditions by CFD or experimentally. The objective of the presented study was to investigate the influence of breathing on the characteristics of the thermal plume generated by a sitting person.

The experiment was performed in a climate chamber with upward piston flow. Air temperature was 23°C, vertical temperature gradient was approx. 0.07 K/m and velocity was lower than 0.05 m/s. Radiant temperature asymmetry was close to 0°C. A thermal manikin with female body shape equipped with an artificial lung was used to simulate the dry heat loss and breathing process of a sitting occupant.

Three cases were examined: non-breathing, exhalation through nose, and exhalation through mouth. Measurements of the air temperature and speed in the plume cross-section 0.7 m above the manikin head were performed. Exhalation through the mouth affects the characteristics of the thermal plume 0.7 m above the manikin head, while exhalation through the nose has only small impact.

Air velocity and temperature excess distributions in the plume generated by the manikin exhaling through the nose are comparable to the distributions over the non-breathing manikin. Exhalation through the mouth causes wider plume cross-section and increases the volume flux, momentum flux, buoyancy force density and enthalpy flux compared to the non-breathing case.