Experimental study of the interaction between thermal plumes and human breathing in an undisturbed indoor environment

Abstract

This study characterized the interaction between human thermal plume and breathing air flow while people are sitting in a quiescent indoor environment. A sitting breathing thermal manikin was developed to mimic a real human, and data from real human subjects was collected to verify the breathing thermal manikin. In this study the velocity and temperature were measured in front of and above the breathing thermal manikin with and without breathing. In addition, the breathing modes through mouth and nose were studied to investigate the influence of breathing mode on the development of thermal plume, respectively. The ambient temperature was set at 23 ± 0.5 °C, and the surface temperature of manikin varied between 33–34 °C. Without breathing, a maximum value of 0.19 m/s was reached at around 35 cm height above the head which was similar with the mouth-breathing case (0.19 m/s) and higher than the nose breathing case (0.17 m/s). However, the two breathing mode would mitigate the thermal gradient and lower the maximum velocity and had little influence on the height of maximum velocity. Above the manikin's head, non-breathing thermal manikin can produce very similar velocity distribution compared to the breathing modes. But the velocity above the head in the non-breathing case reported the highest maximum value and developed faster to reach the maximum velocity. Breathing through the nose had much more impact on thermal plumes around manikin than breathing through the mouth, even change the flow direction.