Impact of facially applied air movement on the development of the thermal plume above a sitting occupant

In the future the implementation of low power office equipment in practice will make thermal plumes generated by occupants one of the dominant flows affecting the air distribution in spaces. Advanced air distribution methods, such as personalized ventilation, are expected to become widely implemented in practice. In this study the impact of locally applied airflow on the thermal plume generated by a sitting human body was investigated. The experiment was performed in a climate chamber with upward piston flow. A thermal manikin was sitting on a computer chair behind a table. The air speed and temperature were measured across the plume 0.7 m above the manikin head when an airflow of 10 l/s was supplied first against the face of the manikin and then upward from the front edge of the desk. The use of the flow, against the face or upward tangentially to the chest, disturbed significantly the free convection boundary layer enveloping the body and caused scattering in the measured values of air speed and temperature excess in the plume. In comparison with the case without airflow, the integral characteristics including volume flux, momentum flux, buoyancy force density and enthalpy flux were greater when the flow was supplied upward tangentially to the chest and lower when it was supplied against the face.