This paper deals with methods for control of the free convection flow around the human body, the aim being to improve the quality of the inhaled air for occupants at workstations with personalized ventilation (PV). Two methods of control were developed and explored: passive - blocking the free convection development by modifications in desk design, and active - by local suction below the desk. The effectiveness of the two methods for enhancing the performance of PV was studied when applied separately and combined, and was compared with the reference case of PV alone. The experiments were performed in a full-scale test room with background mixing ventilation. A thermal manikin with realistic free convection flow was used. The PV supplied air from front/above towards the face. All measurements were performed under isothermal conditions at 20 °C (68 oF) and 26 °C (78.8 oF). The air in the test room was mixed with tracer gas, while personalized air was free of it. Tracer gas concentration measurements were used to identify the effect of controlling the free convection flow on inhaled air quality. The use of both methods improved the performance of PV and made it possible to provide more than 90% of clean air for inhalation at a substantially reduced PV supply flow rate.

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