4567 -- A Water Tank Experiment on the Influence of Occupants’ Natural Convection on Ventilation Efficiency PDF

In displacement room airflow, a high efficiency is attained, encouraging thermal stratification in a room. In the present study, the influence of the natural convection around an occupant’s body on this stratification was examined using a water tank model of a small office. The forced ventilation in the tank was simulated, equalizing the Reynolds numbers of the office and the tank. The natural convection in the tank was simulated by heated cylindrical models of the same Grashof number as a real body. In ceiling-to-floor flow, the thermal stratification disappeared at an air change rate of less than 3 ach. In floorto- ceiling displacement flow, it held until the air change rate exceeded 5 ach. Even as the thermal stratification became unclear, natural convection transported a large part of the occupant’s heat directly to the ceiling return air inlet in the floor supply outlet-to-ceiling inlet and low-sidewall supply outlet-to-ceiling inlet configurations.

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