On buoyancy-driven natural ventilation of a room with a heated floor

The natural ventilation of a room, both with a heated floor and connected t o a cold exterior through two openings, is investigated by combining quanti tative models with analogue laboratory experiments. The heated floor genera tes an areal source of buoyancy while the openings allow displacement venti lation to operate. When combined, these produce a steady state in which the air in the room is well-mixed, and the heat provided by the floor equals t he heat lost by displacement. We develop a quantitative model describing th is process, in which the advective heat transfer through the openings is ba lanced with the heat flux supplied at the floor. This model is successfully tested with observations from small-scale analogue laboratory experiments. We compare our results with the steady-state flow associated with a point source of buoyancy: for a given applied heat flux, an areal source produces heated air of lower temperature but a greater volume flux of air circulate s through the room. We generalize the model to account for the effects of ( i) a cooled roof as well as a heated floor, and (ii) an external wind or te mperature gradient. In the former case, the direction of the flow through t he openings depends on the temperature of the exterior air relative to an a veraged roof and floor temperature. In the latter case, the flow is either buoyancy dominated or wind dominated depending on the strength of the press ure associated with the wind. Furthermore, there is an intermediate multipl e-solution regime in which either flow regime may develop.