This model demonstrate buoyancy-induced air flow through a vertical shaft. On the right, there are two flow paths that are connected to a volume, which is kept at 20°C through a feedback controller, and to the ambient, which is at 0°C. The flow path on the very right consists of an orifice and two models that compute the pressure difference Δp between the bottom and top of the medium column using Δp=h ρ g, where h is the height of the medium column, ρ is the density of the medium column and g is the gravity constant.

The top model is parameterized to use the density from the ambient, whereas the bottom model is parameterized to use the density from the room volume, regardless of the flow direction. In the other flow path, the model sha is parameterized to use the density of the inflowing medium. Thus, these models can be thought of as a chimney to the left, and a roof with a leakage on the right. The chimney height starts 1.5 m below the roof, and ends 1.5 m above the roof.

The flow boundary condition of the model boundary is such that at the start of the simulation, air flows from boundary to roo until t=600 seconds. Then, the flow rate is set to zero until t=1800 seconds. Since the shaft sha is filled with 20°C air, there is a circulation in the clock-wise direction; up the shaft, and down the other flow path. Next, until t=2400 seconds, air is extracted from the volume roo, and then the flow rate of boundary is set to zero. Since the shaft sha is now filed with air at 0°C, there is a counter clock-wise flow; down the shaft, and up the other flow path.




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