Large Eddy Simulation of Air Escape through a Hospital Isolation Room Single Hinged Doorway—Validation by Using Tracer Gases and Simulated Smoke Videos

Saarinen, Pekka E.; Kalliomäki, Petri; Tang, Julian W.; Koskela, Hannu

The most important result from this study is the volume of air migrating from the isolation room to the anteroom, in this single-hinged-door with/without manikin passage scenario. This quantity can be easily calculated by Eq (1) from a tracer gas measurement, or by integrating the amount of tracer gas 2 in room 1 in a simulation, see Eqs (2) and (3). A LES simulation provides more detailed information than measurements here in that it gives the AVM as a function of time. The upper plot in Fig 5 shows the AVM(t) curve given by LES, together with the total AVMs obtained from a series of tracer gas measurements. A very intense flow through the doorway can be seen at the very beginning of the door-opening phase. This is due to the piston effect of the moving door, which in the beginning reduces the air volume in the isolation room. This effect causes a rapid counter-flow through the gap between the door and its frame. In the CFD simulation a 2 cm high gap was left below the door to avoid convergence problems. Another occasion of intense flow occurs when the nurse passes through the doorway. This is also the moment when the two AVM curves ΔV 1!2 (t) and ΔV 2!1 (t) separate, because the air displaced by the nurse moves from room 1 to room 2. The separation between the curves equals the volume of the nurse, which in this simulation was 0.070 m 3 (generally, with a good precision, one litre per one kilogram of mass). Finally, the AVM curve of Then the total AVM would be 0.66 m 3 , which is almost exactly the same as the result by Kiel and Wilson. One should however note that the door used by Kiel and Wilson was an exterior door, not an interior door as in our case, and their data were rather scattered. In addition, Kiel and Wilson warn in their paper that their result for AVM due to door-pumping is not properly non-dimensionalized for the door size, and is therefore only valid for width W near 0.91 m used in their experiments. In our case W is 24% larger than this.