Methodology for the Evaluation of Natural Ventilation in ... - Cham

natural-environment features, the associated changes of chemical and physical composition, andthe associated stresses in the immersed solids.A model with the same geometry and dimensions as the scaled physical model was created usingthe PHOENICS program. The surrounding conditions were made to simulate the test chamberconditions, including the dimensions, wall temperature and location within the chamber. As withthe scaled physical model, there are cutouts for the window and stack vent openings with thesame size as those elements in the physical model. The CFD model however did not usecolumns in the simulation, as in the scaled physical model the columns have a negligible effecton both the airflow patterns and temperature. A cross-section of the CFD model is shown inFigure 35.Figure 35. PHOENICS Scale Model GeometryThe CFD software was found to have limitations for use in simulations of the reduced scale airmodel. Surfaces such as walls and floors are considered adiabatic in CFD simulations. Therewas no easy way to simulate the thermal properties associated with heat loss through theenvelope or between floor constructions. The surfaces of the experimental case, the reducedscaleair model, were not adiabatic and had some amount of heat loss through the envelope.Results from the reduced scale air model with heat loss for each experiment provided data forcomparison with each corresponding CFD simulation with adiabatic walls. The strength of heatsource used in the reduced-scale air model were also described in the CFD model. Theprescribed heat sources in the CFD model were 283W each, to simulate the heaters in thephysical scaled model, and therefore the internal loads for the prototype building. The heatsource, sited in approximately the same location as in the scaled physical model, was distributedover the entire size of the aluminum plates. In the single zone model, heat loss through the wallswas modeled in the atrium portion, as is described in Section 6.5.1.1 Single Heated ZoneExperiments.101