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

modified to determine the impact of the effective area ratio of inlet to outlet areas on thetemperature and airflow. The ground floor south half-floor was used as the single heated zoneconnected to the atrium. This was the zone most readily isolated and provided the maximumheight differential between the inlet and outlet openings to drive the buoyancy-driven ventilation.This configuration, along with the location of the thermocouples used in measuring thetemperature variation throughout the single-zone model, is shown in Figure 38.One-inch thick insulation board was used to isolate the heated zone and atrium from the rest ofthe model. The insulation board was placed on the north side of the atrium and the connection ofthe south first floor to the atrium. The surface area of the modified model is 12 square meters.All surfaces have a layer of insulation board on the external surface in order to reduce the heatlosses to the ambient. Foil tape and duct tape were used at major junctions in order to provide aseal, such as to prevent uncontrolled infiltration, exfiltration, and heat loss. The overall heattransfer coefficient was calculated both by measured data and through calculations using materialdata properties. Thermocouples were located throughout the model; measuring horizontal andvertical temperature variation in both the heated zone and atrium. Airflow visualizationtechniques, using the smoke pencils, were incorporated into the experiment to understand theflow patterns and determine if they varied with the location of the windows.The CFD simulation of the single heated zone model kept the same geometry as the reduce-scalemodel construction. A large plate heater was located on the floor in the heated zone with aprescribed heat flux that was uniform over the plate surface. The ambient conditions for thecomputational model were derived from measured experimental data. The CFD model wasrefined in a second step by adding an additional heater plate on the ceiling to replicate theradiation heat transfer that was observed between the heaters on the floor and the ceiling in theexperimental case. All other surfaces were originally kept as adiabatic in the computationalmodel. In a third and final step, prescribed heat loss at key surfaces, particularly those in theatrium, were inserted into the CFD model to more accurately simulate the experimentalconditions.108