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

Figure 67. Airflow Patterns for the Buoyancy Case: Full Model with Stacks Open7.2 Wind-Driven Ventilation ResultsThe experiments on the physical and CFD models were carried out for a range of wind speeds,both with and without the use of the heaters for the internal loads. The wind-only cases arepresented first for the full-model configuration with either all of the stacks open or all closed.The inlet velocities and outlet velocities were measured and airflow balance calculated.7.2.1 Wind-Only CaseConducting the wind-only cases before the addition of internal heat loads assisted in theunderstanding the air velocities caused by wind alone. Experiments were carried out using avariety of fan speeds, simulating external wind conditions. The stacks were set to either all openor all closed for each of the fan speeds to determine how much wind exited through the stackvents when they were open.The focus of the wind-only experiments was determining the inlet velocity at the windows on thesouth façade and the resulting outlet velocities on the north façade and at the stacks for the stacksopen scenarios. Using the wind device described in Chapter 6, the model was evaluated at fivedifferent wind speeds. The inlet velocities were recorded at 5 m/s at fan setting 3, 4 m/s at fansetting 2, and 3 m/s at fan setting one. Further experiments were carried out at lower fan settingsusing a Variac® that reduced the voltage provided to the fans. Measurements were recorded attwo additional points, at fan setting 1 with the Variac® at 83% and at fan setting 1 and theVariac ® set at 57%. This provided air velocities of 2 m/s and 1 m/s respectively. The inletvelocities were uniform across the south façade of the model as measured at the face of thewindow, and at all of the inlet windows. The measurements between windows deviated by±0.1m/s, which was the measurement error of the hot-wire anemometer used. The airflowbalance was determined by calculating the inflow volume of air, minus the outflow volume ofair, divided by the inflow volume of air. The maximum percentage error in the airflow balance139