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

was less than 12 percent. These values, along with the measured velocities for the wind-drivenflow experiments are presented for the stacks closed case in Table 35 and for the stacks opencase in Table 36. When the stacks were closed, the only location of outflow of air was at thenorthern façade. The inlet windows on the south façade were smaller in size than the outletwindows on the north façade. The inlet windows were 2 cm tall by 12 cm long, whereas theoutlet windows were 2 cm tall by 17 cm long. There were an equal number of windows on thenorth and south façades.Table 35. Average Inlet and Outlet Velocities for Wind-Driven Case: Stacks ClosedSetting 3 Setting 2 Setting 1 Setting 1-83% Setting 1-57%Window Inlet 5.1 m/s 4.0 m/s 2.9 m/s 2.0 m/s 1.0 m/sWindow Outlet 3.2 m/s 2.6 m/s 1.8 m/s 1.3 m/s 0.7 m/sAirflow Balance 10.6% 7.4% 11.6% 7.4% 0.2%Table 36. Average Inlet and Outlet Velocities for Wind-Driven Case: Stacks OpenSetting 3 Setting 2 Setting 1 Setting 1-83% Setting 1-57%Window Inlet 5.1 m/s 4.1 m/s 3.0 m/s 2.0 m/s 1.0 m/sWindow Outlet 2.8 m/s 2.3 m/s 1.7 m/s 1.1 m/s 0.6 m/sStack Outlet 3.1 m/s 2.2 m/s 1.9 m/s 1.0 m/s 0.5 m/sAirflow Balance 6.5% 6.6% 3.3% 9.1% 1.9%The air entered through all of the window openings on the south façade at the same velocity, andexited the north façade with uniform velocity. In the stacks open scenario, approximately 85percent of the air exited at the north façade and the remaining 15 percent of the air exited throughthe stack openings. This was consistent over the range of wind velocities used for the wind-onlycase.7.2.2 Combined Wind-Buoyancy Driven CaseThe addition of heaters to mimic the internal loads to the wind cases resulted in a combinedwind-buoyancy airflow. The heaters were left on at full strength, while the speed of the fans wasadjusted, from 5 m/s down to 0.5 m/s. Both temperature measurements and inlet and outletvelocity measurements were recorded and an airflow balance calculated.The wind speeds that were utilized in the wind-only cases were used in the combined windbuoyancycase. However, with these inlet velocities the wind-driving force dominated theairflow. So reduced fan speeds were used to achieve wind speeds at the inlet windows on thesouth façade of 2 m/s, 1 m/s, 0.7 m/s and 0.5 m/s. The measured inlet and outlet air velocitiesfor the stacks open case are presented in Table 37. As the inlet air velocity decreased, thepercentage of air exiting through the stacks increased. This is shown graphically in Figure 68,where the dashed lines represent the buoyancy case for reference. For the stacks closed case, allof the entering air from the south façade where the wind device is located exited throughwindows located on the north façade. When there is no wind present, under pure buoyancydrivenflow, a greater percentage of the outflow exits through the stacks. As the applied windspeed increases, the percentage of outflow that exits through the stacks decreases.140