## 2 Materials and Methods
### Solution Domain Model and Validation  
A commercially available air cleaner was selected for numerical modelling. Then, it was modelled inside a room which was appropriate with the AHAM standard [18]. The dimensions and the location of the selected air cleaner and the room are given in Figure 1.  
Two different positions of the air cleaner in the room were examined: the device positioned 0.5 m away from the wall (position 1), as shown in Figure 1, and the device positioned in the middle of the room (position 2).  
The purified air inlet velocity, the turbulent intensity, and the turbulent viscosity ratio were specified at the blowing area. The zero-pressure condition was applied to the suction outlet area of the ACD. To all walls, including door, window, room boundaries, and the device walls, the no-slip condition was applied. Constant temperature, 295 K, was defined at the room boundaries. Since the ACD device components, such as the electric motor, produce some heat, the temperature at the ACD surfaces was set to 300 K.  
For mesh independence analysis, the mean air age and velocity values of three distinct meshes with differing node counts were compared. Figure 2 displays the air velocity values in the center of the room obtained using various meshes. After the calculations were conducted  
Figure 1: Schematics of the modelled room and air cleaning device.  
using this mesh structure and the 1.8 \(\times\) 10\({}^{6}\) node number, it was seen that the findings remained unchanged. Therefore, this mesh number was used for all further calculations.  
Numerical results were validated by measuring the air velocity in a room with the exact dimensions given in Figure 1. A TSI Q-Trak measuring device with a TSI 966 velocity probe was used for these measurements. The probe resolution and accuracy were 0.01 m/s and \(\pm\)0.05 m/s, respectively. The air velocity was measured at 12 different points to compare the numerical results with measurements; the coordinates of these points, as well as the measured and computed velocity values, are given in Table 1. The locations of these points are given based on the origin of the coordinate system shown in Figure 1.  
A comparison of the measurement results and the numerical prediction results for the velocity values is given in Table 1. The relative difference between the calculated and the measured velocity values was less than 5% at all points except for the location of P6. Considering the very low velocities in the room and the accuracy of the probe used for measurement, it was concluded that the numerical results were in good agreement with the experimental results.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Points** & **X (m)** & **Y (m)** & **Z (m)** & \begin{tabular}{c} **Measured** \\ **Velocity (m/s)** \\ \end{tabular} & \
\begin{tabular}{c} **Predicted** \\ **Velocity (m/s)** \\ \end{tabular} &
\begin{tabular}{c} **Diff.** \\ **\%** \\ \end{tabular} \\ \hline P1 & 1.875 & 1.5 & 1.0 & 0.06 & 0.059 & 1.7 \\ \hline P2 & 0.9375 & 1.5 & 1.0 & 1.00 & 0.990 & 1.0 \\ \hline P3 & 2.8125 & 1.5 & 1.0 & 0.05 & 0.048 & 4.0 \\ \hline P4 & 0.9375 & 2.25 & 1.0 & 0.06 & 0.059 & 1.7 \\ \hline P5 & 1.875 & 2.25 & 1.0 & 0.06 & 0.061 & 1.7 \\ \hline P6 & 2.8125 & 2.25 & 1.0 & 0.08 & 0.075 & 6.3 \\ \hline P7 & 1.875 & 1.5 & 0.5 & 0.11 & 0.105 & 4.5 \\ \hline P8 & 0.9375 & 1.5 & 0.5 & 0.09 & 0.090 & 0 \\ \hline P9 & 2.8125 & 1.5 & 0.5 & 0.05 & 0.052 & 4 \\ \hline P10 & 0.9375 & 2.25 & 0.5 & 0.08 & 0.078 & 2.5 \\ \hline P11 & 1.875 & 2.25 & 0.5 & 0.07 & 0.067 & 4.3 \\ \hline P12 & 2.8125 & 2.25 & 0.5 & 0.06 & 0.057 & 5.0 \\ \hline \hline \end{tabular} The origin of the coordinate system is given in Figure 1.  
\end{table}
Table 1: Air velocity comparison of experimental and numerical results.  
Figure 2: Variation of the velocity magnitude at the line placed in the center of the room.