## 2 Materials and Methods

Table 2: Juvataposition of the geometric parameters of the flow channels on the lab bench. flow channels used for experimental investigations, and sampling lines are also included. Table 3 presents a set of parameters the values of which were estimated empirically. The air-water pneumatic nozzle (see Table 11) generated water droplets in a wide size spectrum up to \(\sim\)200 \(\upmu\)m. The Droplet Size Analyzer (\(DSA\), see Appendix D, Table 14) was employed for the \(DSD\) measurements of the large droplets (with diameter > 40 \(\upmu\)m). These data were collected and further applied to perform a comparative analysis as presented in Section 3. The droplet size that was preferred was limited to 20 \(\upmu\)m. In this case, the \(DSA\) was obtained by applying a product of Topas, which was Aerosol Particle Size Spectrometer LAP 332 (\(APSS\)) (see Appendix D, Table 14). This device produced a relatively low underpressure and was employed to aspirate the droplets from the core of the flow, as presented in the scheme of the laboratory stand (Figure 1, 6.). To prevent larger droplets from being aspirated into the flow, the straight channel (\(SCh_{1}\)) required tilting, which was intentional due to limitations in \(d_{d}\). Adding a gravitational component to the equation of droplet motion was realized by sloping the channel by 20\({}^{\circ}\). As the diameter of the droplet increases, the mass force acting on it increases. The large droplets undergo a gravitational separation at the very beginning. Hence, they were naturally excluded from the cloud of droplets being sucked into the sloped channel. This approach allows for a correlation to be established between the turbulence intensity _Tu_ (_Tu_--_a_ ratio of the velocity fluctuations to the mean velocity of the flow) and the gas flow velocity measured at different lengths of the sloped channel. In addition, the outcomes of the \((PIV)\) (see Appendix D, Table 13) measurements validated the \(DSD\) data, which was obtained with \(APSS\). In the view of the flow registered by employing \(PIV\), the small droplets were mostly present in the core of the flow, as desired. Performing multiple background experiments was necessary to determine an adequate procedure of measurements taken. Figure 1 depicts the view of the lab bench. A fan (Figure 1, 7.) was used to draw in the droplets with the desired sizes from the cloud of droplets generated by the air-water nozzle (Figure 1, 3.). The fan was used to provide the air-droplet flow through all measuring channels. PIV (Particle Image Velocimetry) is an optical and non-invasive method that was employed to ascertain the velocity fields of both the continuous and dispersed phases. Two velocity components of the mist flow can be identified by imaging the movement of droplets (or particles) using a laser that illuminates them in a plane. By a comparison of the outcomes of \(DSD\) measurements with respect to the geometrical and flow parameters existing, it was possible to determine the mechanisms supporting the separation of a given fraction of droplets. The geometric parameters and quantity of small droplets in the core of the flow were correlated using channel elbows. By these means, the impact of the inertia forces of the gas on the presence of small droplets in the main flow was ascertained. The empirical data gained and their further theoretical analysis constitute a source based on which it was possible to determine the mechanisms supporting the droplet deposition on the wall. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Unit** & **Value** \\ \hline \(\rho_{w}\) & \(\frac{\text{kg}}{\text{m}^{2}}\) & 999.7 \\ \(\delta_{bl}\) & \(\text{m}\) & \(19.6\cdot 10^{-3}\) \\ \(\left(\frac{d\theta}{dx}\right)_{max}\) & \(\frac{1}{\text{s}}\) & 4.8 \\ \(\kappa\) & – & 0.41 \\ \(\rho_{a}\) & \(\frac{\text{kg}}{\text{m}^{2}}\) & 2.36 \\ \(\mu_{a}\) & \(\text{Pa}\cdot\text{s}\) & \(1.85\cdot 10^{-5}\) \\ \(v_{a}\) & \(\frac{\text{m}^{2}}{\text{s}}\) & \(7.84\cdot 10^{-6}\) \\ \hline \hline \end{tabular}
\end{table}