# Practical Methodology for a Three-Dimensional-Printed Hybrid Desalination System
## 3 Results  
### CFD Simulations  
Two-dimensional simulations of velocity profiles were carried out for the proposed geometries across a range of flow rates, as detailed in Table 2. These simulations evaluated different initial flow rates, considering the operational limits of the pump. The goal was to determine the optimal range of velocities that the pump could sustain under realistic operating conditions, ensuring effective performance while minimizing potential flow limitations. These results provide valuable insights into the hydrodynamic behavior of the system, helping to refine the design parameters for improved reactor efficiency. The following boundary conditions were set for modeling the geometries:  
* 2D simulation;
* The fluid used in the simulation was pure water at 20 \({}^{\circ}\)C;
* Single-phase flow;
* Laminar flow;
* Steady-state condition;
* Incompressible fluid;
* Isotropic physical properties;
* No-slip condition at the walls;
* Outlet pressure set to 1 atm;
* Gravitational effects included;
* Hydrostatic pressure compensation condition applied. Figure 5 shows the velocity profile simulations for the first geometry (geometry 1) at different initial flow rates. In Figure 5a, with a flow rate of 10 mL/min, the flow is evenly distributed throughout the reactor. However, as the flow rate increases from 20 mL/min to 80 mL/min (Figure 5b-h), the uniformity of the flow diminishes. Higher velocities, such as those in Figure 5b (20 mL/min) and Figure 5c (30 mL/min), lead to areas of higher speed near the inlet and outlet, with slower regions forming in the center of the reactor. This pattern becomes more pronounced at flow rates of 40 mL/min to 80 mL/min, where irregular flow patterns are shown. The highest velocities consistently appear at the inlet and outlet, which can result in reduced mass and ion transfer efficiency. These findings suggest that while geometry 1 performs well at lower flow rates, its efficiency decreases as flow rates increase, highlighting the need to consider these factors in the design and operation of electrochemical reactors. \begin{table}
\begin{tabular}{c c c} \hline
**Simulation** & **Flow Rate (mL/min)** & **Flow Velocity (m/s)** \\ \hline (a) & 10 & 0.023 \\ (b) & 20 & 0.047 \\ (c) & 30 & 0.07 \\ (d) & 40 & 0.094 \\ (e) & 50 & 0.117 \\ (f) & 60 & 0.141 \\ (g) & 70 & 0.165 \\ (h) & 80 & 0.188 \\ \hline \end{tabular}
\end{table} 
Table 2: Velocity conditions for the evaluation of the proposed geometries. Figure 5: Velocity profile simulations of geometry 1 at different initial flow rates: (**a**) 10 mL/min, (**b**) 20 mL/min, (**c**) 30 mL/min, (**d**) 40 mL/min, (**e**) 50 mL/min, (**f**) 60 mL/min, (**g**) 70 mL/min, and (**h**) 80 mL/min. Figure 6 presents the velocity profile simulations for the second geometry (geometry 2) at several initial flow rates. This geometry has distinctive curved inlets and outlets, specifically designed to provide greater fluid inlet flexibility. The flow appears relatively uniform at a low flow rate of 10 mL/min (Figure 6a), with the highest velocities concentrated near the curved inlets and outlets. As the flow rate increases (Figure 6b-h), the uniformity of the flow is reduced. Starting from 20 mL/min (Figure 6b) and 30 mL/min (Figure 6c), higher velocity zones begin to form near the inlets and outlets, while slower regions develop in the reactor's center. This pattern intensifies at higher flow rates, as seen in Figure 6d-h, where irregular flow patterns emerge. In all cases, the highest velocities are observed at the inlets and outlets, as expected from the design. However, as flow rates increase, the flow distribution becomes less uniform, potentially impacting mass and charge transfer within the reactor. The CFD simulations indicated distinct flow behaviors for the two geometries evaluated. Geometry 1 exhibited a more uniform flow distribution at lower velocities, and as the flow rate increased, stagnation zones were reduced. However, geometry 1 consistently reached lower velocities compared to geometry 2.