# CFD Simulation of Dry Pressure Drop in a Cross-Flow Rotating Packed Bed
## 5 Conclusions  
In this work, a 3D CFD model is established to investigate the dry pressure drop in the four zones of the cross-flow RPB, namely the cavity zone A, packing zone, cavity zone B and outlet zone. It was found that there is a good agreement between simulated and experimental results. Then, the effects of rotating speed and gas flow rate on dry pressure drop are investigated by the proposed model. In the cavity zone A, the static pressure increases with increasing rotating speed and decreasing gas flow rate, while the dynamic pressure drop decreases with increasing rotating speed and decreasing gas flow rate. In the packing zone, the static pressure increases slightly with increasing rotating speed and gas flow rate, while the dynamic pressure drop decreases with increasing rotating speed and decreasing gas flow rate. In the cavity zone B, the static pressure increases, while the dynamic pressure drop decreases with the decrease of rotating speed and gas flow rate. In the outlet zone, both static and dynamic pressure drop remain constant with increasing rotating speed. However, the static pressure drop increases linearly with a decreasing gas flow rate, while the dynamic pressure drop decreases with an increasing gas flow rate.  
The pressure drop occurs mainly in the cavity zone A and the outlet zone, but it is more remarkable in the cavity zone B than in other zones at a gas flow rate of 200 m\({}^{3}\).h\({}^{-1}\) and rotating speeds over 600 rpm. The results of this study can provide some insights into the dry pressure drop in cross-flow RPB and, thus, they are helpful for the design and scale-up of the device. In the future, a two-phase CFD model could be developed to investigate the wet pressure drop in the cross-flow RPB.  
**Author Contributions:** Conceptualization, C.Z. and W.J.; methodology, C.Z.; software, Z.Y.; validation, C.Z. and Q.Z.; formal analysis, C.Z.; investigation, W.J.; resources, W.J.; writing--original draft preparation, C.Z. and W.J.; writing--review and editing, C.Z. and W.J.; visualization, C.Z.; supervision, Y.L. and G.Q.; funding acquisition, C.Z. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the State Key Laboratory of Chemical Engineering, grant number SKL-ChE-19B02 and Scientific and Technological Innovation Programs of Higher Education Institution in Shanxi, grant number 2020L0284.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.  
**Nomenclature**  
\begin{tabular}{l l} \(C_{1},C_{2},C_{1c},C_{2t}\) & Turbulence model constants for velocity field \\ \(g\) & gravity acceleration (m\(\cdot\)s\({}^{-2}\)) \\ \(k\) & turbulent kinetic energy (m\({}^{2}\cdot\)s\({}^{-2}\)) \\ \(p\) & pressure (Pa) \\ \(t\) & time (s) \\ \(u\) & velocity vector (m\(\cdot\)s\({}^{-1}\)) \\ \(\alpha\) & viscous resistance coefficient (m\({}^{-2}\)) \\ \(\beta\) & inertial resistance coefficient (m\({}^{-1}\)) \\ \(\epsilon\) & dissipation rate of turbulent kinetic energy (m\({}^{2}\cdot\)s\({}^{-3}\)) \\ \(\mu\) & molecular viscosity (kg\(\cdot\)m\({}^{-1}\cdot\)s\({}^{-1}\)) \\ \(\mu_{\rm eff}\) & effective viscosity (kg\(\cdot\)m\({}^{-1}\cdot\)s\({}^{-1}\)) \\ \(\mu_{t}\) & turbulence induced viscosity (kg\(\cdot\)m\({}^{-1}\cdot\)s\({}^{-1}\)) \\ \(\rho\) & density (kg\(\cdot\)m\({}^{-3}\)) \\ \end{tabular}