# Liquid Nanofilms' Condensation Inside a Heat Exchanger by Mixed Convection
## 4 Results and Discussion
### Effect of Nanoparticle Types  
In this work, we studied the impact of the nanoparticle type on the mass and heat transfer during liquid film condensation flowing down on a cooled vertical plate. Figure 7a shows that the gas-liquid interface temperature was less important for the water-aluminium nanofluid compared to the water-copper nanofluid and to the basic fluid. This result can be explained by the lower heat capacity and the higher thermal conductivity of the copper nanoparticles compared to the aluminium nanoparticles and to the basic fluid. Figure 8a,b present the evolution of the sensible and latent heat fluxes for different nanofluids and for pure water. The heat transfer was enhanced with the dispersion of the nanoparticles. The sensible and latent heat fluxes were much better for the water-copper nanofluid, due to the higher thermal conductivity and lower heat capacity of the copper nanoparticles compared to the aluminium nanoparticles and to pure water. Figure 9 presents the condensation rate evolution for various nanoparticle types. The liquid film condensation was higher for the copper-water nanofluid compared to the aluminium-water nanofluid and to the pure water, owing to the fact that the dispersion of the nanoparticles enhanced the latent heat flux (Figure 8a). Figure 10 displays the effect of the ambient humidity on the liquid film condensation. The liquid condensation was important for a higher value of the vapour mass fraction \(c_{0}\). Figure 11 illustrates the influence of the thermal flux cooling \(q_{1}\) on the film condensation. This result demonstrates that a rise in flux cooling \(q_{1}\) improved the film condensation. Figure 12 shows that a rise in the mass flow rate \(m_{0L}\) accelerated the film concentration rate. An increase in the mass flow rate \(m_{0L}\) ameliorated the liquid cooling causing an enhancement in the vapour condensation. Figure 13 shows that a rise in the inlet vapour velocity \(u_{0}\) accelerated the cumulated condensation, due to the fact that an increase in \(u_{0}\) precluded the water vapour from being condensed on the liquid film.  
Figure 7: Effect of nanoparticles type on the temperature (**a**) and the vapor concentration (**b**) at the interface liquid-gas: \(T_{0}\) = 293.15 K, \(T_{0L}\) = 293.15 K, \(T_{w}\) = 293.15 K, \(\Phi_{0}\) = 0.03, \(q_{1}\) = \(-\)1000 W/m\({}^{2}\), \(c_{0}\) = 0.3, \(u_{0}\) = 1 m/s, \(m_{0L}\) = 0.015 kg/m.s, H = 1 m, d = 0.015 m, \(p_{0}\) = 1 atm.  
Figure 8: Effect of nanoparticles type on the latent (**a**) and sensible (**b**) heat fluxes: T\({}_{0}\) = 293.15 K, T\({}_{\rm OL}\) = 293.15 K, T\({}_{\rm w}\) = 293.15 K, \(\Phi_{0}\) = 0.03, q\({}_{1}\) = \(-\)1000 W/m\({}^{2}\), \(c_{0}\) = 0.3, u\({}_{0}\) = 1 m/s, m\({}_{\rm OL}\) = 0.015 kg/m,s, H = 1 m, d = 0.015 m, p\({}_{0}\) = 1 atm.  
Figure 10: Effect of inlet vapor mass fraction on the cumulated condensation rate: T\({}_{0}\) = 293.15 K, T\({}_{0L}\) = 293.15 K, q\({}_{1}\) = \(-\)1000 W/m\({}^{2}\), T\({}_{\rm w}\) = 293.15 K, \(\Phi_{0}\) = 0.03, u\({}_{0}\) = 1 m/s, m\({}_{0L}\) = 0.015 kg/m.s, H = 1 m, d = 0.015 m, p\({}_{0}\) = 1 atm.  
Figure 12: Effect of inlet liquid mass flow on the cumulated condensation rate: T\({}_{0}\) = 293.15 K, T\({}_{0L}\) = 293.15 K, T\({}_{\rm w}\) = 293.15 K, \(\Phi_{0}\) = 0.03, \(c_{0}\) = 0.3, q\({}_{1}\) = \(-\)1000 W/m\({}^{2}\), u\({}_{0}\) = 1 m/s, H = 1 m, d = 0.015 m, p\({}_{0}\) = 1 atm.