# Study of the Impact of PV-Thermal and Nanofluids on the Desalination Process by Flashing
## 5 Discussion and Analysis
Examining the results presented in Figures 3 and 4 suggests that the higher the nanofluid concentration as a heat transfer fluid, the lower the salt % in the flashed flow leaving the set of the flashing chambers compared to water as the base heat transfer fluid used in the brine preheater. On the other hand, it can also be seen from the figures that the higher the solar radiation, the lower the salt % in the flashed flow. This can be attributed to the fact that higher solar radiation results in higher temperature of the heat transfer fluid and consequently, the brine flow in the preheater entering the flashing chambers. In addition, it was found that the higher the heat transfer fluid temperatures, the higher the brine flow temperatures and the higher the amount of the distilled water evaporated or flashed. It can also be noticed from the results that the salt % in brine was increased progressively in the flashing chambers until reaching its maximum value at the final chamber. Figure 4: Salt % in flashed at 1200 w/m\({}^{2}\). Figure 3: Salt % in flashed flow at 500 w/m\({}^{2}\). Figure 5: Salt % in brine at 500 w/m\({}^{2}\). Figure 6: Salt % in brine at 1200 w/m\({}^{2}\). Figure 8: Flashed flow at 1200 w/m\({}^{2}\). Figure 7: Flashed flow at 500 w/m\({}^{2}\). Figures 7 and 8 display the changes in the flashed flow in each flashing chamber, at different solar radiations, where it can be seen that the flashed flow was reduced progressively and reached its lowest value at the last flashing chamber. The amount of the produced distillate decreased along the  
Figure 10: Availability at 1200 w/m\({}^{2}\). Figure 9: Irreversibility at 1200 w/m\({}^{2}\). different stages and consequently, the flash temperature and pressure profiles decreased; this is due to the increase of the heat of vaporization at lower saturation temperatures and therefore, a lower amount of vapor was extracted from brine. In fact, the data in these figures show that the higher the solar radiation, the higher the temperature; this caused the distillation rate to rise, since a larger amount of vapor can be extracted from saltwater. The results also show that the higher the solar radiation, the higher the flashed flow per chamber. In addition, these results also demonstrated that the higher the nanofluid Ai\({}_{2}\)O\({}_{3}\) concentration, the higher the flashed flow produced during the flashing process compared to water as base heat transfer fluid. In thermodynamics, changes in the state or process of a system cannot be restored to its initial state by changes in the properties of the system without expenditure of energy [21]. An irreversible process increases the entropy of the system in question. The second law of thermodynamics can be used to determine the irreversibility of a process as per Equation (16). In the thermodynamic process, the energy is lost to the surroundings in the form of irreversible energy. However, the remaining amount of energy is defined as the available energy in the process [21]. This thermodynamic principal was applied in the current study of the flashing chamber process, as expressed in Equations (15) and (16) to assess the lost and available energy in the process under question. In particular, Figures 9 and 10 were constructed to demonstrate the variation of irreversibility and the availability at a solar radiation of 1200 w/m\({}^{2}\) during the flashing process at each stage. The results displayed in these figures clearly show that the irreversibility was reduced by using nanofluid Ai\({}_{2}\)O\({}_{3}\) at a higher concentration compared to water as base heat transfer fluid. Furthermore, the higher the concentration of Ai\({}_{2}\)O\({}_{3}\), the higher the availability observed at the last flashing chamber. However, the availability was progressively reduced toward the last flashing chamber.