# Study of the Impact of PV-Thermal and Nanofluids on the Desalination Process by Flashing
## 1 Introduction  
Water scarcity is a complex and difficult problem. Desalination uses a large amount of energy, and it is difficult to advocate for a technology that increases fossil fuel-based energy consumption. Remote coastal areas in the Middle East, Africa, and the Mediterranean and Caribbean islands are suffering from acute shortages of drinking water [1; 2; 3]. It is anticipated that by 2025, more than about 60% of the world's population will suffer from serious drinking water shortages [4]. Conventional desalination techniques, such as multi-stage flash (MSF) desalination, vapor compression (VC), reverse osmosis (RO), membrane distillation (MD), and electrodialysis (ED), require significant thermal energy to function. As more places face water scarcity, desalination is considered as a possible answer. However, energy and financial requirements limit how widely that process can be used. We believe that solar energy is the logical response to these limitations and can power thermal and electrical desalination systems. Studies [5; 6] have shown that solar desalination can be achieved, in particular, in areas where solar intensity is high and there is a lack of fresh drinking water. Therefore, this research was undertaken to study the impact of solar energy and nanofluids on the desalination process. [PERSON] et al. [7] presented a general model to simulate the multiple stage flash distillation (MSF) process. The model was implemented within the Camel-ProTM Process Simulator. Severalvalidation tests were conducted to confirm that the model is an efficient tool for MSF plant design and prediction of the most important variables in the MSF process. Lumped parameter dynamic models were developed in [PERSON]'s Ph.D. thesis [8] or using the MSF once through (MSF-OT) and the MSF brine circulation (MSF-BC) processes. The models were coded using the gPROMS modeling program. The model predictions for both MSF-OT and MSF-BC in steady state and dynamic conditions showed good agreement with data from existing MSF plants with an error less than 1.5%. The methodology proposed in [9] provides a set of modular simulations of components that allow the creation of complex models used to optimize the full water desalination supply chain. The optimization scheme included mathematical programming (MP) models that were solved by an external MP solver for Saudi Arabia, which is considered the worldwide leader in desalinated water capacity. [PERSON] [10] reported on a steady-state mathematical model of the multi-effect thermal vapor compression (ME-TVC) desalination system. The ME-TVC desalination system in this paper was developed using the Engineering Equations Solver (EES) to evaluate the model system performance. The model validity was examined against three commercial ME-TVC units and the end results were good. In addition, a MATLAB algorithm solution was developed and used to solve model equations, where a different number of effects were tested to maximize the gain ratio of the process. A computational field model for the flashing process in the evaporation zone inside a flashing chamber with nanofluid-based solar collectors was developed by the author of [11] using two-phase volume of fluid (VOF) formulation. The model was then applied to investigate the effects of variations in the inlet brine flow rate and inlet brine temperature for both finite and infinite flashing process classifications. The predictions were analyzed to estimate MSF design factors, such as the non-equilibrium temperature difference and flashing efficiency. An integrated system using a flashing desalination technique coupled with a nanofluid-based solar collector as a heat source was presented in [12] to study both the effect of different operating modes and that of the variation of functioning parameters and weather conditions on freshwater production using nanofluids. The flashing unit was produced using a similar construction design technique of a commercial multi-stage flashing (MSF) plant.