Comparative Performance Analysis of Multi-Stage Flash (MSF) and Multi-Effect Desalination (MED) Seawater Desalination Systems Using Exergy Analysis and Economic Evaluation

Abstract

Freshwater scarcity is one of the most pressing and increasingly critical global challenges driven by population growth, industrial expansion, and climate change This has made seawater desalination a strategic solution for providing sustainable water resources, particularly in arid and semi-arid regions This study aims to conduct a comprehensive comparison between Multi-Stage Flash (MSF) and Multi Effect Desalination (MED) systems through thermal, energy, exergy, and economic analyses, using simulation models developed in Aspen Plus for a nominal production capacity of (1,000 m³/h) Identical operating conditions were applied to ensure a consistent and fair comparison The simulation results showed that the (MED) system provides superior thermal performance and more efficient utilization of thermal energy as a result of the reuse of latent heat between successive effects, leading to reduced steam consumption and improved utilization of thermal energy On the other hand, the exergy analysis indicated that the (MSF) system achieved higher exergy efficiency and a lower exergy destruction rate than the (MED) system within the investigated feed water temperature range, with the performance of both systems improving as the feed water temperature increased The results also showed that the water recovery ratio of the (MSF) system remained higher than that of the (MED) system over the investigated salinity range, while increasing the feed water temperature improved the recovery ratio of the (MED) system and resulted in converging performance between the two systems at higher temperatures From an economic perspective, the (MSF) system clearly outperformed the (MED) system under the economic scenario considered, achieving higher Net Present Value (NPV), Annual Rate of Return (ARR), and Profitability Index (PI), in addition to a shorter capital payback period Accordingly, the findings indicate that the selection of desalination technology depends on the evaluation criterion and operating conditions            (MED) represents a suitable option when priority is given to thermal efficiency and reducing thermal energy consumption, whereas (MSF) provides better exergy and economic performance according to the present results, together with high operational stability These findings provide a basis for multi-criteria decision-making in the design and selection of large-scale thermal desalination systems.