Multi-Objective Optimization of Parallel Cross Multi-Effect Desalination Systems with Thermal Vapor Compression

The current work presents a mathematical model to study the performance of a multi-effect desalination system of parallel cross feed arrangement with thermal vapor compression (MED-PCF-TVC). Using energy and mass conservation laws, the system performance is evaluated to determine performance ratio among other operational parameters. Heat transfer analysis is performed to estimate specific heat transfer area. Furthermore, a multi-objective optimization method is used to find the maximum performance ratio (PR) and minimum specific heat transfer area (sA) for MED-PCF-TVC with (N) effects. This study investigates two cases of multi-objective optimization. The first case is performed to find the optimum PR at minimum sA with priority to minimize sA, while the second case considers the optimum PR at minimum sA with priority to maximize PR. Results show that for MED system with “N” number of effects, the optimum PR is obtained when the ejector is located after effect [(N/2) – 1] for the first case. For the second case, the optimum PR is attained when the ejector is located after [(N/2) + 1] effect. In addition, the optimum motive steam pressure where the PR is maximized and sA is minimized is found to be 1500 kPa for each case and each MED system.