Multi-Objective Optimal Design of an Organic Rankine Cycle Plate Heat Exchanger with Phase Change

In this study, a multi-objective optimization method founded on genetic algorithms is implemented to obtain optimized geometrical parameters for the plate heat exchanger configuration which causes pressure drop minimization and overall heat transfer coefficient maximization. This heat exchanger is basically designed as an evaporator of Organic Rankine Cycles by considering R123 as the working fluid. It is supposed that water vapor with entrance temperature of is deployed as hot fluid. A multi-objective optimization method founded on genetic algorithms is implemented to optimize geometrical parameters for the heat exchanger configuration which leads to pressure drop minimization and overall heat transfer coefficient maximization. Two objective functions are conflicting with each other that both single and two-phase flow scenarios are also addressed. In the present optimization method, a Pareto solution is used which permits the derivation of a mathematical relation between the two objective functions simultaneously and yields the optimal geometrical parameters for heat exchangers subjected to constraints associated with the Pareto optimal set. A detailed sensitivity analysis has been conducted for each geometrical parameter and the effects of each parameter on key design characteristics have been evaluated. Both objective functions of the overall heat transfer coefficient and the total drop are reduced, by increasing the ports’ diameter and, due to increasing the thickness of each plate inside the plate heat exchanger, the two-sheet spacing will naturally reduce.