DAMOU, KOUIDERMEDJIDI, AYMEN IMAD EDDINEHARCHOUCHE, Zine el abidine2025-09-162025-09-162025http://dspace.univ-temouchent.edu.dz/handle/123456789/6857The energy analysis of phase-change power cycles aims to analyze and optimize the heat exchanges and energy transformations associated with the vaporization and condensation of the working fluid, with the objective of improving the overall efficiency and performance of thermodynamic systems such as Rankine cycles. Organic Rankine Cycles (ORC), which are variants of traditional steam Rankine cycles using water, are employed when the heat source available for mechanical power generation is of low or medium temperature. The process was modeled using the DWSIM software and validated through a series of simulations. A sensitivity analysis was then conducted to assess the impact of variations in operating conditions—specifically steam flow rate, inlet temperature, and pressure—on the efficiency of the Rankine reheat cycle. The effect of the working fluid’s phase changes on cycle VI performance was also investigated. For optimization, the Design-Expert software was used, applying a Central Composite Design (CCD) combined with quadratic, linear, and 2FI regression models. Three input parameters were considered: steam mass flow rate, inlet temperature, and pressure. The responses analyzed were the isentropic efficiency and the net power output of the cycle. Consequently, this study adopts an integrated approach combining process simulation using DWSIM and optimization via the Response Surface Methodology (RSM), with the goal of simultaneously improving power output and overall efficiency of the Rankine reheat cycle.frCycle, RSM, Design-Expert, puissance, rendement, optimisation.Rankine cycle, RSM, Design-Expert, power output, efficiency, optimization.Thesis