Papers by Johan Windahl:

Title: Optimization-friendly thermodynamic properties of water and steam
Authors: Marcus Åberg, Johan Windahl, Håkan Runvik and Fredrik Magnusson
Abstract:This paper describes the development of an optimization-friendly thermodynamic property model of water and steam that covers liquid, vapor, 2-phase as well as the super-critical region. All equations are at least twice continuously differentiable with respect to all model variables and can be used in dynamic optimization problems solved by efficient derivative-based algorithms. The accuracy has been verified against the industry standard IAPWS 97 and performance and robustness has been tested by solving a trajectory optimization problem where the start-up time of a gas power plant has been minimized while satisfying constraints on temperature gradients, pressure and flows. Simulations of various plant models have also been performed to verify and benchmark the implementation. The results show that the new media can be used in both solving dynamic optimization and simulation problems yielding reliable results. The new media has been integrated into Modelon’s Thermal Power library 1.13.
Links: Full paper