Identifying optimal thermodynamic paths in work and heat exchange network synthesis

and Heat Exchange Network Synthesis Haoshui Yua, Chao Fub*, Matias Viksea, Chang Hec, Truls Gundersena a Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjoern Hejes v. 1A, NO-7491 Trondheim, Norway b SINTEF Energy Research, Kolbjoern Hejes v. 1A, NO-7491 Trondheim, Norway c School of Chemical Engineering and Technology, Sun Yat-sen University, 519082 Zhuhai, China fuchao83@hotmail.com Abstract: The Process Synthesis problem referred to as Work and Heat Exchange Networks (WHENs) is an extension of the classical HENs problem considering only temperature and heat. In WHENs, additional properties are pressure and work, and strong interactions exist between temperature, pressure, work and heat. The actual sequence of heating, cooling, compression and expansion for pressure changing streams will affect the shape of the Composite and Grand Composite Curves, the Pinch point, and the thermal utility demands. Even stream identities (hot or cold) will sometimes change. The identification of the optimal thermodynamic path from supply to target state for pressure changing streams becomes a primary and fundamental task in WHENs. An MINLP model has been developed based on an extension of the Duran-Grossmann model (that can handle variable temperatures) to also consider changing stream identities. Three reformulations of the extended Duran-Grossmann model have been developed and tested for two examples.