Design of a Thermo-hydraulic Model Library in Modelica

A new language called Modelica for hierarchical physical systems modeling is developed in an international effort. The main objectives are to make it easy to exchange models and model libraries between tools and to use object-oriented constructs to facilitate the reuse of modeling knowledge. To promote the idea of a unified modeling language for continuous and hybrid systems, public domain model libraries for basic models are developed in various application domains. This paper deals with the design of a base library for thermo-hydraulic applications. Requirements for the library are derived from representative simulation examples and special care is taken to cover the basic physical phenomena broadly. Accurate and fast calculations for thermodynamic properties of fluids constitute a very important and intricate part of thermo-hydraulic calculations, therefore they are given much attention. The state equations for the transport of mass, momentum and energy are formulated in a very general way in order to allow application oriented simplifications in derived classes. Constitutive equation submodels (e. g., for heat transfer coefficients) complete the set of basic building blocks. Modelicas unique language features1 of class parameters and multiple inheritance are extensively used in order to structure the library for intuitive use by model-users and maximum code reuse by model-developers. The library is under development now.