Tore Haug-Warberg

On model portability

With the software of various commercial providers becoming mature, portability of models and associated data comes higher and higher on the agenda. CAPE-Open has accomplished a compromise getting various players on the market to communicate and agree on generating and accepting wrappers for their process models and also thermo data, both key issues in the chemical engineerings software world. Improving a step beyond wrappers requires a more basic approach, which allows taking advantage of the model structure. The design method and the used representation of the Modeller project have already proven a great degree of portability as models can be mapped into all major solver environments including Matlab, gProms, and other DAE solvers. We attempt to line out the motivation, the present and the future of this approach.

Ontology approach to model construction

Abstract We suggest to capture the modelling process including the definition of the topology of the model, the balances, transfer laws, kinetics, the required constitutive equations, and the compilation into a hierarchical set of ontologies that capture all these elements in the form of logical rules, basic equations and other objects. This decomposition of the modelling process, combined with the capturing of the rules, enables a flexible handling of the software construction. Some of the pieces may be integrated, whilst others may be outsourced. The latter is possible because of the clear structure. Outsourcing enables the save handling of proprietary knowledge.

A large-scale energy reporting system for the process industry

Abstract Energy management represents an important issue within the process industry. The lack of a unified, simple and consistent standard for energy loss calculations constitutes an obstacle in further progress towards more energy efficient plants and sites. A unified approach in order to assess energy efficiency and identify losses in plants or at complete sites is needed. This paper describes the results of ongoing work in order to improve energy efficiency within Norsk Hydro. This involves a consistent method for energy loss calculations and a reporting system. An important feature of the method for energy loss calculations is that measurement of recipient streams such as cooling water and effluent gas is not needed. The reporting system is based on Web/Intranet/Java technology and an Oracle database. At present, the energy reporting system is implemented and it is running on some test plants. Work for large-scale implementation including Norsk Hydros 200–300 plants worldwide is currently taking place.

On the principles of thermodynamic modeling

Abstract Applied thermodynamics is to a large extent about heterogeneous phase equilibria, and, quite naturally, much effort has been put into the development of more accurate phase models. On the other hand, surprisingly little work has focused on the consistency of thermodynamic frameworks made from independent model contributions. For this purpose a set of syntactic and semantic modeling rules must be established prior to the computer implementation. These rules should be stated in an application independent manner, i.e. there should be no need for a dedicated (commercial) program interface. One possibility is to define the rules implicitly by virtue of operator overloading, and in this paper it is shown that three algebraic operators (+, * and ^) suffice to describe thermodynamic frameworks of arbitrary complexity. The use of operators, as opposed to a dedicated program interface, has the advantage that complex frameworks can be described on the basis of thermodynamic reasoning, and without the knowlegde of any implementation details. This makes model maintenance, exportation, and documentation easier. Examples based on a Helmholtz energy equation-of-state, and a Gibbs energy model with separate activity coefficient models for each of the binaries, are discussed.