Pseudo Bond Graphs for Thermal Energy Transport

Bond graphs have been shown to be useful in the modeling of a wide variety of physical dynamic systems, but open systems in which energy is transported across boundaries with mass flow have never been modeled as elegantly as fixed mass systems and their analogs. In this paper a bond graph, building block approach is outlined which allows most of the conceptual and practical advantages of normal bond graph techniques to be retained for systems in which thermal energy transported by a flowing fluid is important. Practical applications include the dynamic modeling of heating and cooling systems involving air and water. The method allows the imposition of a constant causal scheme independent upon the direction of fluid flow. The result is a pseudo bond graph since the use of temperature and heat flow as effort and flow means that the product of effort and flow is not power as in normal bond graphs.