Bond-Graph Based Simulation of Thermodynamic Models

Abstract

Conventional bond graphs are incompetent to handle thermodynamic systems with flowing fluid and phase change, such as heat engines and refrigeration cycles. Sophisticated bond-graph software for purposes of simulation is widely available for the systems addressable by conventional bond graphs, but heretofore there was no bond-graph software that could simulate the thermodynamic systems of concern. The author has previously published descriptions of a compatible extension to conventional bond graphs, which accommodates these systems through the use of what are known as convection bonds. Simulation of these models required ad hoc writing of the differential equations, however, a difficult task. The present brief announces the availability of software, based on a combination of convection and conventional bond graphs, which considerably expedites the simulation of thermodynamic and hybrid systems. The software is written in MATLAB ® and is freely downloadable from the internet. It allows modeling and simulation to be carried out with a minimum knowledge of thermodynamics. Data characterizing the thermodynamic properties of 35 different pure substances and wet air are accessed as needed.