Real-Time Modeling of Liquid Cooling Networks in Vehicle Thermal Management Systems 2008-01-0386

This paper describes a ‘toolbox’ for modeling liquid cooling system networks within vehicle thermal management systems. Components which can be represented include pumps, coolant lines, control valves, heat sources and heat sinks, liquid-to-air and liquid-to-refrigerant heat exchangers, and expansion tanks. Network definition is accomplished through a graphical user interface, allowing system architecture to be easily modified. The elements of the toolbox are physically based, so that the models can be applied before hardware is procured. The component library was coded directly into MATLAB / SIMULINK and is intended for control system development, hardware-in-the-loop (HIL) simulation, and as a system emulator for on-board diagnostics and controls purposes.

For HIL simulation and on-board diagnostics and controls, it is imperative that the model run in real-time. This is especially challenging for thermal-fluid networks because there can be differences of several orders of magnitude between the fastest eigenvalues (usually due to pressure development and flow redistribution within the network) and the slowest eigenvalues (usually due to energy storage in metal components). A novel approach called time scale factoring was used to overcome this obstacle, and it is shown that this technique provides sufficient speed and accuracy for the intended application. This method enables real-time simulation of thermal management systems without requiring explicit knowledge of network topology.

Model integrity has been validated by applying it to several test cases. Model capability is shown through a sample application to a sample cooling system. Because of the generic nature of the elements, the toolbox can be applied to a wide variety of fluid networks in commercial, non-commercial, and military vehicles.