Control Volume Interfaces: A Unique Tool for a Generalized Fluid Network Modeler

Over the past 15 years, the industry standard tool for thermal analysis, SINDA, has been expanded to include advanced thermodynamic and hydrodynamic solutions (“FLUINT”). With the recent culmination of the unique modeling tools, SINDA/ FLUINT has arguably become the most complete general-purpose thermohydraulic network analyzer that is available. Traditional network elements for fluid circuit analyzers include control volumes and flow passages. During the development of modeling tools capable of handling phasic nonequilibrium within SINDA/ FLUINT, several new network elements were created as by-products. This paper describes one of them: control volume interfaces or “ifaces” for short. Ifaces are used to describe how one control volume abuts another. While originally developed to model liquid-vapor interfaces within two-phase control volumes, they can also be used to describe pistons, spring bellows, liquid slugs, and curved interfaces such as those between bubbles and liquid as well as those within capillary structures (e.g., sintered wicks). More importantly, they can be used as an imaginary film to subdivide quasi-stagnant control volumes, extending the reach of a 1D network into certain 2D and 3D problems. Despite their abstract nature, ifaces have been well received by analysts for a variety of modeling tasks.