Numerical Challenges in Simulation of a Generalized Vapor Compression Refrigeration System

VapCyc is a vapor compression refrigeration simulation tool which features charge management and component inter-changeability. In addition to the four basic cycle components, additional components, such as pipes, bypass valves and various auxiliary heat exchangers can be added to the system at run-time, rather than design time, making the simulation very user-friendly. The simulation is achieved through the solution of the system level conservation laws of mass and energy, which are satisfied through the evaluation of the performance relations of individual component models. This simulation technique presents numerical challenges. This paper presents the system level conservation laws and addresses the numerical challenges of convergence criteria, as well as equation and variable scaling. In addition, a methodology of estimating the solution over a wide range of refrigeration applications and refrigerants, to assist the numeric solver is developed.