On Closure Relations for Dynamic Vapor Compression Cycle Models

Models of closure relations, or the expressions that relate the heat transfer coefficients and frictional pressure losses to other variables of the vapor-compression cycle, can have a significant impact on the performance on the overall cycle behavior. We explore three different approaches that may be used in formulating these closure models, and show that approaches that impose a nonlinear algebraic coupling can impose significant computational challenges. In comparison, models that incorporate lowpass dynamics can effectively decouple this nonlinear behavior,resulting in simulations that are faster and demonstrate more realistic and robust behavior.