Parameter Estimation and the Use of Catalog Data with TRNSYS

Abstract

Due to assumptions, idealizations, and detailed specifications often required by existing TRNSYS components, difficulties are encountered in modeling the performance of cataloged components within TRNSYS transient thermal system simulations. A cataloged component is defined as a component whose performance is described by a manufacturer's catalog data. This performance data may be in either tabular or graphical form.

To avoid these difficulties, a method has been developed for modeling cataloged components within TRNSYS. This method defines characteristic performance parameters through the manipulation of the basic equations governing the behavior of the component. These characteristic parameters are often combinations of terms, such as geometric specifications, fin efficiencies, or other quantities that require detailed knowledge of the construction of the component. Such detailed information is generally not found in manufacturers' catalogs. Other terms from the basic equations, such as fluid transport properties, are retained to provide a robust model. This method has been successfully used to predict the performance of sensible heat exchangers, chilled water cooling coils, and direct expansion cooling coils.

Originally developed with the Engineering Equation Solver (EES) software package, the parameter estimation routine has been programmed to operate in the TRNSYS environment. Using a TRNSED interface, an Input Data File, a standard TRNSYS Type, and an optimization subroutine from a library of numerical routines, the best-fit values of the characteristic parameters are determined. These values can then be used in a TRNSYS simulation that utilizes that particular cataloged component.