TRNSYS g-function generator using a simple boundary condition

• Published in: Energy and buildings 2018-08, Vol.172, p.192-200
• Main Author: Kim, Eui-Jong
• Format: Article
• Language: English
• Subjects: Boundary conditions; Duct storage model; Finite line source model; Function generators; Ground heat exchanger; Heat exchangers; Heat pumps; Heat transfer; Response functions; Thermal response; Thermal response function; TRNSYS
• ISSN: 0378-7788; 1872-6178
• DOI: 10.1016/j.enbuild.2018.05.014

Ground thermal response functions, also well-known as g-functions, have been extensively used for sizing ground heat exchangers and performance analyses of ground coupled heat pump (GCHP) systems. A general approach used to generate g-functions is to define a wall boundary, e.g., uniform temperatures or uniform heat transfer rates. In this work, a TRNSYS g-function generator is proposed that uses the uniform heat transfer rates as a boundary to the finite line source (FLS) model. This boundary can be easily applied to the FLS model and the generating process is computationally rapid. The duct storage (DST) model—TRNSYS type 557—are used to test the proposed FLS-based g-function model. Results showed that the DST model was in good agreement with the proposed models but deviated with respect to the other boundary-based models. However, discussions on which the boundary is realistic are not yet completely concluded with this work since the DST model itself uses several simplifications.