TRNSYS g-function generator using a simple boundary condition

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.