Development of a novel spiral coil ground heat exchanger model considering axial effects

This paper presents the development of a novel spiral heat source model based on the Green's function method that takes into account axial effects. This new model is based on the principle of spatial superposition of heat sources to model the varying thermal response in spiral coil heat exchangers (SCHE) as a function of depth. It also proposes new input parameters, inlet fluid temperature and mass flow rate instead of heat transfer rate, which is now obtained by performing an iterative process. To perform simulations of time-varying thermal loads, a temporal superposition along with an aggregation algorithm is developed. The new model is compared to other models for both constant and variable loads to evaluate the importance of taking into account axial effects and the variation of the thermal response with depth in SCHEs.