Pile foundations or energy piles serve as ground heat exchangers (GHEs) of ground source heat pump system (GSHP) in some cases. Modeling this kind of GHE is important in the system design. This paper built a new practical numerical model for the energy pile with spiral coils. This model includes a 1-D transient convection-diffusion sub-model for the fluid domain and a 1-D transient diffusion sub-model for the solid domain. The fluid model and the solid model can be solved by a sequential computing algorithm. The two sub-models were compared with analytical models respectively, and filed test data was used to verify the whole model. Results showed that this model is accurate. (C) 2015 Elsevier Ltd. All rights reserved.