Numerical simulation and experimental verification of horizontal ground heat exchangers

The horizontal ground heat exchangers (GHEs) provide a favorable alternative for ground-coupled heat pumps in countryside houses because of the relatively lower installation cost compared to vertical GHEs. Currently, the widely used horizontal GHE (HGHE) configurations are the straight pipe heat exchanger and slinky-coil heat exchanger. A novel pipe configuration of vertical spiral coils is proposed in this study. An experimental setup for the three horizontal GHEs has been established and their thermal performances have been investigated experimentally. The 3-D numerical models are developed to simulate the heat transfer process of the three types of configurations. Comparisons between the experimental and predicted data show a good agreement during the test period. Both the measured and the predicted results exhibit that the vertical spiral HGHE has the highest heat transfer rate compared to the other two HGHEs. This may be caused jointly by the largest heat transfer area with the surrounding soil and the less thermal influences by the ambient air temperature variations.