A comprehensive study of Fin-Assisted horizontal ground heat exchanger for enhancing the heat transfer performance

Abstract

A horizontal ground heat exchanger installation is less expensive than a vertical ground heat exchanger, but more land is required. The system’s required pipe length and land area can be decreased by improving the system. On the other side, adding fins is one strategy to increase heat transfer. In this paper, cylindrical fins are explored in horizontal ground heat exchangers for the first time to improve heat transfer and, the overall efficiency of the ground-source heat pump. These fins were examined by varying parameters such as length, diameter, position, and material. The heat transfer rate changes with and without fins were also investigated as soil properties changed. The heat transfer simulations in cooling mode for a 1D-3D model using COMSOL Multiphysics revealed that changing the fin diameter directly affects the outlet temperature and, the non-isothermal pipe flow (niofl) is used for the pipe. There is minimaldifference between improving and increasing the heat transfer rate when the fin length is increased to more than 1 m. Moreover, the distance between the ground heat exchanger and the fin is critical; if it exceeds 5 cm, it loses some effectiveness, although it is still useful for soil recovery. In general, the fin increases the soil contact area, and a fin of length one meter can increase heat transfer per unit of pipe length up to 20.7 %. Comparing horizontal and vertical ground heat exchangers in finned and non-finned modes revealed that both modes increase performance with the fin. Still, the horizontal pipe increases performance by about 3 % more than the vertical spiral with the same number of fins.