Ground-source heat pump systems with horizontal spiral ground heat exchangers

Proposes a heat transfer model expected to be used in engineering design of the horizontal spiral ground heat exchangers. The model is based on the one-dimensional unsteady heat transfer in an infinite medium, considering the influence of the tube length per unit area and the different effects of long-term mean load and short-term intermittent load. Discusses the influence of the tube length per unit area and the thermal properties of the soil on the performance of the horizontal spiral ground heat exchangers. With an engineering example, calculates the tube length and the area, and compares them with those of vertical systems.