Finite difference model of a spiral ground heat exchanger for ground-source heat pumps

Closed loop ground-source heat pumps use electrical energy to drive a refrigeration cycle which extracts heat from the ground during the heating season and rejects heat from the conditioned space during the cooling season. On a seasonal basis, residential ground-source heat pump (GSHP) systems provide three to four times the energy, in the form of heat, to the space as it requires to drive the compressor and fans. This can represent a significant energy reduction over conventional space heating systems.; A horizontal heat exchanger design called the spiral, or slinky, heat exchanger developed at Oklahoma State University optimizes the soil contact area with respect to the trench length.; A finite difference program was developed to model a slinky ground heat exchanger for a residential ground-source heat pump system. Slinky ground heat exchangers are constructed from overlapping spirals of pipe layed flat in the bottom of a trench. To simplify the model, the heat exchanger was simulated as an equivalent length of equally spaced straight pipes.