Solid cylindrical heat source model for pile ground heat exchangers with spiral coils

A pile ground heat exchanger with spiral coils is devised to overcome the shortcomings in configuration of existing pile ground heat exchangers.A solid cylindrical heat source model is proposed for the pile ground heat exchanger based on analysis of two classical models for vertical borehole ground heat exchangers,and two analytical expressions of model solution are acquired by the Green function method.The calculation and analysis illustrate that the proposed new solid cylindrical heat source model is applicable to the pile ground heat exchanger with spiral coils,and the new model is superior to the traditional line source model and the hollow cylindrical source model when used for short-term thermal analysis of borehole ground heat exchangers.