STUDY ON THE SIMPLIFIED MODEL OF VERTICAL DOUBLE U-PIPE GROUND HEAT EXCHANGER.

A simplified semi-analytical model of vertical double U-pipe ground heat exchanger was established. The validity of the established model is examined by contrasting the figured outcomes with experiment data, emulation results of 3-D numerical model and calculation results of infinite line-source model for different inlet boundary conditions and configurations. After one hour, the semi-analytical model's relative error is less than 0.32% under the boundary condition of given inlet fluid temperature. Under the boundary condition of given total heat input rate, the semi-analytical model's relative error after ten hours is less than 0.11%, while the infinite line-source model's relative error is less than 0.60%. The semi-analytical model is in good agreement with experiment and numerical model, and has higher calculation accuracy than infinite line-source model. [ABSTRACT FROM AUTHOR]