A modified three-dimensional numerical model for predicting the short-time-step performance of borehole ground heat exchangers

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

19 Scopus Citations
View graph of relations


  • C. K. Lee


Original languageEnglish
Pages (from-to)618-627
Journal / PublicationRenewable Energy
Publication statusPublished - 1 Mar 2016


A modified three-dimensional numerical model for the borehole ground heat exchangers was proposed which took into account the effect of grout thermal capacitance and fluid circulation period inside the U-tube in a short-time-step analysis. The present model was validated by experimental data from others. It was found that the fluid temperature along the U-tube changed abruptly at the interface between the entering and the existing fluid inside the borehole. Before the entering fluid travelled to the bottom of the U-tube, the borehole was only partly-loaded. The difference in the simulated fluid leaving temperatures between the long- and short-time-step approaches could be up to 3 °C when a periodic intermittent load, common during the low-load season, was applied. This implied that a short-time-step model should be used in a long-term dynamic system simulation.

Research Area(s)

  • Borehole, Ground heat exchanger, Ground-source heat pump, Short-time-step, U-tube