Multi-injection rate thermal response test with forced convection in a groundwater-filled borehole in hard rock

Research output: Contribution to journalArticle


Convection is shown in earlier studies to improve the thermal contact between heat exchanger and borehole wall in water-filled boreholes. This study investigates the effect of convection on the required borehole length for a ground-coupled heat pump installation. Artificial convection was induced by an ordinary groundwater pump during a multi-injection rate thermal response test (MIR-TRT). For comparison, a second MIR-TRT was performed without pumping of groundwater. The required borehole length was estimated for a ground-coupled heat pump installation supplying a Swedish single-family house. The estimates are based on the results from the MIR-TRTs for thermal conductivity and borehole resistance. The results show linear decrease in required borehole length with increasing heat input rate during the MIR-TRT without pumping of groundwater due to buoyancy-driven convection. An artificial convection stronger than buoyancy-driven convection during the MIR-TRT with pumping of groundwater reduced the required borehole length by 9 %–25 % depending on the heat input rate.


External organisations
  • Norwegian University of Science and Technology
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Energy Systems
  • Building Technologies


  • Convection, Ground-coupled heat pump, Multi-injection rate thermal response test
Original languageEnglish
Pages (from-to)263-268
Number of pages6
JournalRenewable Energy
Issue numberDecember 2012
Publication statusPublished - 2012
Publication categoryResearch