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

Heiko T. Liebel, Saqib Javed and Gunnar Vistnes

Renewable Energy, 2012, vol. 48, issue C, 263-268

Abstract: 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.

Keywords: Convection; Ground-coupled heat pump; Hard rock; Multi-injection rate thermal response test; Thermal borehole resistance; Thermal conductivity (search for similar items in EconPapers)
Date: 2012
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Citations: View citations in EconPapers (15)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:48:y:2012:i:c:p:263-268

DOI: 10.1016/j.renene.2012.05.005

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