• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.385-395
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• 2009

In this study, a series of numerical analysis has been accomplished on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) in a geothermal heat pump system (GHP) considering the circulating fluid, pipe, grout and soil formation. A finite element analysis program, ABAQUS, was employed to evaluate the temperature distribution on the cross section of the U-loop system involving HDPE pipe/grout/formation and to compare sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system. Especially, the latticed pipe is equipped with a thermal insulation zone in order to reduce thermal interference between the inflow pipe and the outflow pipe. Also, a thermal stress analysis was performed with the aid of ABAQUS. 3-D finite volume analysis program, FLUENT, was adapted to analyze a coupled system between fluid circulation in the pipe and heat transfer and simulate an operating process of the closed-loop vertical ground heat exchanger. In this analysis, the effect of the thermal properties of grout, rate of circulation pump, distance between the inflow pipe and the outflow pipe, and the effectiveness of the latticed HDPE pipe system are taken into account.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.583-587
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• 2009

This paper presents a series of numerical simulations on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) equipped in a geothermal heat pump system (GHP). A 3-D finite volume analysis (Fluent) was used to simulate the operating process of the closed-loop vertical ground heat exchanger by considering the effect of the thickness of HDPE pipe and grout thermal properties, distance between the inflow and outflow pipes, and the effectiveness of the latticed HDPE pipe system. It was observed that the thermal interference between the two strands of U-loop is of importance in determining the efficiency of the ground heat exchanger, and thus it is highly recommendable to modify the cross section configuration of the conventional U-loop system by including a thermally insulating latice between the two strands.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1638-1646
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• 2008

This paper presents a series of numerical simulations on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) equipped in a geothermal heat pump system (GHP). A 2-D finite element analysis, ANSYS, was employed to evaluate the temperature distribution on the borehole cross section involving HDPE pipe/grout/soil formation to compare the sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system which is equipped with a thermally insulating latice in order to reduce thermal interference between the inflow and outflow pipes. In addition, a 3-D finite volume analysis (Fluent) was used to simulate the operating process of the closed-loop vertical ground heat exchanger by considering the effect of grout's thermal properties, rate of circulation pump, distance between the inflow and outflow pipes, and the effectiveness of the latticed HDPE pipe system. It was observed that the thermal interference between the two strands of U-loop is of importance in determining the efficiency of the ground heat exchanger, and thus it is highly recommendable to modify the cross section configuration of the conventional U-loop system by including a thermally insulating latice between the two strands.