수치해석을 통한 수직 밀폐형 지중열교환기 단면의 열전달 효율 분석

Abstract

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) in a geothermal heat pump system (GHP). A 2-D finite element analysis adopting ANSYS was employed to evaluate the temperature distribution over the cross section of the U-loop system involving HDPE pipe/grout/soil to compare the sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system, which is equipped with a thermally insulating lattice in order to reduce thermal interference from the inlet pipe to outlet pipe. In addition, a 3-D finite volume analysis (FLUENT) was used in simulating the operation of the closed-loop vertical ground heat exchanger with the consideration of the effect of grout’s thermal properties, the rate of circulation pump, the distance between the inlet and outlet 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. Therefore, it is highly recommended to modify the configuration of the conventional U-loop system by equipping the thermal insulating lattice between the two pipe strands.