Ground-coupled heat pump (GCHP) systems have been applied to obtain shallow-depth geothermal energy with satisfactory energy efficiency. The GCHP uses sustainable ground temperature to emit heat dur-ing summer and vice versa during winter for cooling and heating buildings. Recently, the geothermal energy pile has been developed as an efficient means of reducing the installation cost. With its incorporation, howev-er, the heat exchange behavior of the energy pile becomes more complex than typical GCHP systems buried in the ground, owing to the incorporation of the pile and grout surrounding the ground heat exchanger (GHE). Moreover, when a coil-type heat exchanger is employed in the energy pile to enhance the heat exchange effi-ciency, current analytical methods, e.g. the line source model and cylindrical source model, may fail to predict realistic heat exchange performance because of the intricate geometry of the spiral coil. Hence, in this paper, a new spiral coil source model and its analytical solution were developed to consider the 3-dimensional shape effects of a spiral coil type GHE and the radial dimension effects using Green’s function. The spiral coil source model prediction results were then compared with other analytical model results to assess the validity of the model. A 2-dimensional axisymmetric finite element model was also developed to simulate the realistic heat exchange behavior of a spiral coil-type GHE, where a general form of a heat diffusion equation applica-ble to the energy pile was considered. The numerical model was applied in the ABAQUS program to simulate thermal response tests conducted in a model chamber, and its validity was investigated through comparison of the predictions with test measurements.
코일형 지중열교환기의 정확한 설계 개발을 위하여 코일형 지중열교환기의 열전달 메커니즘 특성을 연구하였다. 이를 위해 코일형 지중열교환기의 3차원 코일 열원 형상과 유한한 코일 열원 효과를 고려한 3차원 해석모델 spiral coil source model을 제안하였고 Green’s function을 이용하여 해석해를 개발하였다. 개발된 해석모델 spiral coil source model은 기존 해석모델들과의 비교, 분석, 검증을 하였고 이를 통해 코일열원이 촘촘하게 되면 cylindrical source model과 같은 특성을 보이며 코일열원이 느슨하게 되면 ring-coil source model과 유사한 특성을 보이며 코일열원이 일직선이 되면(코일반경이 0일 때(r0=0)) finite line source model과 동일한 형태를 얻을 수 있다. ABAQUS를 이용하여 기존 해석모델과의 비교 결과를 바탕으로 3차원 코일 열원을 축대칭의 ring-coil 열원으로 가정하여 열전달 수치해석을 수행하였다. 개발된 열전달 수치해석모델을 통해 에너지파일과 수직 밀폐형 열교환기개발된 해석모델과 수치해석모델은 본 연구실에서 기수행된 열응답시험 측정 결과와 비교를 통해 검토하였고 해석모델의 해석해 매개변수 연구를 통해 해석모델의 특성 파악 및 spiral coil source model을 통한 지반 내 열전달 특성을 살펴보았다.
