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하천-충적대수층계의 강변여과수를 열원으로 이용하는 지하수 열펌프 시스템의 계절별 입구온도와 효율성 평가
한찬(Chan Hahn),전재수(Jae-soo jeon),윤운상(Yoon-Sang Yoon),한혁상(Hyok-Sang Han),한정상(Jeong-Sang Hahn) 한국지열·수열에너지학회 2007 한국지열에너지학회논문집 Vol.3 No.2
Unconsolidated and permeable alluvial deposit composed of sand and gravel is distributed along the fluvial plain at the Iryong study area. Previous studies on the area show that a single alluvial well can produce at least 1,650m3d-1 of bank infilterated shallow groundwater(BIGW) from the deposit. This study is aimed to evaluate and simulate the influence that seasonal variation of water levels and temperatures of the liver have an effect on those of BIGW under the pumping condition and also to compare seasonal variation of COPs when indirectly pumped BIGW or directly pumped surface water are used for a water to water heat pump system as an heat source and sink using 3 D flow and heat transport model of Feflow. The result shows that the magnitude influenced to water level of BIGW by fluctuation of river water level in summer and winter is about 48% and 75% of Nakdong river water level separately. Seasonal change of river water temperature is about 23.7 ℃, on other hand that of BIGW is only 3.8℃. The seasonal temperatures of BIGW are ranged from minimum 14.5℃ in cold winter(january) and maximum 18.3℃ in hot summer(July). It stands for that BIGW is a good source of heat energy for heating and cooling system owing to maintaining quite similar temperature(16℃) of background shallow groundwater. Average COPh in winter time and COPc in surnmer time of BIGW and surface water are estimated about 3.95, 3.5, and about 6.16 and 4.81 respectively. It clearly indicates that coefficient of performance of heat pump system using BIGW are higher than 12.9% in winter time and 28.1% in summer time in comparision with those of surface water.
지하수류가 밀폐형 천공 지중열교환기 성능에 미치는 영향(1)
한정상,한찬,윤운상,김영식,Hahn, Jeong Sang,Hahn, Chan,Yoon, Yun Sang,Kiem, Young Seek 한국지하수토양환경학회 2016 지하수토양환경 Vol.21 No.3
To analyze the influence of various groundwater flow rates (specific discharge) on BHE system with balanced and unbalanced energy loads under assuming same initial temperature (15℃) of ground and groundwater, numerical modeling using FEFLOW was used for this study. When groundwater flow is increased from 1 × 10<sup>−7</sup> to 4 × 10<sup>−7</sup>m/s under balanced energy load, the performance of BHE system is improved about 26.7% in summer and 22.7% at winter time in a single BHE case as well as about 12.0~18.6% in summer and 7.6~8.7% in winter time depending on the number of boreholes in the grid, their array type, and bore hole separation in multiple BHE system case. In other words, the performance of BHE system is improved due to lower avT in summer and higher avT in winter time when groundwater flow becomes larger. On the contrary it is decreased owing to higher avT in summer and lower avT in winter time when the numbers of BHEs in an array are increased, Geothermal plume created at down-gradient area by groundwater flow is relatively small in balanced load condition while quite large in unbalanced load condition. Groundwater flow enhances in general the thermal efficiency by transferring heat away from the BHEs. Therefore it is highly required to obtain and to use adequate informations on hydrogeologic characterristics (K, S, hydraulic gradient, seasonal variation of groundwater temperature and water level) along with integrating groundwater flow and also hydrogeothermal properties (thermal conductivity, seasonal variation of ground temperatures etc.) of the relevant area for achieving the optimal design of BHE system.