• An Influence of Groundwater Flow on Performance of Closed Borehole Heat Exchangers (Part-2)
  • Hahn, Jeongsang;Kiem, Youngseek;Lee, Juhyun;Lee, Byoungho;Hahn, Chan;
  • Hans Engineering Co., Ltd.;Hans Engineering Co., Ltd.;Hans Engineering Co., Ltd.;Korea Groundwater and Geothermal Energy Association;Geogreen 21;
  • 지하수류가 밀폐형 천공 지중 열교환기 성능에 미치는 영향(2)
  • 한정상;김영식;이주현;이병호;한찬;
  • (주)한서엔지니어링;(주)한서엔지니어링;(주)한서엔지니어링;한국지하수지열협회;(주) 지오그린21;
Abstract
An increase of groundwater flux in BHE system creates that ground temperature (locT) becomes lower in summer and higher in winter time. In other words, it improves significantly the performance of BHE system. The size of thermal plume made up by advection driven-flow under the balanced energy load is relatively small in contrast to the unbalanced energy load where groundwater flow causes considerable change in the size of thermal plume as well ground temperature. The ground temperatures of the up gradient and down gradient BHEs under conduction only heat transport are same due to no groundwater flow. But a significant difference of the ground temperature is observed between the down gradient and up gradient BHE as a result of groundwater flow-driven thermal interference took placed in BHE field. As many BHEs are designed under the obscure assumption of negligible groundwater flow, failure to account for advection can cause inefficiencies in system design and operation. Therefore including groundwater flow in the design procedure is considered to be essential for thermal and economic sustain ability of the BHE system.

Keywords: BHE (borehole heat exchanger);avT (average loop temperature);locT (local ground temperature);Unbalanced energy load;Balanced energy load;

References
  • 1. Casasso, A. and Sethi. R., 2014, Efficiency of closed loop geothermal heat pumps, A sensitivity analysis. Renewable Energy 62, 737-746
  •  
  • 2. Chiasson, A.d., Rees, S.J., and Spitter, J.D., 2000, Preliminary assessment of the effects of groundwater flow on closed loop ground-source heat pump system. ASHRAE Transections 106(1), 380-393.
  •  
  • 3. Dehkordi, S.E. and Schincariol, R.A., 2014, Effect of thermalhydrogeological and borehole heat exchanger properties on performance and impact of vertical closed loop geothermal heat pump systems, Hydro. J., 22(1), 189-203.
  •  
  • 4. Dehkordi, S.E., Schincariol, R.A., and Oloffson, B., 2015, Impact of groundwater flow and energy load on multiple borehole heat exchangers, Groundwater, 53(4), 558-571.
  •  
  • 5. Diersch, H.J.G., Bauer, D., Heaidmann, W., Ruhakk, W., and Schatzl, P., 2010, Finite element formulation for borehole heat exchangers in modeling geothermal heating systems by FEFLOW. FEFLOW white papers, Vol.V, DHI-WASY GmbH, Berlin, Germany.
  •  
  • 6. Diersch, H.J.G., Bauer, D., Heaidmann, W., Ruhakk, W., and Schatzl, P., 2011a, Finite element modeling of borehole heat exchangers systems: Part 1, Fundmentals, Comput. Geosci., 37(8), 1122-1135.
  •  
  • 7. Diersch, H.J.G., Bauer, D., Heaidmann, W., Ruhakk, W., and Schatzl, P., 2011b, Finite element modeling of borehole heat exchangers systems: Part 2, Numerical simulation, Comput. Geosci., 37(8), 1136-1147.
  •  
  • 8. Eskilson, P. and Claesson, J., 1988, Simulation model for thermally interacting heat extraction boreholes, Numerical Heat Transfer, 13(2), 149-165.
  •  
  • 9. Ferguson Grant, 2015, Screening for heat transport by groundwater in closed geothermal systems, Groundwater, 53(3), 503-506.
  •  
  • 10. Fujii, H., Itori, R., Fujii, J., and Uchida, Y., 2005, Optimizing the design of large scale ground-coupled heat pump systems using groundwater and heat trasport modeling. Geothermics, 34(3), 347-364.
  •  
  • 11. Gehlin, S., 2002, Thermal response test method development and evaluation, Doctoral thesis, Lulea University of technology, Lulea, Sweden.
  •  
  • 12. Hahn, J.S., Han, H.S., and Hahn, C., 2010, Geothermal energy : Low enthalphy geothermal heating and cooling system and geothermal power plant, Hanlimwon Publishing Co., Ltd, Seoul, Korea, (14), 10-18.
  •  
  • 13. Hahn, J.S., and Hahn, C., 2015, Groundwater management and it's application, Naeha Publishing Co., Ltd, Seoul, Korea, 422-423.
  •  
  • 14. Hahn. J.S., Hahn, C., Yoon, Y.S., and Kiem, Y.S., 2016, An influence of groundwater flow on performance of closed borehole heat exchangers(Part-1), J. Soil Groundw. Environ., 21(3), 64-81.
  •  
  • 15. He, M., 2012, Numerical modeling of geothermal borehole exchangers systems. PhD thesis, Institute of Energy and Sustainable Development, De Monfort University, Leicaster, UK.
  •  
  • 16. Kavanaugh, S.P. and Rafferty, K., 1997, Gound Source-Heat Pumps: Design of geothermal systems for commercial institutional buildings, ASHRAE, 49-50.
  •  
  • 17. Vienken, T., Schelenz, S., Rink, K., and Dietrich, P., 2015, Sustainable intensive thermal use of the shallow subsurface-a critical view on the Status Qud, Groundwater, 53(3), 356-361.
  •  
  • 18. Wang, H.B., Xie, Y.J., and Qi, C., 2013, Thermal performance of borehole heat exchangers in different aquifers: A case study from Shouguang. IJLCT, 7(4), 253-259.
  •  

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