Dynamic Simulation of Ground Source Heat Pump with a Vertical U-tube Ground Heat Exchanger

수직형 U자 관 지중 열교환기를 갖는 지열원 열펌프의 동적 시뮬레이션

  • Lee, Myung-Taek (Graduate School, Kookmin University) ;
  • Kim, Young-Il (School of Architecture, Seoul National University of Technology) ;
  • Kang, Byung-Ha (School of Mechanical and Automative Engineering, Kookmin University)
  • 이명택 (국민대학교 대학원) ;
  • 김영일 (서울산업대학교 건축학부) ;
  • 강병하 (국민대학교 기계.자동차 공학부)
  • Published : 2007.05.10

Abstract

GHX (Geothermal Heat Exchanger) design which determines the performance and initial cost is the most important factor in ground source heat pump system. Performance of GHX is strongly dependent on the thermal resistance of soil, grout and pipe. In general, GHX design is based on the static simulation program. In this study, dynamic simulation has been peformed to analyze the variation of system performance for various GHX parameters. Line-source theory has been applied to calculate the variation of ground temperature. The averaged weather data measured during a 10-year period $(1991\sim2000)$ in Seoul is used to calculate cooling and heating loads of a building with a floor area of $100m^2$. The simulation results indicate that thermal properties of borehole play significant effect on the overall performance. Change of grout thermal conductivity from 0.4 to $3.0W/(m^{\circ}C)$ increases COP of heating by 9.4% and cooling by 17%. Change of soil thermal conductivity from 1.5 to $4.0W/(m^{\circ}C)$ increases COP of heating by 13.3% and cooling by 4.4%. Change of GHX(length from 100 to 200 m increases COP of heating by 10.6% and cooling by 10.2%. To study long term performance, dynamic simulation has been conducted for a 20-year period and the result showed that soil temperature decreases by $1^{\circ}C$, heating COP decreases by 2.7% and cooling COP decreases by 1.4%.

Keywords

References

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