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Heat Transfer Experiment and Analysis to Predict the Efficiency of Heat Exchanger for Deep Geothermal System

심부지열 용 동축 열교환기 성능예측을 위한 열전달 실험 및 해석

  • Jung, Kuk-Jin (School of Mechanical, Automotive and Aeronautical Engineering Korea National University of Transportation) ;
  • Jeong, Yoon-Seong (School of Mechanical, Automotive and Aeronautical Engineering Korea National University of Transportation) ;
  • Park, Jun Su (School of Mechanical, Automotive and Aeronautical Engineering Korea National University of Transportation) ;
  • Lee, Dong Hyun (Korea Institute of Energy Research)
  • 정국진 (한국교통대학교 기계자동차항공공학부) ;
  • 정윤성 (한국교통대학교 기계자동차항공공학부) ;
  • 박준수 (한국교통대학교 기계자동차항공공학부) ;
  • 이동현 (한국에너지기술연구원)
  • Received : 2017.04.10
  • Accepted : 2017.05.15
  • Published : 2017.05.31

Abstract

The Heat exchanger for deep geothermal system is very important to enhance the efficiency of the system. The co-axial heat exchanger is used due to the limitation of digging space. The heat transfer on the external surface of outer pipe should be high to receive a large amount of heat from the ground. However, the inner pipe should be insulated to reduce the heat loss and increase the temperature of discharge water. This study made experiment apparatus to describe the co-axial heat exchanger and measure the heat transfer coefficients on the internal and external surface. And the pin-fin was designed and fixed on the internal surface to increase the efficiency of heat exchanger. Finally, we calculated the temperature of discharge water using the heat transfer circuit of co-axial heat exchanger and heat transfer coefficient which from experimental results. The water temperature was reached the ground temperature at -500 m and following the ground temperature. When the water return to the ground surface, the water temperature was decreased due to heat loss. As the pin-fin case, the heat transfer coefficient on the internal surface was decreased by 30% and it mean that the pin-fin help to insulate the inner pipe. However, the discharge water temperature did not change although pin-fin fixed on the inner pipe.

Keywords

References

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