• 제목/요약/키워드: 이산화탄소의 열전달

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수평관내 $CO_2$의 초임계 영역내 열전달에 관한 연구 (The heat transfer characteristics of supercritical $CO_2$ in a horizontal tube)

  • 오후규;이동건;손창효
    • Journal of Advanced Marine Engineering and Technology
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    • 제29권5호
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    • pp.526-532
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    • 2005

  • The cooling heat transfer coefficient of $CO_2$(R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump. a mass flow meter. a pre-heater and gas cooler(test section). The test section consists of a smooth, horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $400\;kg/m^{2}s$ and the inlet cooling pressure of 7.5 MPa to 10.0 MPa. The variation of heat transfer coefficient tends to decrease as cooling pressure of $CO_2$ increases. The heat transfer coefficient with respect to mass flux increases as mass flux increases. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with that predicted by Blasius's correlation. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Bringer-Smith.

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초임계상태 이산화탄소의 정사각 단면 직덕트 내 난류유동 및 열전달의 전산해석 (Numerical Analysis of Turbulent Carbon Dioxide Flow and Heat Transfer under Supercritical State in a Straight Duct with a Square Cross-Section)

  • 최영돈;주광섭;김용찬;김민수
    • 설비공학논문집
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    • 제14권12호
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    • pp.1004-1013
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    • 2002

  • Turbulent carbon dioxide flows and cooling heat transfers under supercritical state in a straight duct with a square cross-section are numerically analyzed employing low Reynolds number $\kappa-\varepsilon$ model and algebraic stress model. The flow is assumed to be (quasi-incompressible. Predicted Nusselt number and friction factor are compared with the experimental data, Blasius correlation for friction factor and Dittus-Boelter correlation for Nusselt number. Computational results for the Fanning's friction factor agree well with the all Rohsenow and Choi's correlation, Liou and Hwang's experimental data and Blasius correlation. The results obtained by algebraic stress model agree more with the Liou and Hwang's experimental data, while the results obtained by low Reynolds number $\kappa-\varepsilon$ model agree more with Blasius correlation. In the computation of Nusselt number, Dittus-Boelter correlation can not exactly fit the computational results. Therefore we propose the new correlation$Nu=0.053Re^{0.73}Pr^{0.4}$for the turbulent cooling heat transfer of carbon dioxide under supercritical state.

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초임계 이산화탄소의 수직 상향 유동에서의 관내 열전달에 관한 실험적 연구 (Experimental Investigation of Heat Transfer During Vertical Upward Flow of Supercritical CO2 in Circular Tube)

  • 김동억
    • 대한기계학회논문집B
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    • 제38권7호
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    • pp.607-618
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    • 2014

  • 초임계 $CO_2$의 수직상향유동에서의 난류열전달에 관한 실험적연구가 내경 4.5 mm의 원형관에서 수행되었다. 실험범위는 유체평균온도 $29-115^{\circ}C$, 압력 74.6 - 102.6 bar, 국부 벽면 열유속 $38-234kW/m^2$ 그리고 질량유속 $208-874kg/m^2s$였다. 중간정도의 벽면 열유속 및 낮은 질량유속에서 벽면온도는 확연한 최대점을 나타냈다. 열전달에 대한 부력 및 유동가속의 영향을 살펴보기 위하여 실험 및 참조상관식(Kranoshchekov and Protopopov)에서 획득된 Nusselt 수의 비를 부력 및 유동가속을 나타내는 변수인 $Bo^*$ 및 $q^+$를 이용하여 분석하였다. 이 분석을 통해 유동가속 변수인 $q^+$는 실험에서의 열전달 현상을 적절히 표현할 수 있는 변수라는 것을 확인할 수 있었다. 마지막으로 초임계 유체의 수직상향 유동에서의 새로운 열전달 상관식이 개발되었으며, 이 상관식은 ${\pm}30%$의 오차범위에서 실험데이터를 잘 예측하였다.

  • https://doi.org/10.3795/KSME-B.2014.38.7.607 인용 PDF KSCI