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비등온,비단열 고정층반응기에서의 열전달계수 산출
Determination of Heat Transfer Coefficients in a Nonisothermal and Nonadiabatic Fixed-bed Reactor
HWAHAK KONGHAK, June 1996, 34(3), 312-320(9), NONE
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Abstract
유체가 흐르고 있는 정상상태의 비등온 비단열 고정촉매층에서 내부와 장치기벽 여러 지점 온도를 측정하여 고정촉매층의 열전달계수 및 유효열전도도를 최적계수산출법으로 구하는 방법을 제시하였다. 열전달현상을 1차원 및 2차원 균일모델로 해석하고 1차원모델에서는 총괄열전달계수(ht)를, 2차원모델에서는 유효열전도도(ker)와 내부벽면열전달계수(hw)를 구하였다. 직경 4인치 반응기에서 내부의 온도분포가 200-300℃일 때 산출된 열전달계수들(ht, ker, hw)이 반응기를 가열하는 경우와 냉가시키는 경우에 각각 다르게 나타났다. 산출된 유효열전도 ker은 촉매층 내부에서의 대류효과를 포함한 수치이며 냉각 및 가열에 의한 대류현상이 유효열전도도에 미치는 영향에 대해 검토하였다. 산출된 계수들을 이용하여 계산된 반응기내 온도분포는 실측치와 매우 잘 일치하였다. 본 연구에서 사용된 방법은 열전달계수 및 유효열전도도를 측정하기 위한 별도의 실험장치없이, 실제공장의 반응기에서 반응이 억제되는 조건으로 운전하면서 온도를 측정하여 이 값들을 산출할 수 있는 장점이 있다.
Amethod for determining heat transfer coefficients and the effective thermal conductivity in a nonisothermal and nonadiabatic fixed-bed reactor has been proposed. By using the temperatures experimentally measured at several points in the fixed-bed and the outside wall of the reactor, the overall heat transfer coefficient(ht), the inside wall heat transfer coefficient(hw), and the effective thermal conductivity(ker) were calculated on the assumption that the system is pseudo-homo-geneous. The system has been analyzed one-dimensionally for ht and two-dimensionally for hw & ker, respectively. The coefficients obtained in the temperature range of 200-300℃ for the reactor of 4" diameter were found to be different for heating or cooling. Nevertheless, the temperature distributions in the reactor simulated with the obtained coefficients were in a good accordance with the experimental observations. The effect of fluid convection in the fixed-bed according to heating or cooling on ker was also discussed. The method proposed in this study can be very effectively used in determining the coefficients and predicting the temperature distribution in an industrial fixed-bed reactor without any additional system or instrument.
Keywords
References
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Herskowitz M, Hagan PS, AIChE J., 34, 1367 (1988)
Paterson WR, Carberry JJ, Chem. Eng. Sci., 38, 175 (1983)
Valstar JM, VandenBerg PJ, Oyserman J, Chem. Eng. Sci., 30, 723 (1975)
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Tarhan MO, "Catalytic Reactor Design," McGraw-Hill Book Co, New York (1983)
Ahmed M, Fahien RW, Chem. Eng. Sci., 35, 889 (1980)
Dixon AG, AIChE J., 31, 826 (1985)
Yage S, Kunii D, AIChE J., 3, 373 (1957)
Yage S, Kunii D, AIChE J., 6, 97 (1960)
Schlunder EU, Chem. Eng. Technol., 43, 651 (1971)
Zehner P, Schlunder EU, Chem. Eng. Technol., 44, 1303 (1972)
Dixon AG, Cresswell DL, AIChE J., 25, 663 (1979)
Coberly CA, Marshall WR, Chem. Eng. Prog., 47, 141 (1951)
Bhattacharyya CA, Pei DCT, Chem. Eng. Sci., 30, 293 (1975)
Wakao N, Kaguei S, "Heat and Mass Transfer in Packed Beds," Gorden and Breach Science Pub., New York (1982)
Balakrishnan AR, Pei CT, Ind. Eng. Chem. Process Des. Dev., 18, 31 (1979)
Plautz DA, Johnstone HF, AIChE J., 1, 193 (1955)
Hanrattry TJ, Chem. Eng. Sci., 5, 209 (1954)
Hougen JO, Piret EL, Chem. Eng. Prog., 47, 295 (1951)
Wakao N, Kato K, J. Chem. Eng. Jpn., 2, 24 (1969)
deBoor C, "A Practical Guide to Splines," Springer-Verlag, New York (1978)
