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균일 기체 유동 속의 물방울의 증발에 복사열전달이 미치는 영향
The Effects of the Radiative Heat Transfer on the Water Droplet Evaporation in Uniform Gaseous Flow
HWAHAK KONGHAK, August 1998, 36(4), 607-617(11), NONE
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Abstract
본 연구에서는 수치모사를 통하여 고온 균일 기체 흐름 속의 물방울에 대하여 증발현상을 고찰하였다. 기존의 연구에서는 액적의 증발에 복사가 미치는 영향을 고려하지 않거나 액적의 증발없이 복사 열전달에 의한 내부 열발생랑만을 계산하였다. 고온 환경 속의 액적이 받는 복사열은 주로 적외선이므로 액적의 크기와 유사한 파장을 갖는다. 따라서 적외선은 액적 내부로 침투하여 액적 내부에서 열을 발생시킨다. 본 연구에서는 Mie의 해를 써서 열발생량을 구하여 액적 내부 및 외부의 유체 유동과 물질전달, 열전달을 포괄하여 동시에 풀었다. 수치모사가 올바르게 수행되었는지 검증하기 위하여 정상상태에서의 항력계수와 Nusselt 수, Sherwood 수를 수치적으로 구하여 실험으로부터 얻은 상관식과 매우 잘 일치함을 보여 주었다. 액적의 증발에 복사가 미치는 효과를 고찰하기 위하여 초기온도가 300 K인 물방울과 1,300 K, 1,900 K인 공기를 사용하여 Nusselt 수와 Sherwood 수를 계산하였다. 주위 기상의 온도가 상승할수록 복사로 인해 발생하는 열량이 증가하였다. 그러나 물방울의 경우에 굴절률의 허수부가 매우 작기 때문에 복사가 물방울의 내부유동이나 기-액 전달현상, 증발 등에 미치는 영향은 거의 없었다.
The phenomenon of water droplet evaporation in hot gaseous flow is investigated numerically in the present study. In the past researches the effects of radiation on the droplet evaporation have not been taken into consideration or only the internal heat generation due to radiation was calculated without considering the droplet evaporation. Since the infrared light, which the droplet in hot environments is subject to, has a wavelength range comparable to the droplet size, the light transverses to heat generated in the droplet. By employing the Mie solution to obtain heat generation inside the droplet, the fluid flow, the heat transfer and the mass transfer inside and outside the droplet are calculated simultaneously. To prove that the numerical algorithm has been correctly applied, the drag coefficient, the Nusselt number and the Sherwood number calculated numerically at steady state are shown to agree well with experimental correlations. To find out the effects of radiation on the droplet evaporation, the water drop at the initial temperature of 300 K and the air of 1,300 K or 1,900 K are employed for case study, and Nuf and Shf are calculated. The higher the gas phase temperature is, the more heat generation occurred inside the droplet. The radiation, however, made no influence on the flow pattern inside the droplet, the transport phenomena, the evaporation, etc., since the imaginary part of the refractive index for water is very small, resulting in negligible heat generation.
References
Law CK, Combust. Flame, 29, 175 (1977)
Patnaik G, Ph.D. Dissertation, Carnegie-Mellon Univ., U.S.A. (1986)
Chiang CH, Raju MS, Sirignano WA, Int. J. Heat Mass Transf., 35, 1307 (1969)
Sitarski M, Combust. Sci. Technol., 54, 177 (1987)
Ranz WE, Marshall WR, Chem. Eng. Prog., 48, 141 (1952)
Haywood RJ, Nafziger R, Renkiszbulut M, J. Heat Transf., 111, 495 (1989)
Renkiszbulut M, Nafziger R, Li X, Chem. Eng. Sci., 46, 2351 (1991)
Hoffman KA, "Computational Fluid Dynamics for Engineers," A Publication of Engineering System, Wichita, Kansas (1993)
Patankar SV, "Numerical Heat Transfer and Fluid Flow," Hemisphere Publishing Corporation, London (1980)
Sadhal SS, Ayyaswamy PS, Chung JN, "Transport Phenomena with Drops and Bubbles," Springer-Verlag, New York (1997)
Abramzon B, Sirignano WA, Int. J. Heat Mass Transf., 32, 1605 (1989)
Sundararajan T, Ayyaswamy PS, J. Fluid Mech., 149, 33 (1984)
Patnaik G, Ph.D. Dissertation, Carnegie-Mellon Univ., U.S.A. (1986)
Chiang CH, Raju MS, Sirignano WA, Int. J. Heat Mass Transf., 35, 1307 (1969)
Sitarski M, Combust. Sci. Technol., 54, 177 (1987)
Ranz WE, Marshall WR, Chem. Eng. Prog., 48, 141 (1952)
Haywood RJ, Nafziger R, Renkiszbulut M, J. Heat Transf., 111, 495 (1989)
Renkiszbulut M, Nafziger R, Li X, Chem. Eng. Sci., 46, 2351 (1991)
Hoffman KA, "Computational Fluid Dynamics for Engineers," A Publication of Engineering System, Wichita, Kansas (1993)
Patankar SV, "Numerical Heat Transfer and Fluid Flow," Hemisphere Publishing Corporation, London (1980)
Sadhal SS, Ayyaswamy PS, Chung JN, "Transport Phenomena with Drops and Bubbles," Springer-Verlag, New York (1997)
Abramzon B, Sirignano WA, Int. J. Heat Mass Transf., 32, 1605 (1989)
Sundararajan T, Ayyaswamy PS, J. Fluid Mech., 149, 33 (1984)
