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불균일 핵형성에 관한 연구: n-Hexadecane 표면 위에서 수증기의 응축

A Study on Heterogeneous Nucleation: The Condensation of Water Vapor on n-Hexadecane

송요순^† JosephL.Katz

Yo Soon Song^† Joseph L. Katz¹

전남대학교 공과대학 응용화학부, 광주 500-757

Faculty of Applied Chemistry, Chonnam National University, Kwangju 500-757, Korea ¹Department of Chemical Engineering, The Johnes Hopkins University, Baltimore, Maryland 21218, USA

HWAHAK KONGHAK, February 2002, 40(1), 34-42(9), NONE

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Abstract

고체 위에 응축이 시작되는 불균일 핵형성에 고전적인 식으로 알려진 Volmer식을 n-hexadecane 액상 위에 수증기가 응축하는 계에 적용하였다. 액상 표면에서 Volmer 식을 새롭게 해석하고 thermal diffusion cloud chamber를 이용하여 n-hexadecane 표면 위에 물이 응축하는 불균일 핵형성에 대한 실험을 수행하였다. 관찰된 임계과포화도는 Volmer 식으로 계산된 임계과포화도보다 작았다. 또한 분자 운동론에 의해 유도된 불균일 핵형성 속도식은 Volmer 식에서 구한 값과 같았다. 실험에서 구한 임계 과포화 값이 이론값으로부터 편이 되는 이유는 계면장력의 거시적 물성값이 핵형성이 일어나는 미시적 상태의 물성값과 달라질 수 있다고 생각하였다. 한편 임계 과포화에 대한 정의가 실험값과 이론값이 다르기 때문에 두 값은 차이가 날 수 있다고 생각하였다.

The classical Volmer’s theory of heterogeneous nucleation on solid surfaces was applied to a condensing system of water vapor on n-hexadecane liquid surface. The Volmer’s equation was newly analyzed in the case of liquid surface and an experiment was carried out to study the condensation of water vapor on the surface of n-hexadecane in a thermal diffusion cloud chamber. The observed critical supersaturation was smaller than the theoretical value calculated from the Volmer’s theory. And the critical supersaturation predicted by a kinetic theory was found to be equal to that by the Volmer's equation. The discrepancy of critical supersaturation between experimental and theoretical values probably stemmed from the difference in the value of interfacial tensions between macroscopic and microscopic states. Also this discrepancy seemed to be reasonable since the theoretical and empirical definitions of the critical supersaturation were different.

Keywords

Heterogeneous Nucleation Thermal Diffusion Cloud Chamber Supersaturation Volmer Equation

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