The nucleation site density (N/A) during pool boiling of binary mixtures has been experimentally examined in terms of the heating surface physical properties, the liquid physical properties, the vapour liquid equilibria and the surface micro-roughness. The liquid mixtures used were acetone - carbon tetrachloride and n-hexane - carbon tetrachloride. A parameter Ra, to characterize the micro-roughness of the heating surface was defined as the average value of the peaks and valleys on the surface. The study shows that while at low Ra values the physical properties of the liquid and the binary composition are not as important as the surface roughness; at higher Ra values the liquid properties and composition are also important. A correlation based on the present data has been proposed.

R. J. Benjamin

Arcot R. Balakrishnan

Carbon dioxide

Crystallization

Hydrates

Methane

Reaction kinetics

solubility

CARBON DIOXIDE HYDRATE

METHANE HYDRATE

Gas hydrates

Boiling

density

MIXTURE

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Canadian Journal of Chemical Engineering

Steady state pool boiling heat flux data has been obtained for acetone-isopropanol-water and acetone- MEK(methyl ethyl ketone)-water ternary mixtures. The data shows that to obtain a given heat flux, the wall superheat required is greater for mixtures than for the pure components constituting the mixture. The measured heat transfer coefficients were compared with predictions from literature correlations for multicomponent mixtures. In all the cases, overestimation or underestimation of the data was observed. Therefore, a new correlation has been proposed for the heat flux in terms of Archimedes number, Prandtl number, surface-liquid interaction parameter, modified Jakob number, dimensionless surface roughness group, properties-profile parameter and an effective temperature driving force. In general, the effective temperature driving force in binary mixtures is less than that encountered in pure components and is obtained by incorporating the binary diffusivity of the mixture. In multicomponent systems, the multicomponent diffusion coefficients have to be incorporated into the expression for the effective temperature driving force. The heat flux correlation predicts the present experimental data as well as literature data, satisfactorily. The heat flux was found to be a function of the difference between the equilibrium vapour and liquid concentration, (y - x) of the light component(s) and the minimum heat flux occurs at the maximum of (y - x) of the light component(s).

Chemical Engineering Research and Design

Nucleate pool boiling heat transfer of multicomponent mixtures

Steady state pool boiling heat transfer coefficients have been obtained experimentally for acetone-isopropanol-water and acetone-MEK (methyl ethyl ketone)-water ternary systems. The data show that, for a given heat flux, the heat transfer coefficients of mixtures are lower than those obtained for pure components constituting the mixture. The measured heat transfer coefficients were compared with predictions from literature correlations for pool boiling of multicomponent mixtures. In all the cases, overestimation or underestimation of the data was observed. The literature correlations incorporate an 'ideal' heat transfer coefficient and a correction term for the presence of other liquids. Part of the uncertainty associated with the literature correlations on comparison with the present data appears to be due to the uncertainty in estimating the ideal heat transfer coefficient. The methods suggested by the earlier authors found to be not applicable for the present heating surface-liquid combinations. Therefore, in the present study, two different correlations were tried for the ideal heat transfer coefficient and it was found that the performance of the literature correlations improved considerably. However, the methods reported in the literature and the correlations tried in the present study to estimate ideal heat transfer coefficient did not consider heating surface-liquid interaction and the effect of heating surface micro-roughness in boiling. Therefore, a correlation to estimate the ideal heat transfer coefficient has been proposed taking into account surface-liquid interaction parameter and surface roughness group. A new correlation to estimate mixture heat transfer coefficients has been proposed in the present study in terms of an ideal heat transfer coefficient and a correction term. In general, the correction term in binary mixtures is obtained by incorporating the binary diffusivity of the mixture. In multicomponent systems, the multicomponent diffusion coefficients have to be incorporated in the expression for the correction term. The mixture heat transfer coefficient correlation along with the correlation for ideal heat transfer coefficient proposed in the present study predicts the present experimental data as well as literature data satisfactorily. The heat transfer coefficient was found to be a function of the difference between the equilibrium vapor and liquid concentration of the light component(s) and the minimum heat transfer coefficient occurs at the maximum of this value. © 2004 Elsevier Inc. All rights reserved.

Experimental Thermal and Fluid Science

Heat transfer in nucleate pool boiling of multicomponent mixtures

A model for nucleate pool boiling heat transfer of binary mixtures has been proposed based on an additive mechanism. The contributing modes of heat transfer are (i) the heat transferred by microlayer evaporation, (ii) the heat transferred by transient conduction during the reformation of the thermal boundary layer, and (Hi) the heat transferred by turbulent natural convection. The model takes into account the microroughness of the heating surface which has been defined quantitatively. The model compares satisfactorily with data obtained in the present study and in the literature. These data were obtained on a variety of heating surfaces such as a vertical platinum wire, a horizontal stainless steel tube and flat horizontal aluminium, and stainless steel surfaces (with various surface finishes) thereby demonstrating the validity of the model. © 1999 by ASME.

Fulltext

Journal of Heat Transfer

Nucleate boiling heat transfer of binary mixtures at low to moderate heat fluxes

A model based on an additive mechanism of heat transfer is proposed for pool boiling of single component systems. The contributing modes of heat transfer are: (i) the heat transferred as latent heat to the evaporating microlayer, (ii) the heat transferred by transient conduction during re-formation of the thermal boundary layer and (iii) the heat transferred by turbulent natural convection from the heating surface not influenced by the bubbles. The heat flux due to the evaporating microlayer is estimated from the instantaneous microlayer thickness during the bubble growth period. An estimate of the nucleation site density is obtained from a literature correlation that includes the boiling surface characteristics. Experimental data from the literature and the present study show very good agreement with the model, validating the postulated mechanism. Copyright © 1996 Elsevier Science Ltd.

International Journal of Heat and Mass Transfer

Nucleate pool boiling heat transfer of pure liquids at low to moderate heat fluxes

An experimental investigation on the nucleation density during nucleate pool boiling of saturated pure liquids at low to moderate heat fluxes is described. The surface-liquid interaction during the boiling phenomena and its effect on the nucleation site density and thereby the heat flux is examined. Stainless steel and aluminum with different surface finishes obtained by polishing the surfaces with different grades of emery paper was used in the study. A parameter, Ra, called the arithmetic average roughness or the centerline average was used to characterize the surface micro-roughness. The parameter Ra is defined as the average values of the peaks and valleys on the surface. This was measured experimentally by using a profilometer. The liquids used in the study were distilled water, carbon tetrachloride, n-hexane, and acetone. The nucleation site density at different heat fluxes for various surface-liquid combinations was measured by using high-speed photography. The data showed that the nucleation site density depends on the surface microroughness, the surface tension of the liquid, the thermophysical properties of the heating surface and the liquid, and the wall superheat. A correlation in terms of the wall superheat, the Prandtl number, a surface-liquid interaction parameter (the ratio of the thermal conductivity, density, and specific heat of the solid to the liquid), and a dimensionless surface roughness parameter has been proposed. The correlation proposed matches data obtained in the present study. The correlation also matches data in the literature obtained on copper and nickel surfaces of various surface finishes, further validating the correlation and the mechanism suggested in this study. © Elsevier Science Inc., 1997.

Nucleation Site Density in Pool Boiling of Saturated Pure Liquids: Effect of Surface Microroughness and Surface and Liquid Physical Properties

Monolithic Phase-Locked Loops and Clock Recovery Circuits

Theory of AFC SynchronizationDecimal classification: R583.5. Original manuscript received by the Institute, August 21, 1952; revised manuscript received February 25, 1953.

Who Was Who

Orowan, Egon, (2 Aug. 1902–3 Aug. 1989), Professor of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA, 1950–67, now Emeritus; Senior Lecturer, MIT, 1967–73

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING: Contents

Nucleation Site Density in Pool Boiling of Binary Mixtures: Effect of Surface Micro-roughness and Surface and Liquid Physical Properties

Journal	Canadian Journal of Chemical Engineering
Publisher	Canadian Society for Chemical Engineering
ISSN	00084034
Open Access	No