• Journal of applied mathematics & informatics
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• v.40 no.1_2
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• pp.99-115
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• 2022

The problem of Benard double diffusive Marangoni convection is investigated in a horizontally infinite composite layer system consisting of a two component fluid layer above a porous layer saturated with the same fluid, using Darcy-Brinkman model with constant heat sources/sink in both the layers. The lower boundary of the porous region is rigid and upper boundary of the fluid region is free with Marangoni effects. The system of ordinary differential equations obtained after normal mode analysis is solved in closed form for the eigenvalue, thermal Marangoni number for two types of thermal boundary combinations, Type (I) Adiabatic-Adiabatic and Type (II) Adiabatic -Isothermal. The corresponding two thermal Marangoni numbers are obtained and the essence of the different parameters on non-Darcy-Benard double diffusive Marangoni convection are investigated in detail.

• Journal of the Korean Electrochemical Society
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• v.3 no.3
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• pp.136-140
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• 2000

A stainless steel separator for a molten carbonate fuel cell is usually coated with aluminum diffusive layer to protect its surface against corrosion by the molten carbonate at high temperatures. In this study, a relatively simple method was devised to form the aluminum diffusive layer on a stainless steel substrate. Slurry coating of aluminum on the substrate followed by heat treatment under reducing atmosphere at $650\~800^{\circ}C$ produced the aluminum diffusive layer of $25\~80{\mu}m$ thickness. The thickness of aluminum diffusive layer increased with increasing the temperature or duration of the heat-treatment. The corrosion resistance against molten carbonate under oxidizing atmosphere was significantly improved by aluminum diffusive layer formed by the sluny painting and heat treatment method. Moreover, the sample prepared in this study showed corrosion behavior similar to the sample with aluminum diffusive layer prepared by ion vapor deposition and heat treatment.

• Solar Energy
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• v.6 no.2
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• pp.15-21
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• 1986

In this study, an experimental double diffusive thermohaline system heated from below was constructed and the phenomena of each layer developed in the system were observed. The experiment was performed with the initial salt concentration gradient of $-436.2kg/m^4$ and the net heat flux of approximately $176w/m^2$. An electroconductivity-temperature probe was made and used for the measurements of salt concentration. As the result of this study, it was found that the salt concentration decreased in the bottom mixed layer and increased in the top mixed layer during the experiment while the salt concentration gradient in the diffusive layer unchanged. It was also found that the interfacial boundary layers were due largely to variations in salt concentration rather than temperature.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.53-54
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• 2002

New lubrication mechanism for nanomachine is proposed. This mechanism utilizes the effect of diffusive double layer observed in hydrophobic colloidal solution. Basic idea of the theory is inspired by the research for possible mechanism of bacterial flagellar motor In this study, formulation of this mechanism is achieved and numerical calculation is performed. It is shown that this mechanism can produce enough load capacitance. Furthermore not only capacitance to sustain driving force of flagellar motor

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3297-3304
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• 1994

Experimental investigation have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution heated from below in a cylindrical cavity. The objective is to examine the process of mixed-layer formation, the flow phenomena, the heat transfer characteristics, and temperature and concentration distribution according to the changes in the effective Rayleigh number based on the reference height which represents the relation of temperature and concentration gradient. The types of initially formed flow pattern are categorized in three regimes depending on the effective Rayleigh number ; stagnant flow regime, single mixed-layer flow regime and successively formed multiple mixed-layer flow regime. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered flow regime, but both linear in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly. The layers expand by diffusion of concentration through the interface along with its random fluctuation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1731-1740
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• 1995

Experimental investigations have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution due to heating from below in a rotating cylindrical cavity. The objective is to examine the flow phenomena and the heat transfer characteristics according to the changes in temperature gradient, concentration gradient and rotating velocity of cavity. Thermal and solutal boundary conditions at side wall are adiabatic and impermeable, respectively. The top and bottom plate are maintained each at constant temperature and concentration. The cavity is put into a state of solid body rotation. Like the stationary case, the types of initially-formed flow pattern are classified into three regimes depending on the effective Rayleigh number and Taylor number; stagnant flow regime, single mixed-layer flow regime and successively formed multi-mixed layer flow regime. At the same effective Rayleigh number, the number of initially-formed mixed layer and its growth rate decrease as the effect of rotation increases. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered-flow regime, but look both liner in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly.

• Journal of Mechanical Science and Technology
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• v.14 no.12
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• pp.1396-1402
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• 2000

Here is investigated the characteristics of double-diffusive convection in thermally-stable stratified horizontal fluid layer. By employing an electrochemical technique, and adopting aqueous CuSO$_4$-H$_2$SO$_4$solution as electrolyte, experiments on ionic mass transfer have been conducted systematically. And, also a new mass transfer correlation in double-diffusive situations has been derived by extending the model of micro-scales of turbulence, which was proposed by Arpaci. The resulting correlation of the Sherwood number as a function of the thermal Rayleigh number was in good agreement with the present experimental results. The present study provides plausible understanding in controlling both mass and heat transfer rates for practical situations including double-diffusive convection.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.304-313
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• 1987

The behaviors of layers developed in a solar pond were studied by experimental and analytical methods. An experimental solar pond heated from below was constructed and operated at the net heat fluxes of 110 and 160W/m$^{2}$ and at the initial salt concentration gradients of 18.2, 27.3 and 36.4%/m. The thicknesses, growth rates, temperature and salt concentration in the top and the bottom mixed layers, the diffusive layer and the upper and the lower interfacial boundary layers were measured. The shadowgraph technique was used in order to observe all layer formation and an electroconductivity-temperature probe consisting of four electrodes was fabricated and used in measuring the salt concentration. Based on the experimental results, a model for the solar pond was developed and the governing equation and the assumptions were established. The governing equations were solved by the numerical method. The calculated results obtained from the analysis were compared with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1720-1730
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• 1995

Finite-difference analysis was conducted to study the natural convection of a stably stratified salt-water solution in an annulus due to lateral heating. The main purpose of this study is to examine in detail the multi-layered flow structure. Calculation was thus made for R $a_{\eta}$=2*10$^{5}$ and 6.5*10$^{5}$ . Formation of layered flow structure, merging process of layers, the corresponding temperature and concentration distributions, Nusselt number variations with time are examined. Numerical results show that in each layer, the temperature profile looks 'S`-shaped and the concentration profile is uniform due to the convective mixing. The formation of the roll and the layer is governed by natural convection due to the temperature gradient and the merging process of the layer by diffusion of the concentration.ation.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.6
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• pp.606-612
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• 1987

In this study, numerical model was developed to predict behavior of several layers in a solar pond and was solved by finite difference method. The empirical correlation that described heat and salt fluxes across interfacial boundary layer between mixed layer and diffusive layer in a solar pond were obtained from experiments and utilized in developing numerical model. As the results of this study, heat and salt fluxes across the interfacial boundary layer was found to depend on density ratio ${\beta}{\Delta}M_s/{\alpha}{\Delta}T.$ It was also found that the predicted value obtained by using the modified Weinberger's stability criteria showed a good agreement with experiment data.