• Journal of Mechanical Science and Technology
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• 제14권12호
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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.

• 대한기계학회논문집B
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• 제29권7호
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• pp.846-853
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• 2005

In this paper, mass transfer in turbulent flow around a rotating circular cylinder is investigated by Direct Numerical Simulation for Schmidt numbers Sc=1 and 1670. Correlation between Sherwood and Reynolds number predicted agrees well with other experimental results over both Sc. Reynolds analogy identified at Sc=1 definitely causes a strong correlation between concentration fluctuation and streamwise velocity. For Sc=1670, it is found that positive small values of concentration fluctuations are observed more frequently than the case of Sc=1 particularly out of the range of Nernst diffusion layer in the viscous sub-layer. This fact is fully confirmed by detailed statistical study using a probability density function of concentration fluctuations.

• 대한기계학회논문집
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• 제14권3호
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• pp.685-693
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• 1990

본 연구에서는 복사열전달 효과를 알아보기 위해 에너지 방정식을 수치적으로 풀었으며, 그 결과를 열전달계수 및 온도의 항으로 나타내었다. 수치 해석적 모델의 검증을 위해 여러사람들이 물질전달과정 해석을 위해 사용한 나프타린 승화법(naphth- alene sublimation technique)을 이용하여 실험을 수행하였다. 또한 실험에 사용된 다공질체(ceramic blocks)의 침투율도 측정하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제23권3호
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• pp.157-178
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• 2019

The present correspondence is conveyed on to consider the fascinating and novel characteristics of radiative hydromagnetic convective flow of a chemically reacting fluid over an exponentially accelerated inclined porous plate. Exact solutions for the fluid velocity, temperature and species concentration, under Boussinesq approximation, are obtained in closed form by the two term perturbation technique. The interesting parts of thermal dispersing outcomes are accounted in this correspondence. Graphical evaluation is appeared to depict the trademark direct of introduced parameters on non dimensional velocity, temperature and concentration profiles. Also, the numerical assortment for skin friction coefficient, Nusselt number and Sherwood number is examined through tables. The certification of current examination is confirmed by making an examination with past revelations available in composing, which sets a benchmark for utilization of computational approach.

• Journal of Magnetics
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• 제21권3호
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• pp.476-489
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• 2016

In the present study, squeezing flow of micropolar nanofluid between parallel infinite disks in the presence of magnetic field perpendicular to plane of the disks is taken into account. The constitutive equations that govern the flow configuration are converted into nonlinear ordinary differential with the help of suitable similarity transforms. HAM package BVPh2.0 has been employed to solve the nonlinear system of ordinary differential equations. Effects of different emerging parameters like micropolar parameter K, squeezed Reynolds number R, Hartmann number M, Brownian motion parameter Nb, thermophoresis parameter Nt, Lewis number Le for dimensionless velocities, temperature distribution and concentration profile are also discussed graphically. In the presence of strong and weak interaction (i.e. n = 0 and n = 0.5), numerical values of skin friction coefficient, wall stress coefficient, local Nusselt number and local Sherwood number are presented in tabulated form. To check the validity and reliability of the developed algorithm BVPh2.0 a numerical investigation is also a part of this study.

• 대한기계학회논문집B
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• 제37권3호
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• pp.285-292
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• 2013

본 연구의 목적은 평판의 선단에 설치된 트리핑 와이어에 의한 경계층 박리가 층류에서 난류로의 천이에 미치는 영향과 그 결과로 발생하는 물질전달에 미치는 영향을 규명하는 것이다. 나프탈렌승화법을 사용하여 평판에서의 국소물질전달계수를 측정하였으며, 유동 경계층의 효과를 평가하기 위해 발달된 유동과 발달하는 유동의 조건에서 트리핑 와이어가 설치된 평판에서의 국소물질전달계수를 설치되지 않은 평판에서의 값과 비교하였다. 발달하는 유동에서 국소물질전달계수가 변화하는 경향은 트리핑 와이어가 설치된 평판과 설치되지 않은 평판이 비슷하지만 발달된 유동에서는 상당히 다르게 나타났다. 평균 Sherwood 수는 경계층 박리로 인하여 트리핑와이어가 설치된 평판이 설치되지 않은 평판에 비해서 훨씬 높았다.

• Journal of Magnetics
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• 제21권3호
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• pp.468-475
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• 2016

In this article, entropy generation on MHD Williamson nanofluid over a porous shrinking sheet has been analyzed. Nonlinear thermal radiation and chemical reaction effects are also taken into account with the help of energy and concentration equation. The fluid is electrically conducting by an external applied magnetic field while the induced magnetic field is assumed to be negligible due to small magnetic Reynolds number. The governing equations are first converted into the dimensionless expression with the help of similarity transformation variables. The solution of the highly nonlinear coupled ordinary differential equation has been obtained with the combination of Successive linearization method (SLM) and Chebyshev spectral collocation method. Influence of all the emerging parameters on entropy profile, temperature profile and concentration profile are plotted and discussed. Nusselt number and Sherwood number are also computed and analyzed. It is observed that entropy profile increases for all the physical parameters. Moreover, it is found that when the fluid depicts non-Newtonian (Williamson fluid) behavior then it causes reduction in the velocity of fluid, however, non-Newtonian behavior enhances the temperature and nanoparticle concentration profile.

• 대한기계학회논문집
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• 제15권5호
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• pp.1756-1762
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• 1991

본 연구에서는 막냉각되는 터빈블레이드에서의 열전달 계수를 측정하기 위하 여 열전달과 물질전달의 상사관계를 이용하였다.터빈블레이드의 선단을 다른 연구 에서와 마찬가지로 원봉으로 모사하였고, 원봉의 표면에 위치하고 있는 1열의 분사홀 로부터 제트가 분사될 때 분사홀 근처 및 그 하류에서의 물질 전달계수를 측정하기 위 해 나프탈렌승화법을 이용하였다. 분사홀 열의 위치를 정체점에서 하류방향으로 이 동시키면서, 물질전달계수의 변화를 연구하였고, 분사율(M=.rho.$_{j}$ U$_{j}$ /.rho.$_{\infty}$ U$_{\infty}$)의 영향도 고찰하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권3호
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• pp.203-224
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• 2016

The heat and mass transfer characteristics of the unsteady hydromagnetic natural convection flow with Hall current and Soret effect of an incompressible, viscous, electrically conducting, heat absorbing and optically thin radiating fluid flow past a suddenly started vertical infinite plate through fluid saturated porous medium in a rotating environment are taken into account in this paper. Derivations of exact analytical solutions are aimed under different physical properties. The velocity, concentration and temperature profiles, Sherwood number and Nusselt number are easily examined and discussed via the closed forms obtained. Soret effect and permeability parameter tends to accelerate primary and secondary fluid velocities whereas hall current, radiation and heat absorption have reverse effect on it. Radiation and heat absorption have tendency to enhance rate of heat transfer at the plate. The results obtained here may be further used to verify the validity of obtained numerical solutions for more complicated transient free convection fluid flow problems.

• 대한기계학회논문집B
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• 제27권5호
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• pp.604-611
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• 2003

This study was concerned with the enhancement of mass transfer by surfactant added to the aqueous solution of LiBr. Different vertical inner tubes were tested with and without an additive of normal octyl alcohol. The test tubes were a bare tube, groove tube, corrugate tube and inserted spring tubes. The additive concentration of normal octyl alcohol as a surfactant is about 0.08mass%. The Sherwood number was measured as a function of film Reynolds number 20~200. The experimental results were compared with those which use no surfactant. The enhancement of mass transfer by Marangoni convection effect which was generated by addition of the surfactant is proved for each testing tube Especially, it is clarified that the tube with the spring has the highest enhancement effect. A correlation of the experimental mass transfer data for the bare, groove, corrugate and insert spring tubes results expressed as the form of Sh=cㆍ Re$_{f}$ $^{n}$ .