• 설비공학논문집
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• 제15권10호
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• pp.795-801
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• 2003

The primary object of this study is to obtain a basic knowledge of heat transfer enhancement mechanism as affected by temperature driven Marangoni convection. Experiments is achieved to visualize the enhanced heat transfer phenomena by the effect of Marangoni convection through the laser holographic interferometry. Also Nusselt Number is introduced for the relation of Marangoni Number.

• 설비공학논문집
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• 제8권4호
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• pp.510-518
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• 1996

The study presents experimental and theoretical analysis focusing on the infulence of a noncondensable gas upon the absorption enhancement that is obtained by Marangoni convection generated by the addition of the surfactant. The shadowgraph method is adopted in this visualization. As a result of absorption phenomena with shadowgraph photos, the different patterns of Marangoni convection cells are observed in accordance with the various amounts of noncondensable gas. Furthermore, non dimensional number K(Ma/Ra) is introduced to calculate the value of surface tension difference theoretically for the comparison with the various amount of non condensable gas in absorber.

• 설비공학논문집
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• 제4권2호
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• pp.65-71
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• 1992

In most absorption machines, absorption enhancement has been achieved by adding small amount of surfactant additive, which introduced the surface tension difference between absorbent and surfactant droplets in the vapor absorption. The aim of this study is to understand a basic mechanism of Marangoni convection and its effectiveness in the vapor absorption enhancement. In this study, nonflowing aqueous solution of LiBr 60 mass% was exposed to saturated water vapor under the condition that two dropwises surfactant were fixed on the absorbent surface. Our experiments achieved to visualize the enhanced heat and mass transfer phenomena by the effect of Marangoni convection through the laser holographic interferometry. Also, Marangoni convection behavior was obtained by using tracer method.

• 설비공학논문집
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• 제14권6호
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• pp.450-455
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• 2002

Convective instability driven by surface tension is analyzed in an initially quiescent water absorbing ammonia gas using the linear stability theory. The propagation theory is adapated to find the critical conditions of the onset of solutal Maragoni convection. In this theory, the solutal penetration depth is chosen as the length scale factor. The results show that the liquid layer becomes more stable with decreasing the Schmidt number It is interesting that for a smaller Biot number than 100, the system becomes stable with decreasing Bi but for a larger Bi, it becomes unstable with decreasing Bi.

• 설비공학논문집
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• 제15권11호
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• pp.964-969
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• 2003

The objective of this study is to investigate the effect of surfactant on the onset of Marangoni convection adapting a non-linear surface equation of state. The surface tension gradient with respect to the absorbate concentration, ${\gamma}$, is linearly related to the surface concentration of a surfactant with a coeffcient $x_{A}$. The numerical results show that the role of the initial surfactant concentration to Marangoni instability changes from the stabilizer to the destabilizer depending on the change of the sign of $x_{A}$ from negative to positive. It is concluded that for $x_{A}$>0 there is a critical modified Marangoni number of surfactant $M_{Ac}$ $^{*}$ above which liquid layer is always unstable against long wave disturbances.rbances.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.78.1-78.1
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• 2005

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2003년도 하계학술대회 논문집
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• pp.140-140
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• 2003

• 한국분무공학회지
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• 제26권2호
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• pp.67-72
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• 2021

Rayleigh-Benard-Marangoni (RBM) convection have been artificially made for application of various engineering fields. For a relatively larger circular container, natural convection experiments were carried out to reveal and show the flow characteristics with engine oil (SAE30) using IR camera. IR camera has captured the temperature distribution on the free surface. From these experiments, it was confirmed that it was possible to quantitatively analyze the occurrence characteristics of RBM flow clearly from the thermal images taken with IR camera. As the aspect ratio increased, both the number of internal and external cavities increased. And found that the criteria of RBM flow generation proposed through previous experiments performed for small-sized containers are also very effective with the results on larger circular container.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1202-1209
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• 2004

In this study, numerical investigation has been performed on the evolution of weld pool geometry with moving free surface during low-energy density laser welding process. The free surface elevates near the weld pool edge and descends at the center of the weld pool if d$\sigma$/dT is dominantly negative. It is shown that the predicted weld pool width and depth with moving free surface are a little greater than those with flat weld pool surface. It is also believed that the weld pool surface oscillation during the melting process augments convective heat transfer rate in the weld pool. The present analysis with moving free surface should be considered when We number is very small compared to 1.0 since the deformation of the weld pool surface is noticeable as We number decreases.

• 대한기계학회논문집B
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• 제29권10호
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• pp.1111-1118
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• 2005

In this study, a unified numerical investigation has been performed on the evolution of weld pool and key-hole geometry during low-power and high-power density laser welding. Unsteady phase-change heat transfer and fluid flow with the surface tension are examined. The one-dimensional vaporization model is introduced to model the overheated surface temperature and recoil pressure during high-power density laser welding. It is shown that Marangoni convection in the weld pool is dominant at low-power density laser welding, and the keyhole with thin liquid layer and the hump are visible at high-power density laser welding. It is also shown that the transition from conduction welding to penetration welding fur iron plate exists when the laser power density is about $10^6W/Cm^2$.