• Title/Summary/Keyword: Marangoni Effect

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A study of Heat Transfer Enhancement by Temperature Driven Marangoni Convection (온도차 마랑고니 대류에 의한 열전달 촉진에 관한 연구)

  • 김종윤;이동호;박종화;최국광
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.10
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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.

Visualization of Marangoni Convection Behavior between Two Surfactant Dropwises in the Process of Steam Absorption (증기흡수시(蒸氣吸收時) 계면활성제액적간(界面活性劑液滴間)에 발생(發生)하는 마랑고니대류거동(對流擧動)의 가시화(可視化))

  • Rie, D.H.;Choi, K.K.;Kashiwagi, T.;Seo, J.Y.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.4 no.2
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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.

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Onset of Marangoni Convection in a Ternary Mixture with Surfactant (계면활성제가 포함된 삼성분계 해석을 통한 마란고니 대류 발생 연구)

  • 김제익;강용태;최창균
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.11
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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.

Study of the Internal Flow and Evaporation Characteristic Inside a Water Droplet on a Vertical Vibrating Hydrophobic Surface (수직 진동을 이용한 가열된 고체표면 위 증발하는 액적의 내부유동 제어연구)

  • Park, Chang-Seok;Lim, Hee-Chang
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.1
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    • pp.37-46
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    • 2017
  • Thermal Marangoni flow has been observed inside droplets on heated surfaces, finally resulting in a coffee stain effect. This study aims to visualize and control the thermal Marangoni flow by employing periodic vertical vibration. The variations in the contact angle and internal volume of the droplet as it evaporates is observed by using a combination of continuous light and a still camera. With regard to the internal velocity, the particle image velocimetry system is applied to visualize the internal thermal Marangoni flow. In order to estimate the internal temperature gradient and surface tension on the surface of a droplet, the theoretical model based on the conduction and convection theory of heat transfer is applied. Thus, the internal velocity increases with an increase in plate temperature. The flow directions of the Marangoni and gravitational flows are opposite, and hence, it may be possible to control the coffee stain effect.

Instabilities of Natural Convection in a Shallow Fluid Layers (얇은 유체층(流體層)에 있어서 자연대류(自然對流)의 불안정성(不安定性))

  • Yang, Soong-Hyo;Park, Chan-Kuk
    • Solar Energy
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    • v.8 no.1
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    • pp.33-40
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    • 1988
  • The characteristics of thermal instabilities of natural convection in a horizontal fluid layer bounded below by a rigid plate and above by an interface with a passive gas is presented. The critical Grashof number decreases as the surface tension gradient effect (Marangoni effect) at the interface increases and the flow remains unstable for a critical Marangoni number depending on Prandtl numbers. These results are in substantial agreement with those of Smith and Davis.

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Effect of Marangoni flow on Surface Roughness and Packing Density of Inkjet-printed Alumina Film by Modulating Ink Solvent Composition

  • Jang, Hun-Woo;Kim, Ji-Hoon;Kim, Hyo-Tae;Yoon, Young-Joon;Kim, Jong-Hee;Hwang, Hae-Jin
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.99-99
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    • 2009
  • Two different micro-flows during the evaporation of ink droplets were achieved by engineering both surface tension gradient and compositional gradient across the ink droplet: (1) Coffee-ring generating flow resulting from the outward flow inside the ink droplet & (2) Marangoni flow leading to the circulation flow inside the ink droplet. The surface tension gradient and the compositional gradient in the ink droplets were tailored by mixing two different solvents with difference surface tension and boiling point. In order to create the coffee-ring generating flow (outward flow), a single-solvent system using N,N-dimethylformamide with nano-sized spherical alumina particles was formulated, Marangoni flow (circulation flow) was created in the ink droplets by combining N,N-dimethylformamide and fotmamide with the spherical alumina powders as a co-solvent ink system. We have investigated the effect of these two different flows on the formation of ceramic films by inkjet printing method, The packing density of the ceramic films printed with two different ink systems (single- and co-solvent systems) and their surface roughness were characterized. The dielectric properties of these inkjet-printed ceramic films such as dielectric constant and dissipation factor were also studied in order to evaluate the feasibility of their application to the electronic ceramic package substrate.

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NUMERICAL SIMULATION OF LASER WELD POOL GEOMETRY USING ENTHALPY METHOD (엔탈피 모델을 이용한 레이저 용융풀 형상에 대한 수치해석연구)

  • Lee, T.;Cheung, H.;Shin, S.
    • Journal of computational fluids engineering
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    • v.18 no.4
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    • pp.61-68
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    • 2013
  • Laser welding is widely used in the industry for the advantage of small heat affected zone and short weld process time. Conduction limit welding can be used to modify the surface characteristic and it is important to identify the heat affecting area correctly for the improvement of manufacturing accuracy. Since time and length scale associated with laser welding process are extremely small, numerical study can be a useful tool. In this study, two-dimensional axi-symmetric version of energy equation with enthalpy method has been used to analyze the effect of laser input conditions on final shape by the laser welding process. The proposed numerical procedure has been benchmarked with several experimental results and compared well. The modified Marangoni and Peclet number have been introduced using controllable input variables. Simple parametric researches have been performed for high Pr number material. The results show that higher Marangoni number increase fluid mixing, thus generating convex type weld pool. On the other hand, the width of the weld pool is proportional to Peclet number.

A Droplet-Manipulation Method using Opto-thermal Flows on Amorphous Silicon Thin Film (비결정질 실리콘 박막 상에서의 광열 유동을 이용한 액적 조작)

  • Lee, Horim;Yoon, Jin Sung;Kim, Dong Sung;Lim, Geunbae
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.1
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    • pp.91-96
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    • 2014
  • We present a droplet-manipulation method using opto-thermal flows in oils. The flows are originated from Marangoni and buoyancy effects due to temperature gradient, generated by the adsorption of light on an amorphous silicon thin film. Using this method, we can transport, merge and mix droplets in an extremely simple system. Since the temperature rise during the operation is small, this method can be used for biological applications without the damage on cell viability.

Influence of Surfactant on Mass Transfer of Vertical Absorber (수직관 흡수기의 물질전달에 미치는 계면활성제의 영향)

  • Kwon, Oh-Kyung;Yoon, Jung-In;Yun, Jae-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.5
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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$_{f}$ $^{n}$ .

Enhancement of Heat and Mass Transfer by Insert Spring in a Vertical Absorber with Surfactant

  • Yoon, Jung-In;Choi, Kwang-Hwan;Moon, Choon-Geun;Sarker M.M.A;Kwon, Oh-Kyung
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.8
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    • pp.1239-1250
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    • 2004
  • This research was concerned with the enhancement of heat transfer by surfactant added to the aqueous solution of LiBr. Different vertical tubes were tested with and without an additive of normal octyl alcohol. The test tubes are a bare inner surface. a groove inner surface, a corrugated inner surface and a spring inserted inner surface tubes. The additive concentration was about 0.08 mass%. The heat transfer coefficient was measured as a function of the film Reynolds number in the range of 20~200. Experiments were carried out at higher cooling water temperature of $35^{\circ}C$ to simulate an air cooling condition for several kinds of absorber testing tubes. The experimental results were compared with and without surfactant. The enhancement of heat transfer by Marangoni convection effect which was generated by addition of the surfactant is observed in each test tube. Especially, it is clarified that the tube with an inserted spring has the highest enhancement effect.