• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.373-380
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• 2014

Film flows applied to shell-and-tube heat exchangers in various industrial fields have been studied for a long time. One boundary of the film flow interfaces with a fixed wall, and the other boundary interfaces with a gaseous region. Thus, the flows become so unstable that wavy behaviors are generated on free surfaces as the film Reynolds number increases. First, high-amplitude solitary waves are detected in a low Reynolds number laminar region; then, the waves transit to a low-amplitude, high frequency ripple in a turbulent region. Film thickness is the most significant factor governing heat transfer. Since the wave accompanied in the film flow results in temporal and spatial variations in film thickness, it can be of importance for numerically predicting the film's wavy behavior. In this study, various turbulent models are applied for predicting low-amplitude ripple flows in turbulent regions. The results are compared with existing experimental results, and finally, the applied turbulent models are appraised in from the viewpoint of wavy behaviors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1169-1176
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• 2011

Liquid film flows are classified into waveless laminar, wavy laminar, and turbulent flows depending on the Reynolds number or the flow stability. Since the wavy motions of the film flows are so intricate and nonlinear, studies on them have largely been experimental. Most numerical approaches have been limited to the waveless flow regime. The various free surface-tracking schemes adopted for this problem were used to more accurately estimate the average film thickness, rather than to capture the unsteady wavy motion. In this study, the wavy motions in laminar wavy liquid film flows with Reynolds numbers of 200-1000 were simulated with various numerical schemes based on the volume of fluid (VOF) method for interface tracking. The results from each numerical scheme were compared with the experimental results in terms of the average film thickness, the wave velocity, and the wave amplitude.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.2
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• pp.15-22
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• 1988

실제의 흡기관에서는 단면이 일정한 직관이 아니며, 피스톤기관의 흡기관은 단면변화가 불가피하여 액적은 소성으로 인한 관벽과의 충돌로 부착하게 되고 액적부유율은 더욱 작게 된다는 D.A. Trayser, W.E. Ranz등의 보고가 있다. 또 보제행남들은 액막류의 발생이 유해배기 가스를 증가시키고 액막류의 감소는 기통사이의 연료분배의 불균일도를 저하시키므로 NOx, HC, CO가 크게 감소된다고 보고하였다. 이와같이 액막유의 존재는 각 실린더에 유입하는 연료의 질적차이를 가져오기 때문에 액막유를 분리제거하는 방법의 연구도 많이 이루어지고 있으나 아직 실용상에 문제가 많은 것으로 남아있다. 따라서 본 고에서는 이와같이 문제되고 있는 흡기관내 액막유동의 거동을 고찰하기 위하여 액막두께 변동을 측정하는 방법에 대하여 저자들이 사용하였던 방법과 그외 초음파를 이용한 액막두께 측정법을 소개하고자 한다.

• Membrane Journal
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• v.8 no.3
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• pp.138-147
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• 1998

This paper compared selectivities and mass transfer rates of valuable aromatics (naphthalene group: carbon number 10-12) in the light cycle oil obtained from solvent extraction (SE) with those obtained from liquid membrane permeation (LMP). An aqueous solution of dimethylsulfoxide (DMSO) and an aqueous solution of saporrin and DMSO were used as extraction solvent of SE and the membrane phase of LMP, respectivdy. Selectivities of naphthalene group in reference to n-nonane obtained from SE runs were rapidly increased with decreasing the operating temperature, whereas, those obtained from LMP runs were remained constant throughout the operating temperature. At room temperature, selectivities of naphthalene group obtained from SE were greater than those from SE. Furthermore, mass transfer rates of naphthalene group by SE and LMP were measured in a baffled batch stirred vessel. It was found that the extraction rates of SE were faster by about 280 times than the permeation rates of LMP.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.208-213
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• 2001

The minimum heat flux conditions are experimentally investigated for the subcooled liquid film flow on the horizontal plate. The experimental results show that the minimum heat flux point temperature becomes higher with the increase of the velocity and the subcooling of the liquid film flow. However, the effect of distance from the leading edge of the heat transfer plate on the minimum heat flux is almost negligible. Also, the experimental results show that the propagation velocity of wetting front increase with increasing the velocity and the subcooling of the liquid film flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.960-965
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• 2001

The minimum heat flux conditions are experimentally investigated for the subcooled liquid film flow on the horizontal plate. The experimental results show that the minimum heat flux point temperature becomes higher with the increase of the velocity and the subcooling of the liquid film flow. However, the effect of distance from the leading edge of the heat transfer plate on the minimum heat flux is almost negligible. Also, the experimental results show that the propagation velocity of wetting front increases with increasing the velocity and the subcooling of the liquid film flow.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.131-135
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• 2001

The atomization characteristics of an annular liquid (water) sheet of small radius with a core gas (air) flow were studied. Different sizes of annular gaps (0.2, 0.4 and 0.8 mm) were tested to find the effect of liquid sheet thickness on SMD. The inner diameter of the gas port for the core gas flow was 4 mm. Cross-section averaged SMD was measured for various liquid and gas velocities. Regions of the SMD decrease with the increase of the liquid velocity always existed regardless of the liquid sheet thickness. This attributes to the transition of the flow patterns of spray and also to the aerodynamic interaction between the atomizing gas and the ripples on the liquid sheet surface.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.6
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• pp.81-90
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• 1992

This paper deals with an experimental study on the initial condition of liquid film surface waves disintegration and investigation on the behavior of liquid film surface waves formed by the high speed air flow on the solid plane surface. The authors conducted the qualitative and quantitative study to in vestigate the liquid film flow phenomena, the liquid film disintegration mechanism, and droplet formation process with breaking the liquid film surface wave. The newly devised transparent rectangular test section which has semi-two-dimensional flow at the center of the bottom was introduced to perform the experimental study, and it can generate the uniform thickness liquid film at the bottom. The strobo streak camera was used to obtain the instantaneously transformed photographs. The electronic measuring device was also used to measure the liquid film thickness variation in order to perform the easy and effective analysis of complex flow phenomena in the air-water cocurrent flow.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.201-207
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• 2001

We modeled the liquid film dryout(LFD) process for both tube and annulus which have uniformly heated vertical channels. We set phenomenological initial conditions in the model. The initial void fraction on the onset of the annular flow location is derived from the physical chum-to-annular flow criterion with the help of the drift-flux-model. The initial thermodynamic-equilibrium-quality is calculated by iteration with the flow quality to find the onset of the annular-flow location. Present model tends to predict very well at the lower exit quality but under-estimates at the higher exit quality. We found that the prediction error of the present model is gradually bigger as the inlet subcooling approaches near the saturation. We obtained excellent results for both tube and annulus channels as the mean of 0.97 and root-mean-square error of 11% for the number of 3883 experimental data on tubes, and of 0.96 and of 12% for 593 on annuli. The present model extended the applicable range to the relatively low exit quality region than previous LFD models.

• Journal of Korean Society for Quality Management
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• v.9 no.2
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• pp.15-25
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• 1981

This paper deals with the experimental study on the behavior of fuel flow in intake manifold of gasoline engine. The main purpose of this study is an analysis of air stream velocity, behavior of liquid film flow, generation of atomization and atomization rate by using the basic apparatus which is manufactured the visible, straight tube type model of intake manifold. As the result, we have found factors which influenced on the behavior of liquid film flow in intake manifold.