• 한국자동차공학회논문집
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• 제12권1호
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• pp.25-31
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• 2004

Two-dimensional laser visualization methods have been used in the study of breakup and atomization processes of non-evaporating diesel sprays. A single-hole spray injected into a quiescent atmospheric environment was visualized by the LIF(Laser Induced Fluorescence) and scattering technique. The LIF technique could be implemented to take the images which are magnified enough to show the shape of liquid ligaments and small droplets. The spontaneous scattering and fluorescent images of sprays were also taken to investigate the atomization of droplets. In the tip and periphery of a spray. the scattering light is bright and the ratio of fluorescent/scattering intensity is lower. This characteristics indicate the very high number density of small droplets which are well atomized.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2001년도 제16회 학술발표회 논문초록집
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• pp.21-22
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• 2001

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 하계학술발표대회
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• pp.117-117
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• 2005

• 대한기계학회논문집B
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• 제20권2호
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• pp.632-640
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• 1996

석탄슬러리 액적은 석유와 취급의 유사성 때문에 석유 대체에너지로서 중용하게 인식되어지고 있으며, 석유계의 연료와 비슥한 방법으로 분무연소 시키는 것이 가능하여 종래의 중유사용 연소장치를 최소한 개조하여 사용할 수 있다는 이점이 있다. 따라서 석탄슬러리 액적의 연소에 관한 연구가 활발히 진행되고 있으나 혼합되는 연료의 종류 또는 연소 및 열전달기수에 대한 해석 방법이 다양하여 아직 체계화되지 못하고 있으며 논란의 여지도 없다.

• 대한기계학회논문집B
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• 제30권7호
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• pp.663-670
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• 2006

The presented study aims to investigate the colloidal droplet deposition caused by evaporation of the liquid. In the numerical analysis, the evaporation is carried out by using different evaporation function intended to obtain different shape of solute deposition. In the experiment, the colloidal droplets of different solvents are placed on a glass plate and the surface profiles are measured after drying the solvents of the droplets to investigate the effect of the solvent evaporation on the final deposition profile. Comparing the surface profiles obtained under different conditions, the optimum drying conditions of colloidal droplets are, determined to obtain uniform surface profiles. The numerical results showed that ring-shaped deposition of solute was formed at the edge of the droplet due to the coffee stain effect and the height of the ring was reduced at the lower evaporation rate. The experiments showed that the boiling point of a solvent was critical to the surface uniformity of the deposition profile and the mixture of solvents with different boiling points influenced the uniformity as well.

• 설비공학논문집
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• 제16권5호
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• pp.467-474
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• 2004

This paper presents the results of an experimental investigation for the effect of radiant heat on the evaporation cooling of water droplet in the process of fire extinguishing. The experiments are mainly focused on the surface temperature, the surface roughness and the droplet diameter. The range of surface temperature is T$_{s}$ =80－14$0^{\circ}C$, surface roughness is R$_{a}$=0.08－0.64 ${\mu}{\textrm}{m}$ and the droplet diameter is $\Phi$=3.0 mm in the radiation. The results show that the evaporation time is shorter for the larger surface roughness and the volume of droplet increased when the surface roughness is 0.64 ${\mu}{\textrm}{m}$ at the surface temperature 127$^{\circ}C$. When the surface roughness is 0.64 ${\mu}{\textrm}{m}$, the heat flux is larger than the surface roughness is 0.08 ${\mu}{\textrm}{m}$ at the surface temperature 81$^{\circ}C$.>.>.

• 한국군사과학기술학회지
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• 제3권1호
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• pp.207-217
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• 2000

A fire fighting characteristic by a single evaporating droplet in the case of a fire of military enclosure space was studied experimentally. Transient cooling of solid surface by water droplet evaporation has been investigated through controlled experiments using a heated brass cylinder. Quantitative predictions of droplet evaporation time and in-depth transient temperature distribution in solid have been made. The particular interest was in the removal of thermal energy from the heated cylinder by evaporative cooling. A $10{\mu}1$ single droplet is deposited on a horizontal brass surface with initial temperatures in the range of $90^{\circ}C{\sim}130^{\circ}C.$ The results can be summarized as follows; Evaporating droplet was divided into three different configuration. Evaporation time was predicted as a function of initial surface temperature ($t_c=492.62-6.89T_{s0}+0.0248T_{s0}^2).$ The contact temperature was predicted as a function of initial surface temperature( $T_{i}$=0.94 $T_{s0}$+1.4), The parameter ${\beta}_o$ was predicted as a function of initial surface temperature( ${\beta}_0$ : 0.O0312 $T_{s0}+0.932$)>)>)

• 대한기계학회논문집B
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• 제20권5호
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• pp.1700-1716
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• 1996

The two-dimensional, unsteady, laminar conservation equations for mass, momentum, energy and species transport in the gas phase and mass, momentum and energy in the liquid phase are solved simultaneously in spherical coordinates in order to study heating and vaporization of a droplet entrained in the oscillating flow. The numerical solution gives the velocity and temperature distribution in both gas and liquid phase as a function of time. When the gas flow oscillates around an vaporizing droplet, the liquid flow circulates in the clockwise or counterclockwise direction and the temperature distribution in the liquid phase changes its shapes, depending on the gas fow direction. When the gas flow changes its direction of circulating liquid flow is opposite to the gas flow, forming two vortex circulating in the opposite direction. During the heating period, the difference in the maximum and minimum temperature is large, followed by the almost uniform temperature slightly below the boiling temperature. The mass and heat transfer from the droplet depend on the droplet temperature, droplet diameter and the magnitude of relative velocity, giving the droplet lifetime different from the d$^{2}$-law.

• 대한기계학회논문집B
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• 제31권6호
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• pp.558-565
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• 2007

Many studies of microdroplet evaporation from solid surfaces were made with priority given to inkjet printing and dye painting techniques. The objective of these studies is how to evaporate a droplet quickly and uniformly. Also it is necessary to prevent evaporation of a droplet to observe cells in a droplet generated through cell-patterning. In general, an identical volume of a water droplet on hydrophobic surfaces evaporates slower than that on hydrophilic surfaces. In this study, we observe the evaporation process of a droplet on various hydrophobic surfaces and calculated the evaporation rate considering the droplet geometry such as contact angle and height. This study also proposes a new model based on the fact that evaporation mode at the edge of a droplet is different from that at the outer surface of a droplet as the contact angle changes during evaporation. Finally, we reveal the cause fur the increase of evaporation flux and show that the ratio of edge evaporation to total evaporation increases with time.

• 한국분무공학회지
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• 제5권1호
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• pp.13-22
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• 2000

The present study has numerically analyzed the vaporization characteristics of fuel droplets in the high temperature convective flow field. The axisymmetric governing equations for mass, momentum, energy, and species are solved by an iterative and implicite unstructured finite-volume method. The moving boundary due to vaporization is handled by the deformable unstructured grid technique. The pressure-velocity coupling in the density-variable flows is treated by the SIMPLEC algorithm. In terms of the matrix solver, Bi-CGSTAB is employed for the numerically efficient and stable convergence. The n-decane is used as a liquid fuel and the initial droplet temperature is 300K. Computations are performed for the nonevaporating and evaporating droplets with the relative interphase velocity(25m/s). The unsteady vaporization process has been simulated up to the nondimensional time, 25. Numerical results indicate that the mathematical model developed in this study succesfully simulates the main features of the droplet vaporization process in the convective environment.