• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.2036-2045
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• 1996

An experimental study has been performed to obtain the effect of relative velocity between droplet and environmental gas on the evaporation of a n-heptane free droplet of 180 $\mu$m in diameter flying in a hot and normal pressure air flow. Measurement of droplet diameter and velocity was conducted in a series of time by an electrically controlled optical system. From the experimental results, an empirical equation associated with the relation between evaporation rate constant and relative velocity was obtained.

• Journal of ILASS-Korea
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• v.17 no.1
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• pp.9-13
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• 2012

This study investigates experimentally evaporation characteristics of nanofluid droplets containing 50 nm alumina($Al_2O_3$) particles and the wettability changes on a hydrophilic glass surfaces. From the captured digital images by using a CMOS camera and a magnifying lens, we examined the effect of particle concentration on droplet evaporation rate which can be indirectly deduced from the measured droplet volumes varying with time. In particular, with the use of a digital image analysis technique, the present study measured droplet perimeters and the contact angles to study the wetting dynamics during evaporating process. In addition, we compared the measured total evaporation time with theoretically estimated values. It was found that as the volume fractions of nanofluid increased, the total evaporation time and the initial contact angles decreased, while the droplet perimeters increased.

• Journal of ILASS-Korea
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• v.26 no.2
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• pp.73-80
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• 2021

Evaporation characteristics of single butanol gel fuel were investigated in different mass ratios of gellant and ambient temperatures. Gel fuel was made by adding the pure water and hydroxypropylmethyl cellulose (HPMC) into the 1-butanol. Increase of viscosity was observed when the loading of HPMC increased. The evaporation process of gel droplet could be divided into three stages: droplet heating, micro-explosion and crust formation. Elevation of ambient temperature helped boost the evaporation in all experimental cases, but the effect was mitigated when the mass ratio of HPMC increased. Increase of HPMC weight ratio reduced the evaporation rate.

• Journal of Energy Engineering
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• v.11 no.1
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• pp.74-80
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• 2002

In this study, a numerical method for fuel droplet evaporation in cylinder of S.I. engine is presented. This study was newly defined non-dimensional critical droplet lifetime and modeled heating and evaporation processes of fuel droplet during intake and compression stroke of gasoline engine. The simulation results show that simultaneous increase of gas temperature and pressure in compression stroke seems to have compensative effect on droplet gasification rate. The environment variations in cylinder have little effect on the fuel droplet gasification process. The droplet size for full evaporation at the end of compression stroke can be estimated using this program.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.11
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• pp.873-877
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• 2012

The effect of oxygen pressure in the synthesis of ZnO nanostructures through thermal evaporation of Zn powder was investigated. The thermal evaporation process was carried out in oxygen ambient for 1 hr at $1,000^{\circ}C$ under different pressures. The oxygen pressure was changed in range of 0.5 ~ 900 Torr. Any nanostructure was not formed on the specimens prepared at oxygen pressures lower than 10 Torr. When oxygen pressure was 100 Torr, ZnO nanowires were observed. With increasing the oxygen pressure to 500 Torr, the morphology of ZnO nanostructures changed from wire to tetrapod. For all the samples, room temperature photoluminescence spectra show a strong green emission peak at around 550 nm.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.424-427
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• 2018

The effect of oxygen pressure in the synthesis of $SnO_2$ micro/nanocrystals through thermal evaporation of Sn powder was investigated. The thermal evaporation process was performed at $1000^{\circ}C$ for 1 hr under various oxygen pressures. The pressure of oxygen changed from 10 to 500 Torr. The morphology of $SnO_2$ crystals changed drastically with oxygen pressure. $SnO_2$ nanoparticles with an average diameter of 120 nm were formed at oxygen pressure lower than 10 Torr. $SnO_2$ nanowires were grown under an oxygen pressure of 100 Torr. The nanowires have diameters in the range of 100 ~ 500 nm and lengths of several tens of micrometers. As increasing the oxygen pressure to 500 Torr, the sizes of wires increased. A strong visible emission peak centered at about 500 ~ 600 nm was observed in the room temperature cathodoluminescence spectra of all the products.

• Asian-Australasian Journal of Animal Sciences
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• v.2 no.3
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• pp.271-272
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• 1989

• Journal of the Korean Society of Combustion
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• v.13 no.3
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• pp.17-23
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• 2008

The spray combustion and spray cooling depends on droplet evaporation. So, evaporation model for spray has been requested and lots of investigation has been done and various reliable models have been developed also for last few decades. In the present study, One dimensional quasi-steady spherically symmetric droplet evaporation model for micro-gravity is developed. The gas phase was assumed as steady state and the thermophysical properties are calculated as a function of temperature, pressure and composition and the properties used in the model was validated by NIST web data and overall evaporation history results was compared with experimental results by Nomura and Qasim and gave satisfactory agreements. Through this model, diverse phenomenon was investigated, especially regarding the effects of ambient pressure and temperature. The effects of pressure for the droplet evaporation time were studied. The high pressure increased the droplet surface temperature and made effect on the evaporation time depend on atmospheric temperature. The role of the ambient temperature was investigated and explained. The basic investigation for the evaporation process according to variation of droplet diameter and surface temperature were also investigated and the well-known phenomena, like D-square-law, were reported, too.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.6
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• pp.375-382
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• 2005

This paper presents the results of experimental investigation for the effect of heat conduction on the evaporation cooling of water droplet in the process of heat treatment. The experiments are mainly focused on the surface temperature, the surface roughness and the droplet diameter at aluminum. The range of surface temperature is from $80^{\circ}C$ to $140^{\circ}C$, surface roughness is from $R_a=0.18{\mu}m$ to $R_a=1.36{\mu}m$ and droplet diameter is from 2.4 mm to 3.0 mm. The results show that the total evaporation time is shorter for the larger surface roughness, the time averaged heat flux has maximum value for the larger surface roughness and exist the critical heat flux. The total evaporation time has a big influence on the evaporation region for the smaller droplet size, but the total evaporation time has not influence on the nuclear boiling region.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.1-8
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• 2021

Droplet evaporation has been known as a common phenomenon in daily life, and it has been widely used for many applications. In particular, the influence of the different heated substrates on evaporation flux and flow characteristics is essential in understanding heat and mass transfer of evaporating droplets. This study aims to simulate the droplet evaporation process by considering variation of thermal property depending on the substrates and the surface temperature. The commercial program of ANSYS Fluent (V.17.2) is used for simulating the conjugated heat transfer in the solid-liquid-vapor domains. Moreover, we adopt the diffusion-limited model to predict the evaporation flux on the different heated substrates. It is found that the evaporation rate significantly changes with the increase in substrate temperature. The evaporation rate substantially varies with different substrates because of variation of thermal property. Also, the droplet evaporates more rapidly as the surface temperature increases owing to an increase in saturation vapor pressure as well as the free convection effect caused by the density gradient.