• Journal of the Korean Society of Safety
• /
• v.19 no.3 s.67
• /
• pp.14-19
• /
• 2004

The objective of the present work is to examine evaporation cooling of droplet due to surface roughness under radiative heat input condition. The surface temperatures varied from $80\~160^{\circ}C$ on aluminum alloy (AL 2024) and surface roughness was $0.18{\mu}m,\;1.36{\mu}m$. The results are as follows; Regardless of surface roughness under radiative heat input condition, as droplet diameter is larger, the in-depth temperature of solid decreases and evaporation time increases. In the case of $0.18{\mu}m\;and\;1.36{\mu}m$ of surface roughness, the larger the surface roughness is, the less the evaporation time is and the larger the temperature within the solid is. In the case of $Ra=0.18{\mu}m$ evaporation time and time averaged heat flux for radiative heat input case is shorter than for the conductive case.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.05a
• /
• pp.289-290
• /
• 2012

In this study, it was evaluated about shrinkage properties of high strength concrete according to poly mix fiber and moisture evaporation condition. As a results, When concrete was mixed with poly mix fiber of spalling control, it reduced effect of shrinkage independent of the evaporation conditions of unsealed and sealed.

• Journal of the Korean Society for Heat Treatment
• /
• v.19 no.3
• /
• pp.141-148
• /
• 2006

An experimental study is presented for water droplet impingement on a steel surface in the process of heat treatment. The objective of the present work is to examine characteristic of evaporation cooling due to surface roughness and droplet diameter under conductive heat input condition. The surface temperatures varied from $80{\sim}155^{\circ}C$, surface roughness was from $R_a=0.12{\mu}m$ to $R_a=1.14{\mu}m$ and droplet diameter was from 2.4 mm to 3.0 mm. The results show that the total evaporation time is shorter for the larger surface roughness and the smaller droplet size, the time average heat flux has maximum value for the larger surface roughness and the smaller droplet size. The total evaporation time has not influence on the nuclear boiling region.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.6
• /
• pp.2125-2131
• /
• 1991

Evaporation rate constant, obtained by in this experimental study, of freely falling liquid fuel droplet on the condition of hot and pressurized environment are converted to critical evaporation constant according to Eq. of Ranz and Marshall. Critical evaporation constant, on constant environment pressuire, actively increase almost linearly with environment temperature increasing, but, on constant temperature, increases more or less with pressure increasing. Multycomponent droplet mixed with the fine fuel having a different of boiling point evaporate in order to boiling point, and each evaporation rate constant of mixed fuel equal to each fuel.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.1
• /
• pp.79-89
• /
• 2019

The field measurement and laboratory experiment were conducted to investigate the effect of reducing the surface temperature of the functional aspect of the heat island phenomenon of the permeable block which is made the recycled synthetic resin rather than the existing concrete permeable block. Field measurement was taken for 3 days in consideration of dry condition and wet condition and laboratory experiment was divided into dry condition, rainfall simulating condition, and wetting condition. The variations of temperature and the evaporation rate of water moisture content after experiment were confirmed. As a result of field measurement, it is confirmed that the surface temperature decreases due to the difference in albedo of the pore block surface rather than the cooling effect due to the latent heat of vaporization. The evaporation of moisture in a dry state where drought persisted or a certain level of moisture was not maintained in the surface layer. As a result of laboratory experiment, resin permeable block gives higher surface temperature when it is dry condition than concrete permeable block, but the evaporation of water in the pore is kept constant by capillary force in rainfall simulation condition, and higher temperature reduction rate. As a result of measuring the evaporation rate after laboratory experiment, it is confirmed that the effect of reducing temperature is increased as the evaporation rate of water is higher. Based on these results, correlation formula for evaporation rate and temperature reduction rate is derived.

• Journal of ILASS-Korea
• /
• v.26 no.2
• /
• pp.73-80
• /
• 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 the Korean earth science society
• /
• v.24 no.1
• /
• pp.22-29
• /
• 2003

Temporal and spatial variability of precipitation (P), evaporation (E), and moisture balance (P-E; precipitation minus evaporation) has been investigated over the tropical ocean during the period from January 1998 to July 2001. Our data were analyzed by the EOF method using the satellite P and E observations made by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and the Special Sensor Microwave/Imager (SSM/I). This analysis has been performed for two three-year periods as follow; The first period which includes the El Ni${\tilde{n}}$o in early 1998 ranges from January 1998 to December 2000, and the second period which includes the La Ni${\tilde{n}}$o events in the early 1999 and 2000 (without El Ni${\tilde{n}}$o) ranges from August 1998 to July 2001. The areas of maxima and high variability in the precipitation and in the P-E were displaced from the tropical western Pacific and the ITCZ during the La Ni${\tilde{n}}$o to the tropical middle Pacific during the El Ni${\tilde{n}}$o, consistent with those in previous P studies. Their variations near the Korean Peninsula seem to exhibit a weakly positive correlation with that in the tropical Pacific during the El Ni${\tilde{n}}$o. The evaporation, out of phase with the precipitation, was reduced in the tropical western Pacific due to humid condition in boreal summer, but intensified in the Kuroshio and Gulf currents due to windy condition in winter. The P-E variability was determined mainly by the precipitation of which the variability was more localized but higher by 2-3 times than that of evaporation. Except for the ITCZ (0-10$^{\circ}$N), evaporation was found to dominate precipitation by ${\sim}$2 mm/day over the tropical Pacific. Annual and seasonal variations of P, E, and P-E were discussed.

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

• Transactions on Electrical and Electronic Materials
• /
• v.7 no.1
• /
• pp.21-25
• /
• 2006

In this study, liquid crystal (LC) aligning properties for homeotropic alignment on the $SiO_x$ thin film by electron beam evaporation method with electron beam system in accordance with the evaporation angles were investigated. Also, the control of pretilt angles homeotropic aligned LC on $SiO_x$ thin film as the function of the evaporation angles were studied. The uniform vertical LC alignment on the $SiO_x$ thin film surfaces with electron beam evaporation was achieved with all of the thin film angle conditions. It is considerated that the LC alignment on the $SiO_x$ thin film by electron beam evaporation is attributed to elastic interaction between LC molecules and micro-grooves at the $SiO_x$ thin film surface created by evaporation. The values of the pretilt angles according to the evaporation angle were from about $0.7^{\circ}$ to about $3.4^{\circ}$. The highest pretilt angles of about $3.4^{\circ}$ in aligned NLC on the $SiO_x$ thin film surfaces by electron beam evaporation were measured under the condition of $45^{\circ}$. Also, good LC alignment states on the treated $SiO_x$ thin film layer by electron beam evaporation were observed at annealing temperature of $250^{\circ}C$. Consequently, the high pretilt angle and the good thermal stability of LC alignment on the $SiO_x$ thin film by electron beam evaporation can be achieved.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.5
• /
• pp.37-48
• /
• 2016

This study aims to figure out the behavior of runoff and drainage of pervious sidewalk block in actual construction environment by experiments. The specimens with surface layer and bedding layer are subjected to the drainage test by considering unsaturated condition and unique rainfall condition in urban areas. The repeated drainage test and clogging test were conducted with time intervals, and 3D X-ray CT image analysis and evaporation test were carried out for a quantitative analysis of drainage test. The results present that the spatial distribution of pores by evaporation for time intervals induces runoff. Especially, the bedding layer under the block is significantly critical in overall hydraulic behavior such as drainage and evaporation compared to the surface layer. Moreover, the sediments in pores promote the change in pores by evaporation and this induces deteriorated drainage capacity which is hard to recover. In addition, it is revealed that the maximum runoff height grows as the drainage capacity declines depending on the pre-wetting condition.