• Title/Summary/Keyword: evaporation characteristics

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Evaporation characteristics of materials from resistive heating sources(I) (저항가열원에 의한 물질의 증발특성(I))

  • 정재인;임병문;문종호;홍재화;강정수;이영백
    • Journal of the Korean institute of surface engineering
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    • v.24 no.1
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    • pp.25-30
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    • 1991
  • The evaporation characteristics of Ag, Al, Au, Cr. Cu, In, Mg, Mn, Pb, Pd, Si, SiO, Sn, Ti and Zn with the various resistive heating sources have been studied. The employed sources are refractory metal (Mo, Ta and W) boats, W-wire, ceramic (usually Al2O3)-coated and -barriered refractory metal boats, and special boats such as baffled boats and intermetallic boats (nitride compound and graphite). We investigated the melting mode, evaporation rate at a specific power, and lifetime of the sources. A special boat holder is also discussed which is needed to cool the sources at a large heat capacity.

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Characteristics of Evaporative Heat Transfer and Pressure Drop of Carbon Dioxide and Correlation Development near the Critical Point (임계점 부근에서 이산화탄소의 증발열전달 및 압력강하 특성 연구와 상관식 개발)

  • 윤석호;조은석;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.6
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    • pp.530-537
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    • 2004
  • In recent years, carbon dioxide among natural refrigerants has gained consider-able attention as an alternative refrigerant due to its excellent thermophysical properties. However, few investigations have been performed to develop useful correlations of heat trans-fer coefficients and pressure drop during evaporation of carbon dioxide. This study is aiming at providing the characteristics of heat transfer and pressure drop during the evaporation process of carbon dioxide. Heat is provided by a direct heating method to the test section, which was made of a seamless stainless steel tube with an inner diameter of 7.53 mm, and a length of 5.0 m. Experiments were conducted at saturation temperatures of -4 to 2$0^{\circ}C$, heat fluxes of 12 to 20 ㎾/$m^2$ and mass fluxes of 200 to 530 kg/$m^2$s. A comparison of different heat transfer correlations applicable to evaporation of carbon dioxide has been made. Based on the experiments for evaporation heat transfer and pressure drop, new correlations were developed. The newly developed empirical correlations for the heat transfer and pressure drop show average absolute deviations of 15.3% and 16.2%, respectively.

Experimental Study on R-134a Evaporation Heat Transfer Characteristics in Plate and Shell Heat Exchanger (판각형 열교환기내의 R-134a 증발열전달 특성에 관한 실험적 연구)

  • Kim, Su-Jin;Park, Jae-Hong;Seo, Moo-Gyo;Kim, Young-Soo
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.248-253
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    • 2001
  • An experiment was carried out to investigate the characteristics of the evaporation heat transfer for refrigerant R-134a flowing in a plate and shell heat exchanger. The data are useful in designing more compact and effective evaporators for various refrigeration and air conditioning systems. Two vertical counterflow channels were formed in the exchanger. The R-134a flows up in one channel exchanging heat with the hot water flowing down in the other channel. The effects of the average heat flux, mass flux, saturation temperature and vapor quality were examined in detail. The present data show that the evaporation heat transfer coefficient increases with the vapor quality. A rise in the refrigerant mass flux causes an increase in the $h_r$ value. A rise in the average imposed heat flux causes an increase in the $h_r$, value at the low quality. Finally, at a higer refrigerant saturation temperature the $h_r$, value is found to be lower.

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Optimization of MgO Evaporation for PDP Efficiency and Discharging Characterization (프라즈마 디스플레이 패널의 고효율화를 위한 MgO 증착 조건의 최적화 및 PDP 방전특성 분석)

  • Kwon, Sang-Jik;Kim, Yong-Jae;Li, Zhao-Hui;Kim, Kwang-Ho;Yang, Soon-Seuk
    • Proceedings of the IEEK Conference
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    • 2006.06a
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    • pp.569-570
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    • 2006
  • Effects of the evaporation rate of MgO films using electron beam were investigated on the MgO properties and the discharge characteristics of the plasma display panel (PDP). The evaporation rate was changed from $3{\AA}$/sec to $15{\AA}$/sec at a substrate temperature of $300^{\circ}C$. MgO properties such as crystal orientation, surface roughness, contact angle, and film structure were inspected using XPS, AFM, drop shape analysis and SEM. We also studied the relation between MgO properties and PDP discharging characteristics. The minimum firing voltage and maximum efficacy were obtained at evaporation rate of $5{\AA}$/sec. In the MgO film deposited at $5{\AA}$/sec, (200) orientation was most intensive and surface roughness was minimum.

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Estimation of small pan evaporation using temperature data (기온자료를 이용한 소형증발접시 증발량 산정)

  • Rim, Chang-Soo
    • Journal of Korea Water Resources Association
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    • v.50 no.1
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    • pp.37-53
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    • 2017
  • Pan evaporation has been used as an indirect method for the estimation of reservoir evaporation. Therefore, in this study, pan evaporation estimation equations using only temperature data were suggested in the case that available meteorological data is limited. A formula for estimating the pan evaporation were suggested by comparing estimated pan evaporation with measured pan evaporation in 12 study areas in Korea. The suggested pan evaporation equations were verified in 44 study areas by comparing not only with temperature-based equations but also with equations using other meteorological data (temperature, wind speed, relative humidity, and sunshine duration). The study results indicate that the suggested equations in this study provide much better pan evaporation estimates, compared with other temperature-based equations. Overall, the suggested equations provide appropriate pan evaporation estimates in most of 56 study areas. Therefore, the suggested equations using only temperature data in this study are considered appropriate for the estimation of pan evaporation in Korea especially in the case that available meteorological data is limited. In the future, using the air temperature and pan evaporation data measured at the reservoir, further research is needed to examine the applicability of suggested equations for the estimation of reservoir evaporation.

An Experimental Study on the Evaporation and Ignition of CWS Droplets (CWS액적의 증발 및 점화에 관한 실험적 연구)

  • 안국영;백승욱;김관태
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.5
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    • pp.1246-1252
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    • 1993
  • Coal-Water slurry (CWS) is a new potential form of fuel for use in power plants and industrial furnaces. The evaporation and ignition characteristics of CWS have been studied in the post-flame region generated by a flat flame burner. Individual droplets with initial diameters of 1-3mm were supported around the thermocouples and raidly exposed to a hot gas stream. The gas temperature ranged between $950^{\circ}C$ and 1600.deg. C at atmospheric pressure. The effect of droplet size, gas temperature and radiative heat transfer by screen were studied experimentally. The ignition criterion was either a rapid temperature rise in time-temperatuire curves or onset of visible flame in experiment. Incresing the gas temperature or decreasing the droplet size reduced the time required for evaporation and ignition.

The characteristics of heat transfer coefficient for falling-film evaporation on a horizontal tube with aqueous LiBr solution (LiBr 수용액의 수평관 유하액막 증발에 있어서의 열전달계수 특성)

  • Ji, Yong-Hae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.2
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    • pp.294-302
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    • 1997
  • Falling-film evaporation experiments for aqueous solution of lithium bromide (LiBr) were performed on a horizontal smooth 19.05-mm-dia copper tube. Average heat transfer coefficients were obtained with varied film Reynolds numbers, system pressures, LiBr concentrations and degrees of wall superheat. Heat transfer coefficients increase with increasing system pressure and decreasing concentration. For degrees of wall superheat, the heat transfer coefficient did not't show the distinct trend. For this experimental ranges, heat transfer coefficients showed maximum values at an optimal film Reynolds number. The results of this work were compared with pool boiling data reported previously, and it was shown that the heat transfer performance is superior to the pool boiling.

Characteristics of ZnO Nanowire Fabricated by Thermal Evaporation Method Depending on Different Temperatures and Oxygen Pressure (Thermal Evaporation법으로 제작한 ZnO 나노선의 온도와 산소유량에 따른 성장 특성)

  • Oh, Won-Seok;Jang, Gun-Eik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.8
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    • pp.766-769
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    • 2008
  • Zinc oxide (ZnO) nanowires were prepared on Si substrates by a thermal evaporation method at different temperatures and $O_2$ pressure. Microstructural analysis of the obtained ZnO nanowires was performed by using transmission electron microscopy(TEM) and scanning electron microscopy(SEM). Phase analysis was done using X-ray diffraction(XRD). As the deposition temperature and oxygen pressure were increased, the diameter and length of ZnO nanowires had a tendency to increase. Based on TEM and XRD analyses, the nanowires are single crystalline in nature and consist of a single phase. According to the measurements, the ZnO nanowires grown at 1100$^{\circ}C$, Ar 50 sccm, $O_2$ 10 sccm have good properties.

Evaporation Cooling of a Droplet containing a Surfactant (계면활성제를 첨가한 액적의 증발냉각)

  • Riu, Kap-Jong;Bang, Chang-Hoon;Kim, Hyun-Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.4
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    • pp.424-431
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    • 2003
  • The evaporation cooling phenomenon of a droplet containing a surfactant on a heated surface has been studied experimentally. The two kinds of heater modules made of brass and Teflon$^{TM}$ were tested to investigate the cooling characteristics of droplet. Solutions of water containing Sodium Lauryl Sulfate(0 ppm, 100 ppm, 1000 ppm) were tested in the experiments. The results showed that the contact angle decrease as the concentration of surfactant increases. The tendency did not very with different heated solid materials. As initial temperature of the heated surface becomes high, time averaged heat flux increases and evaporation time decreases with the denser concentration of surfactant. Therefore, water with denser concentration of surfactant could be effective to cool flammable materials. However, the effect of surfactant becomes low as the material temperature is higher than the boiling temperature of water.

Beat Transfer Analysis of Concrete Members under High Temperature (고온조건에서 콘크리트 부재의 온도전이)

  • Lee, Tae-Gyu;Kim, Hye-Uk
    • Proceedings of the KSR Conference
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    • 2009.05a
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    • pp.1536-1541
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    • 2009
  • When water inside the concrete member evaporates by high temperature, the evaporation heat which absorbs surrounding temperature occurs. The rate of increment of the internal temperature in concrete is reduced due to the evaporation heat in spite of continuously increasing external temperature. In this paper, the prediction method of internal temperature of high strength concrete members considering the evaporation heat under the high temperature is presented. Finite element method is employed to facilitate thermal analysis for any position of member. And the thermal characteristics models of high strength concrete affected by high temperature are proposed. To demonstrate the validity of this numerical procedure, the prediction by the proposed algorithm is compared with the test results of other researchers. The proposed algorithm shows a good agreement with the experimental results including the phenomenon that temperature is lost by the evaporation heat.

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