• 제목/요약/키워드: evaporation characteristics

검색결과 926건 처리시간 0.026초

Preparation and Characteristics of $CdS_{1-x}Te_{1-x}$ Ternary Polycrystalline Thin Films by Co-evaporation (동시 열증착법에 의한 $CdS_{1-x}Te_{1-x}$ 삼원계 다결정 박막의 제작과 특성)

  • 박민서;송복식;정성훈;문동찬;김선태
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 한국전기전자재료학회 1995년도 추계학술대회 논문집
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    • pp.126-130
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    • 1995
  • $CdS_{1-x}Te_{1-x}$ polycrystalline thin films were fabricated from CdS and CdTe powder by co-evaporation method at $10^{-6}$ Torr. The Optimum evaporation condition was substrate temperature $T_{s}$=$150^{\circ}C$, evaporation time t=30 min. XRD spectrums indicated that the crystal structure chanced from zinc blonde (x$\leq$0.22) to wurtzite (x$\geq$0.96) through mixed structure (0.22$\leq$0.74) as composition value x increase to CdS. Conductive type was n-type by hot point probe method. van der Pauw method was not applicable for x<0,5 due to high hall voltages, Electrical resistivity and Hall carrier mobility were decreased as x increase, while Hall carrier concentration was increased. The optical bandgap of $CdS_{1-x}Te_{1-x}$ polycrystalline thin films measure d at R.T. had quardratic form and the bowing parameter was fitted as 1.98eV for theoretical value of 2.0eV. I-V characteristics of In/CdTe/$CdS_{x}Te_{1-x}$Au Schottky diodes showed that CdS-rich one had better forward characteristics than CdTe-rich one.

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A Study on Evaporation Characteristics and Concentration Distribution of LPG fuel using Light Extinction Method (광흡수법을 이용한 LPG 연료의 증발특성 및 연료 농도 분포에 관한 연구)

  • Kim, D.K.;Cho, G.B.;Oh, S.M.;Choi, K.N.;Jeong, D.S.
    • Proceedings of the KSME Conference
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    • 대한기계학회 2001년도 춘계학술대회논문집D
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    • pp.708-714
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    • 2001
  • Although LP gas has lots of advantages, there has been limitation in application for automotive engine due to the several disadvantages, such as power decrease, complex fuel supply unit, and back fire etc. However LP gas direct injection engine has possibility to solve the problems above mentioned. LEM(Light Extinction Method) was employed for analysis of spacial and temporal distribution of LP gas which is directly injected into combustion chamber under various pressure and temperature conditions. The results from CVC(Constant Volume Chamber) were compared to those of RICEM(Rapid Induction, Compression and Expansion Machine) which simulate early- and late injection of direct injection engine. LPG fuel spray is affected by temperature and pressure in evaporation characteristics but it is more benefit to direct injection engine in every way such as, fuel distribution, evaporating speed and well wetting reduction.

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A Study on the Surface Characteristics of MgO Layer as the Various Deposition Methods of Electron-beam Evaporation (Electron-beam Evaporation의 증착 방법에 따른 MgO Layer의 표면 특성에 관한 연구)

  • Heo, Jeong-Eun;Lee, Don-Kyu;Cho, Sung-Yong;Lee, Hae-June;Lee, Ho-Jun;Park, Chung-Hoo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • 제21권5호
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    • pp.468-473
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    • 2008
  • A MgO layer is used as electrode protective film in the alternating current plasma display panel (AC PDP). The properties of MgO layer are thought to be one of the most important factors that affects the panel reliability through the firing voltage variation. In this study, we investigated the relations between the surface characteristics and e-beam evaporation process parameters such as deposition rate, temperature of substrate and distance between the MgO pellet and substrate. To produce the MgO layer of (200) crystal orientation, we suggest the high temperature of the substrate, the long distance between the pellet and substrate and the high deposition rate.

Electrical Characteristics of Organic Light-emitting Diodes Fabricated by Varying a Hole-size in Evaporation Boat

  • Kim, Weon-Jong;Park, Young-Ha;Cho, Kyung-Soon;Hong, Jin-Woong;Shin, Jong-Yeol;Kim, Tae-Wan
    • Transactions on Electrical and Electronic Materials
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    • 제9권3호
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    • pp.105-109
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    • 2008
  • Electrical characteristics of organic light-emitting diodes were investigated by varying a hole-size in evaporation boat in the device structure of ITO/tris(8-hydroxyquinoline) aluminum$(Alq_3)$/Al. The device was manufactured using a thermal evaporation under a base pressure of $5{\times}10^{-6}$ Torr. The $Alq_3$ emitting organics were evaporated to be a thickness of 100 nm at a deposition rate of $1.5{\AA}/s$. A cylindrical-shaped evaporation boat was made out of stainless steel with a small size of hole on top of the boat. Several evaporation boats were made having a different hole size on top; 0.8 mm, 1.0 mm, 1.5 mm, and 3.0 mm. We found that when the hole size on top of the evaporation boat is 1.0 mm, the average roughness is rather smoother compared to the other ones. Also, luminance and external quantum efficiency are superior to the others. Compared to the ones from the devices made with the hole-size of 0.8 mm boat. The luminance and external quantum efficiency of the device made with the hole-size of 1.0 mm boat were improved by a factor of seventy and thirty three, respectively. Also operating voltage is reduced to 2 V.

A Study on the Acquisition Technique of Water Retention Characteristics Based on the Evaporation Method and the Chilled Mirror Method for Unsaturated Soils (증발법과 냉각거울법에 의한 불포화토의 함수특성 획득기법 연구)

  • Oh, Seboong;Yoo, Younggeun;Park, Gyusoon;Kim, Seongjin
    • Journal of the Korean GEO-environmental Society
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    • 제23권4호
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    • pp.11-20
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    • 2022
  • In order to acquire hydraulic characteristics for unsaturated layers, water retention tests were performed and compared by using the evaporation method, volumetric pressure plate extractor (VPPE) and chilled-mirror dew point method. The evaporation and chilled-mirror method are currently developed experimental technology and measure the water retention curve of unsaturated soils quickly and accurately. In the evaporation and VPPE method, the water retention has been measured and compared until 100kPa matric suction and consequently the result of the evaporation method could be verified. In the chilled-mirror method, the water retention has been measured until high level of matric suction and the overall shape of water retention curves could be obtained. As a result of water retention tests, the representative water retention curves were obtained and the applicability of each test method was discussed. Using both the evaporation and chilled-mirror methods, the soil water retention curve can be acquired reasonably for the whole range of matric suction.

Numerical study of heat and mass transfer around an evaporative condenser tube by multi-zone method (다중 영역법을 이용한 증발식 응축관 주위의 열 및 물질전달 해석)

  • ;;Yun, In-Chul;Yoo, Je-In
    • Transactions of the Korean Society of Mechanical Engineers
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    • 제19권12호
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    • pp.3317-3328
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    • 1995
  • The objective of the present study is to predict the characteristics of heat and mass transfer around an evaporative condenser. Numerical calculations have been performed using multi-zone method to investigate heat transfer rate and evaporation rate with the variation of inlet condition(velocity, relative humidity and temperature) of the moist air, the flow rate of the cooling water and the shape of the condenser tube. From the results it is found that the profile of heat flux is the same as that of evaporation rate since heat transfer along the gas-liquid interface is dominated by the transport of latent heat in association with the vaporization(evaporation) of the liquid film. The evaporation rate and heat transfer rate is increased as mass flow rate increases or relative humidity and temperature decrease respectively. But the flow rate of the cooling water hardly affect the evaporation rate and heat flux along the gas-liquid interface. The elliptic tube which the ratio of semi-minor axis to semi-major axis is 0.8 is more effective than the circular tube because the pressure drop is decreased. But the evaporation rate and heat flux shown independency on the tube shape.

Condensation and evaporation heat transfer characteristics of HFC-134a in a horizontal smooth and a micro-finned tube (수평 평활관과 마이크로핀 관내에서 HFC-134a의 응축 및 증발열전달 특성)

  • Lee, Sang-Cheon;Park, Byeong-Deok;Han, Un-Hyeok;Lee, Jae-Hui
    • Transactions of the Korean Society of Mechanical Engineers B
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    • 제20권5호
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    • pp.1725-1734
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    • 1996
  • Experimental condensation and evaporation heat transfer coefficients were measured in a horizontal smooth tube and a horizontal micro-finned tube with HFC-134a. The test sections are straight, horizontal tubes with have a 9.52mm outside diameter and about 5000mm long. The micro-finned tube had 60 fins with a height of 0.12mm and a spiral angle of 25.deg.. The condensation test section was a double-pipe type with counter flow configuration. The evaporation test section employed an electic heating method. Enhancement factors which is defined as a ratio of the heat transfer coefficient for micro-finned tube to that for smooth tube, varied from 1.3 to 1.6(mass flux:110~190kg/m$^{2}$s) for condensation and 1.2 to 1.5 (mass flux:70~160kg/m$^{2}$s) for evaporation. The experimental data of condensation and evaporation heat transfer coefficients were compared to several empirical correlations. Based on these comparisons, modified correlations of the condensation and evaporation heat transfer coefficient for both smooth and micro-finned tubes were proposed.

Evaporation Heat Transfer Characteristics of Hydrocarbon Refrigerants R-290 and R-600a in the Horizontal Tubes

  • Roh, Geon-Sang;Son, Chang-Hyo;Oh, Hoo-Kyu
    • Journal of Advanced Marine Engineering and Technology
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    • 제31권1호
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    • pp.74-83
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    • 2007
  • This paper presents the experimental results of evaporation heat transfer coefficients of HC refrigerants (e.g. R290 and R600a). R-22 as a HCFCs refrigerant and R-l34a as a HFCs refrigerant in horizontal double pipe heat exchangers, having four different inner diameters of 10.07, 7.73, 6.54 and 5.80 mm respectively. The experiments of the evaporation process were conducted at mass flux of $35.5{\sim}210.4 kg/m^2s$ and cooling capacity of $0.95{\sim}10.1 kW$. The main results were summarized as follows : The average evaporation heat transfer coefficient of hydrocarbon refrigerants(R-290 and R-600a) was higher than the refrigerants, R-22 and R-l34a. In comparison with R-22 the evaporation heat transfer coefficient of R-l34a is approximately $-11{\sim}8.1 %$ higher. R-290 is $56.7{\sim}70.1 %$ higher and R-600a is $46.9{\sim}59.7 %$ higher. respectively. In comparison with experimental data and some correlations, the evaporation heat transfer coefficients are well predicted with the Kandlikar's correlation regardless of a type of refrigerants and tube diameters.

Droplet Evaporation on Surf aces of Various Wettabilities (다양한 습윤성 표면 위에서의 액적 증발)

  • Song, Hyun-Soo;Lee, Yong-Ky;Jin, Song-Wan;Kim, Ho-Young;Yoo, Jung-Yul
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2008년도 춘계학술대회논문집
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    • pp.662-665
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    • 2008
  • We experimentally investigate the evaporation characteristics of water droplet on surfaces of various wettabilities in the range of contact angle from 30$^{circ}$ to 150$^{circ}$. When a liquid droplet on a solid surface evaporates, the contact angle generally decreases with time and the evaporation rate varies with the droplet geometry such as the contact angle and the radius of curvature. Experimental data on the contact angle as a function of the droplet volume obtained by digital image analysis techniques cannot be explained by the existing theories. By measuring the temporal evolutions of the droplet radius and contact angle, we find the qualitative difference between the evaporation patterns on the hydrophilic surfaces where the contact radius remains constant initially and those on the superhydrophobic surfaces where the contact angle remains constant. Also, the evaporation rate is observed to depend on the surface material although the currently available models assume that the rate is solely determined by the droplet geometry. Despite the fact that the theory to explain this dependence on the surface remains to be pursued by the future work, we give the empirical relations that can be used to predict the droplet volume evolution for each surface. It is expected that the present study will contribute to interpreting the effect of droplet geometry on the evaporation.

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Experimental Study on Evaporation Heat Transfer and Oil Effect in Micro-fin Tube Using $CO_2$ (마이크로핀관 내 $CO_2$의 증발 열전달과 오일 영향에 관한 실험적 연구)

  • Lee, Sang-Jae;Choi, Jun-Young;Lee, Jae-Heon;Kwon, Young-Chul
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • 제20권2호
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    • pp.106-112
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    • 2008
  • In this paper, the experimental results on evaporation heat transfer characteristics were reported for a micro-fin tube using $CO_2$. An experimental refrigerant loop had been established to measure the evaporation heat transfer coefficient and pressure drop of $CO_2$. Experiments were conducted for mass fluxes, heat fluxes, saturation temperatures and PAG oil concentrations. With increasing the heat flux and the saturation temperature, the evaporation heat transfer coefficient increased. At the higher mass flux, however, the exit vapor quality of the micro-fin tube was to be lower. The peak of the heat transfer coefficient was shifted toward low quality region. The evaporation pressure drop increased as the mass flux increased and the saturation temperature decreased. As PAG oil concentration increased, the evaporation heat transfer coefficient decreased and the dryout was delayed by oil addition.