• Title/Summary/Keyword: evaporation characteristics

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Evaporation Heat Transfer Characteristics of Carbon Dioxide in the Inner Diameter Tube of 4.57 mm (4.57 mm 세관 열교환기 내 이산화탄소의 증발열전달 특성)

  • Ku, Hak-Keun
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.2
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    • pp.145-151
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    • 2007
  • The evaporation heat transfer coefficient of $CO_2$(R-744) in a horizontal tube was investigated experimentally. The main components or the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator(test section). The test section consists of a smooth, horizontal stainless steel tube of inner diameter of 4.57 mm. The experiments were conducted at mass flux of 200 to $500\;kg/m^2s$, saturation temperature of -5 to $5^{\circ}C$, and heat flux of 10 to $40\;kW/m^2$. The test results showed the heat transfer of $CO_2$ has a greater effect on nucleate boiling more than convective boiling. Mass flux of $CO_2$ does not effect nucleate boiling too much. In comparison with test results and existing correlations, the best fit of the present experimental data is obtained with the correlation of Jung et al. But existing correlations failed to predict the evaporation heat transfer coefficient of $CO_2$, therefore, it is necessary to develope reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

Evaporation Heat Transfer and Pressure Drop of R-22 and R-410A in Small Sized Micro-Fin Tubes (미소 전열촉진관내 R-22 및 R-410A의 증말열전달 및 압력강하 특성 연구)

  • Hwang, Junhyeon;Yun, Lin;Kim, Yongchan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.7
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    • pp.981-988
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    • 2001
  • Characteristics of evaporation heat transfer in 6.2 and 5.1mm OD micro-fin tubes were investigated in the present study. The data were taken at evaporation temperatures of -5$^{\circ}C$ and 5$^{\circ}C$ and heat fluxes 5kW/$m^2$ to 10kW/$m^2$. Mass flux was consequently maintained at 210, 300 and 410kg/$m^2$s for the 6.2mm OD tube and 465, 500 and 600kg/$m^2$s for the 5.1mm OD tube. The effects of heat flux, mass flux, and outer diameter on the heat transfer coefficient are explored in the present study. The data showed that the evaporation heat transfer coefficient for the 6.2mm OD tube was averagly higher by 16% than that for a 7.0mm OD tube, while the 5.1mm OD tube had approximately 30% higher value than the 6.2mm OD tube.

Effects of Hydrophilic Surface Treatment on Evaporation Heat Transfer at the Outside Wall of Enhanced Tubes (가공관의 외벽에서 친수성 표면처리가 증발열전달에 미치는 영향)

  • Park, No-Seong;Hwang, Gyu-Dae;Kim, Ho-Yeong;Gang, Byeong-Ha;Jeong, Jin-Taek
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.5
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    • pp.666-672
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    • 2001
  • Experiments have been carried out to investigate the evaporation heat transfer characteristics of various tubes on which hydrophilic surface treatment using plasma was employed. Spiral, corrugated and low-finned tubes were selected as test tubes. The evaporator tubes were bundled to form three rows of tubes connected in series, with each row being 400mm long. The results obtained indicate that hydrophilic treated tubes tested exhibit better evaporation heat transfer performance as compared with untreated tubes. It is found that the high wettability of the surface obtained through hydrophilic treatment induces film flow onto the tubes during the evaporation process, while sessile drops are formed on untreated tubes.

Characteristics of Thin Films Fabricated by Using the Layer-by-Layer Sputtering and Evaporation Method (순차 스퍼터 법과 증발 법으로 제작한 박막의 특성)

  • Cheon, Min-Woo;Park, Yong-Pil;Kim, Jeong-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.11a
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    • pp.571-574
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    • 2003
  • The thin films fabricated by using the layer-by-layer sputtering was compared with the thin film fabricated by using the evaporation method. Re-evaporation in the form of Bi atoms or $Bi_2O_3$ molecules easily bring out the deficiency of Bi atoms in thin film due to the long sputtering time of the layer-by-layer deposition. On the other hand, the respective atom numbers corresponding to BiSrCaCuO phase is concurrently supplied on the film surface in the evaporation deposition process and leads to BiSrCaCuO phase formation. Also, it is cofirmed that by optimizing the deposition condition, each single phase of the Bi2201 phase and the Bi2212 phase can be fabricated, the sticking coefficient of Bi element is clearly related to the changing of substrate temperature and the formation of the Bi2212 phase.

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Experimental Study on Effects of PAG Oil for $CO_2$ Evaporation Heat Transfer (PAG 오일이 $CO_2$ 증발열전달에 미치는 영향에 관한 실험적 연구)

  • Lee, Sang-Jae;Kim, Dae-Hoon;Choi, Jun-Young;Lee, Jae-Heon;Kwon, Young-Chul
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.5
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    • pp.357-363
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    • 2008
  • In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a horizontal micro-fin tube was performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($400{\sim}1200\;kg/m^2s$), heat fluxes($10{\sim}30\;kW/m^2$) and saturation temperatures ($-5{\sim}5^{\circ}C$), and PAG oil concentration($0{\sim}5\;wt%$). The variation of the heat transfer coefficient was different in accordance with the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

Effect of Defect Energy levels on the AC PDP Discharging Characteristics (MgO 보호막의 결함 전위 레벨이 AC-PDP 방전 특성에 미치는 효과)

  • Kwon, Sang-Jik;Kim, Yong-Jae;Cho, Eou-Sik
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.44 no.12
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    • pp.12-17
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    • 2007
  • The effects of the evaporation rate of MgO films using an electron beam on the MgO properties and the discharge characteristics of a plasma display panel(PDP) were investigated and analyzed. Mgo films were deposited with the various MgO evaporation rates. The MgO properties such as the crystal orientation, the surface roughness, and the film structure, were inspected using XRD(X-ray diffractometry), AFM(atomic force microscopy). From the experiments and Paschen law, the maximum value of the secondary, electron emission coefficient $(\gamma)$ was obtained at the evaporation rate of $5\AA/sec$. The minimum firing voltage and the maximum luminous efficiency were obtained at an evaporation rate of $5\AA/sec$. In the MgO film deposited at $5\AA/sec$, the (200) orientation and $F^+$ center were most intensive. The XRD results and cathode-luminescence(CL) spectra show the $\gamma$ values are correlated with $F/F^+$ centers of the molecular structure of MgO films.

Experimental Study on Characteristics of Evaporation Heat Transfer and Oil Effect of $CO_2$ in Mini-channels (미세채널 내 이산화탄소의 증발 열전달 특성 및 오일의 영향에 관한 실험적 연구)

  • Lee, Sang-Jae;Kim, Dae-Hoon;Choi, Jun-Young;Lee, Jae-Heon;Kwon, Young-Chul
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.1
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    • pp.16-22
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    • 2009
  • In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a mini-channels were performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($300{\sim}800kg/m^{2}s$), heat fluxes($10{\sim}40kW/m^2$) saturation temperatures($-5{\sim}5^{\circ}C$), and PAG oil concentration(0, 3, 5wt%). The variation of the heat transfer coefficient was different according to the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

Evaporation kent transfer characteristics of R-290 and R-600a in the horizontal tubes (수평관내 R-290과 R-600a의 증발 열전달 특성)

  • Son, Chang-Hyo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.2
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    • pp.264-269
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    • 2008
  • This paper presents the experimental results of evaporation heat transfer coefficients of HC(e.g. R290 and R600a), R-22 as a HCFCs refrigerant in horizontal double pipe heat exchangers, having four different inner diameters of 10.07 mm and 6.54 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 R-290 and R-600a was higher value than that of R-22. In comparison with R-22, the evaporation heat transfer coefficient of R-290 and 600a is approximately $56.7{\sim}70.1$ and $46.6{\sim}59.7%$ higher, respectively. In comparison with experimental data and some correlations, the evaporation heat transfer coefficients are well matched with the Kandlikar's correlation regardless of a type of refrigerants and tube diameters.

Analysis of the Impinging Spray Behavior Accompanying with Change of Phase (상변화를 동반한 충돌분무의 거동해석)

  • Song, Hong-Jong;Cha, Keun-Jong;Kim, Duck-Jool
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.6
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    • pp.852-859
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    • 2000
  • The emission in the exhaust gas from diesel engine is effected by the fuel spray characteristics. The spray of D.I. diesel engine impinges on a piston cavity and a cylinder wall. It is very important to know exactly the distribution and behavior of the spray inside cylinder. The objective of this study is to develop more accurate evaporation model. The EPISO code was used to analyze the flow characteristics in the engine. The Wakil model and the Faeth model are applied to the EPISO code to analyze the behavior of impinging spray. And also experimental and numerical analysis were carried out. The spray behavior characteristics were investigated by changing injection pressure, ambient pressure and temperature. The behavior of impinging spray was strongly effected by the change of ambient pressure and temperature. The effects of evaporation and rebounding droplet should be considered.

Effects of Evaporation on the Weathering Rate and Chemical Composition of Iranian Heavy Crude Oil (이란산 원유의 증발에 따른 풍화율 및 화학적 성상 변화)

  • Kim, Beom;Kim, Gi-Beum;Sim, Won-Joon;Yim, Un-Hyuk
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.15 no.3
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    • pp.238-246
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    • 2012
  • Once oil is spilled into marine environment, it experiences various weathering processes among which evaporation is the most dominant process in the initial stage of weathering. This study aimed to elucidate the effects of evaporation on the physicochemical properties of spilled oil using standardized laboratory experiments. Laboratory evaporation process was successfully reproduced using controlled rotary evaporation method. In case of Iranian Heavy crude (IHC), evaporation rate after 48 hours was $29.3{\pm}0.4%$ (n=40, p<0.001). Evaporation was simulated using ADIOS2 weathering model and the result was in agreement with laboratory experiment. Chemical composition changes of petroleum hydrocarbons including alkanes, polycyclic aromatic hydrocarbons (PAHs) and biomarkers by evaporation rate were also analyzed. As oil evaporated, low molecular weight alkanes and PAHs decreased, while biomakers showed conservative characteristics. Among biomarkers, $17{\alpha}(H)$, $21{\beta}(H)$-hopane was used for calculation of weathering rates, which matched with evaporative mass losses. Weathering rate calculation using hopane showed that stranded oils of weathering stage I (28.9%) and mesocosm oil weathering experiment till 5 days (26.5%) were mainly affected by evaporation process.