• Journal of Advanced Marine Engineering and Technology
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• 제29권3호
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• pp.297-305
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• 2005

The evaporation heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of 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 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500\;kg/m^{2}s$. saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$. and heat flux of 10 to $40\;kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has greatly effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality. heat flux and saturation temperature. The evaporation heat transfer coefficient of $CO_2$ is very larger than that of R-22 and R-134a. In making a comparison between test results and existing correlations. the present experimental data are the best fit for the correlation of Jung et al. But it was failed to predict the evaporation heat transfer coefficient of $CO_2$ using by the existing correlation. Therefore. it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.189-196
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• 2007

The evaporation heat transfer coefficient and pressure drop of $CO_2$(R-744) in a horizontal tube was investigated experimentally. The main components of the experimental apparatus are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and an evaporator(test section). The test section consists of a horizontal stainless steel tube of 4.57 mm inner diameter. The experiments were conducted at mass flux of $200{\sim}1000\;kg/m^2s$ saturation temperature of $0{\sim}20^{\circ}C$, and heat flux of $10{\sim}40\;kW/m^2$. The test results showed that the heat transfer coefficient of $CO_2$ has a greater effect on nucleate boiling more than convective boiling. Mass flux of $CO_2$ does not affect nucleate boiling too much. In comparison with test data and existing correlations, All of the existing correlations for the heat transfer coefficient underestimated the experimental data. However lung et al.'s correlation showed a good agreement with the experimental data. The evaporation pressure drop of $CO_2$ increases with increasing mass flux and decreasing saturation temperature. When comparison between the experimental pressure drop and existing correlations. Existing correlations failed to predict the evaporation pressure drop of $CO_2$.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.827-834
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• 2009

The cooling heat transfer coefficient of $CO_2$ in a brazing type small diameter tube was investigated experimentally. The main components of the refrigerant loop are a receiver, a $CO_2$ compressor, a mass flow meter, an evaporator and a brazing type small diameter tube as a test section. The mass flux of $CO_2$ is $400{\sim}1600$ [kg/$m^2s$], the mass flowrate of coolant were varied from 0.15 to 0.3 [kg/s], and the cooling pressure of gas cooler were from 8 to 10 [MPa]. The cooling heat transfer coefficients of the brazing type small diameter copper tube is about $4{\sim}11.7%$ higher than that of the conventional type small diameter copper tube. In comparison with test results and existing correlations, correlations failed to predict the cooling heat transfer coefficient of $CO_2$ in a brazing type small diameter copper tube. therefore, it is necessary to develope reliable and accurate predictions determining the cooling heat transfer coefficient of $CO_2$ in a brazing type small diameter copper tube.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.241-246
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• 2007

The present paper dealt with an experimental study of boiling heat transfer characteristics of $CO_2$. Heat transfer coefficients of the refrigerant flow inside horizontal smooth microchannel were obtained with inner tube diameter of 0.3mm and length of 300mm. The direct electric heating method was applied for supplying the heat uniformly to the refrigerant. The experiments were conducted with $CO_2$ purity of 99.99%, at saturation temperature of $10^{\circ}C$, mass flux ranges of $300{\sim}900\;kg/m^2s$, and heat flux ranges of $15{\sim}45\;kW/m^2$. While heat transfer coefficient increased with the increase of heat flux in the low quality region, the heat transfer coefficient decreased with the increase of quality in the high quality region. The heat transfer coefficients were compared with seven existing correlations with the Gungor-Winterton's(1986) correlation gave the best prediction. A new corelation to predict the two-phase flow heat transfer coefficient was developed based on the Chen(1966) correlation. The new correlation predicted the experimental data well with a mean deviation of 9.69% and average deviation of -3.03%.

• 한국디지털건축인테리어학회논문집
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• 제12권2호
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• pp.67-76
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• 2012

BIM and its quantity take-off widely apply to the construction projects and LCCO2 Assessment using the BIM's quantity take-off function can be tried recently. Because BIM modeling programs such as Revit and ArchiCAD do not provide adequate library for LCCO2 Assessment, quantity take-off data should be conversed and applied to Carbon Emission Coefficient using Excel program or manual work. Therefore, the purpose of this research is 1) to propose the Unit Conversion Systems for Carbon Emission Coefficient, 2) to provide basic library sets for BIM based LCCO2 Assessment method, and 3) to apply 11 material library sets on a apartment unit plan modeling to pursue the CO2 emission evaluation of the material production in the process of LCCO2 Assessment. Research results showed CO2 emission amount of 458.64kgCO2/m2 from the apartment unit plan modeling.

• 설비공학논문집
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• 제25권5호
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• pp.233-239
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• 2013

The Thermophysical properties of thermal conductivity, viscosity, and heat capacity for $CO_2$ slurry ($CO_2$ gas and $CO_2$-hydrate mixture) having a high gas phase volume fraction were predicted using the conventional mixture models and the TRAPP model under hydrate formation conditions. Based on the calculated thermophysical properties, the heat transfer coefficient and pressure drop of the $CO_2$ slurry in the tube were predicted. The thermal conductivity of $CO_2$ slurry ranged from 0.02 to 0.2 W/m-K, and the mixture viscosity was larger than that of pure $CO_2$ by 1.9~2.7 times. The heat capacity of $CO_2$ slurry ranged from 63 to 68% of that for pure $CO_2$. The predicted heat transfer coefficient of $CO_2$ slurry was 6 times higher than that of pure $CO_2$. In the separate model, the estimated pressure drop increased with an increase of $CO_2$-hydrate mole fraction, and was 60% of that of pure $CO_2$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.3.2-3.2
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• 2005

• 콘크리트학회논문집
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• 제22권2호
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• pp.209-217
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• 2010

최근 콘크리트의 탄산화 진행 예측을 위한 수식적 모델들이 보고되고 있으며, 이러한 모델들은 $Ca(OH)_2$과 $CO_2$의 화학적 반응과 $CO_2$의 확산에 대한 관계를 연구하고 있다. 이 모델들은 콘크리트의 탄산화 영역에서 $CO_2$가 확산하고 콘크리트 중의 탄산화 영역과 미탄산화 영역과의 경계면에서 $Ca(OH)_2$와 반응한다는 가정에 기초하고 있다. 이 연구에서는 콘크리트중의 $CO_2$ 확산 및 탄산화진행영역에서의 $CaCO_3$와 $Ca(OH)_2$의 공존을 고려한 $CO_2$와 $Ca(OH)_2$와의 반응을 모델화한 것이다. 콘크리트 탄산화진행을 보다 정확하게 표현하기 위해 콘크리트 투기계수로서 탄산화진행모델에 적용하여 $CO_2$확산 계수를 유추하였다. 모델에 의한 예측은 W/C에 따라 페인트처리를 실시한 콘크리트의 촉진탄산화의 실험 결과와 아주 유사하게 나타나, 콘크리트 투기계수를 이용한 탄산화 진행속도 기본방정식을 활용하여 촉진환경 및 일반 대기환경에서 탄산화 진행예측이 가능함으로서 철근콘크리트구조물의 내구성설계를 위한 보다 정량적인 수명예측이 가능할 것으로 사료된다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 추계종합학술대회
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• pp.796-799
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• 2002

BSCCO thin films are fabricated via a co-deposition process at an ultra-low growth rate using ion beam sputtering. The sticking coefficient of Bi element exhibits a characteristic temperature dependence. This temperature dependence of the sticking coefficient was explained consistently on the basis of the evaporation and sublimation processes of Bi$_2$O$_3$.

• 설비공학논문집
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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.