• 설비공학논문집
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• 제14권1호
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• pp.73-82
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• 2002

A small refrigeration system used in a water purifier was tested by employing propane/isobutane (R-290/R-6OOa) mixtures as an alternative refrigerant of R-12. The drop-in tests were performed by varying mass fraction of propane at 0.25, 0.5 and 0.75 with a change of both refrigerant charge amount and capillary tube length in order to find an optimum composition in aspect of performance and reliability of the system. As a result, the mixture of 50% propane-50% isobutane showed the best performance and reliability among them in a small refrigeration system. During steady state operations, both the COP and refrigeration capacity increased by 4% and 9%, respectively, as compared to the baseline R-12 system. In addition, the propane/isobutane (50/50) mixture system yielded advantages in the minimization of modification and redesigning of system components due to very similar saturation tempera- ture and pressure characteristics with R-12.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.399-408
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• 2006

Nucleate pool boiling heat transfer coefficient (HTCs) were measured with one nonazeotropic mixture of propane/isobutane and two azeotropic mixtures of HFC134a/isobutane and propane/HFC 134a. All data were taken at the liquid pool temperature of $7^{\circ}C$ on a horizontal plain tube of 19.0mm outside diameter with heat fluxes of $10\;kW/m^2\;to\;80kW/m^2$ with an interval of $10\;kW/m^2$ in the decreasing order of heat flux. The measurements were made through electrical heating by a cartridge heater. The nonazeotropic mixture of propane/isobutane showed a reduction of HTCs as much as 41% from the ideal values. The azeotropic mixtures of HFC134a/isobutane and propane/HFC134a showed a reduction of HTCs as much as 44% from the ideal values at compositions other than azeotropic compositions. At azeotropic compositions, however, the HTCs were even higher than the ideal values due to the increase in the vapor pressure. For all mixtures, the reduction in heat transfer was greater with larger gliding temperature difference. Stephan and Korner's and lung et al's correlations predicted the HTCs of mixtures with a mean deviation of 11%. The largest mean deviation occurred at the azeotropic compositions of HFC134a/isobutane and propane/HFC134a.

• 대한수의학회지
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• 제22권2호
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• pp.111-114
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• 1982

In order to explore more efficient protein substitutes by improving the utilization of non-protein nitrogen compounds in ruminants, the experiment was undertaken. The effects of sulfur coated urea (SCU) and diuredio isobutane (DUIB) in the ruminal fluid on the concentration of $NH_3-N$, the total count of the ruminal ciliates and pH value were estimated in vitro. The results obtained from the experiment were as follows: 1. The pH of the media of the group added diuredio isobutane and sulfur costed urea tends to decrease slightly at 9 hours after the incubation, but no pH changes were observed in the media added urea alone. 2. The number of the ciliates in the ruminal fluid was slightly increased 9 hours after the incubation in all groups. 3. The concentrations of $NH_3-N$ in the ruminal fluid were gradually increased according to the incubation in vitro showing 418, 431 and $627{\mu}g/ml$ in the group added diuredio isobutane and 428, 569 and $792{\mu}g/ml$ in the group added sulfur coated urea at 0, 0.5 and 9 hours after the incubation, respectively.

• 설비공학논문집
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• 제18권12호
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• pp.955-963
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• 2006

Nucleate pool boiling heat transfer coefficients (HTCs) were measured with one nonazeotropic mixture of Propane/Isobutane and two azeotropic mixtures of HFC134a/Isobutane and Propane/HFC134a. All data were taken at the liquid pool temperature of $7^{\circ}C$ on a horizontal plain tube with heat fluxes of $10kW/m^2\;to\;80kW/m^2$ with an interval of $10kW/m^2$ in the decreasing order of heat flux. The measurements were made through electrical heating by a cartridge heater. The nonazeotropic mixture of Propane/Isobutane showed a reduction of HTCs as much as 41% from the ideal values. The azeotropic mixtures of HFC134a/Isobutane and Propane/HFC134a showed a reduction of HTCs as much as 44% from the ideal values at compositions other than azeotropic compositions. At azeotropic compositions, however, the HTCs were even higher than the ideal values due to the increase in the vapor pressure. For all mixtures, the reduction in heat transfer was greater with a larger gliding temperature difference. Stephan and $K{\ddot{o}}rner's$ and Jung et al's correlations predicted the HTCs of mixtures with a mean deviation of 11%. The largest mean deviation occurred at the azeotropic compositions of HFC134a/Isobutane and Propane/HFC134a.

• 공업화학
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• 제22권6호
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• pp.587-593
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• 2011

대기환경 규제와 자동차 성능 유지 등 고급 가솔린인 알킬레이트 생산공정에 대한 관심이 높아지고 있다. 알킬레이트는 이소부탄과 올레핀의 알킬레이션 반응을 통해서 생산된다. 하지만 기존의 공정에서 사용되고 있는 불산이나 황산의 유해성으로 인하여 새로운 친환경 촉매에 대한 연구가 활발히 진행되고 있다. 최근 기존의 고체산 촉매인 제올라이트 이외에 메조기공 촉매 및 이온성액체를 이용한 연구가 수행되고 있다. 본 논문에서는 이소부탄 알킬레이션 공정을 위한 친환경 촉매에 대한 논하려 한다.

• Bulletin of the Korean Chemical Society
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• 제5권1호
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• pp.16-21
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• 1984

The relative Arrhenius parameters for t-butoxy radical decomposition (log $A_d$, $E_d$) and hydrogen abstraction of t-butoxy radical from hydrogen donor (log $A_d$, $E_d$) by competitive method were obtained as follows: for cyclohexane; log $A_a/A_d$ = -4.17 mole/l and $E_d-E_a$ = 9.01 kcal/mole, for isobutane; log $A_a/A_d$ = -5.70 mole/l and $E_e-E_a$= 11.0 kcal/mole. From the reported Arrhenius parameters for t-Butoxy radical decomposition reactions the parameters for t-Butoxy radical reactions with isobutane and cyclohexane are estimated to be log $A(l/mol{\cdot}sec)$ = 8.4, $E_a$ = 4.3 kcal/mol and $log A (l/mol{\cdot}sec)= 9.9,\;E_a$ = 6.3 kcal/mol, respectively.

• 설비공학논문집
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• 제19권7호
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• pp.545-554
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• 2007

Flow condensation heat transfer coefficients(HTCs) of R22, propylene, propane, DME and isobutane are measured on a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 mm outside diameter and 530 mm length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed refrigerant saturation temperature of $40{\pm}0.2^{\circ}C$ with mass fluxes of 100, 200, $300kg/m^2s$ and heat flux of $7.3\sim7.7kW/m^2$. The data are obtained in the vapor Quality range of $10\sim90%$. Test results show that at same mass flux the flow condensation HTCs of propylene, propane, DME and isobutane are higher than those of R22 by up to 46.8%, 53.3%, 93.5% and 61.6% respectively. Also well-known correlations developed based upon conventional fluorocarbon refrigerants predict the present data within a mean deviation of 30%. Finally, the pressure drop increase as the mass flux and Quality increase and isobutane shows the highest pressure drop due to its lowest vapor pressure among the fluids tested.

• 공업화학
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• 제26권3호
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• pp.347-350
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• 2015

본 논문에서는 친환경 촉매 중 하나인 이온성액체를 이용한 이소부탄 알킬레이션 반응에 대해서 연구하였다. 산성 이온성액체 중 하나인 1-Octyl-3-methylimidazolium-bromide-aluminum chloride를 촉매로 사용하였다. 최적의 반응조건을 규명하기 위하여 액체공간속도, 반응온도 및 이온성액체의 조성에 따른 반응성능에 대하여 조사하였다. 일정한 실험 조건에서 반응온도의 경우 $80^{\circ}C$에서 최적의 반응성능을 보였고 이온성액체의 조성은 음이온 비가 0.56인 경우 우수한 반응특성을 보였다. 또한 반응조건에 따른 생성물의 수율을 예측할 수 있는 모델식을 통계학적 접근을 통해 완성하였다.

• 대한기계학회논문집B
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• 제29권2호
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• pp.271-278
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• 2005

In this paper, the performance of Kim-chi refrigerator with three evaporator and one compressor was investigated in employing $55\%$ propane and $45\%$ isobutane (R290/R600a) refrigerant mixture as an alternative refrigerant of R134a. The drop-in test was performed by varying both refrigerant charge and capillary tube length in order to find both the performance and reliability of a small multi-refrigeration system. Results show that the power consumption is decreased by about $15\%$ and COP is increased by about $10\%$, respectively as compared to the baseline system using R-134a. In addition, the propane/isobutane refrigerant mixture system took advantage of the minimization of modification and redesigning of system components because thermodynamic properties such as saturation pressure, temperature, normal boiling point(NBP) characteristics are similar to those of R134a. The reduction of sales cost is caused by the decrease of refrigerant cost per unit mass and refrigerant charge amount necessary for the refrigeration system.

• 대한화학회지
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• 제55권5호
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• pp.812-818
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• 2011

[ $V_{0.9}Sb_{0.1}O_x$ ]systems, bulk and deposited on different supports (five types of ${\gamma}$-aluminas, ${\alpha}$-alumina, silica-alumina, silica gel, magnesium oxide), have been tested in the oxidative dehydrogenation (ODH) of iso-butane. This statement is derived from the data obtained by a set of characterisation techniques(specific surface area measurements, X-ray diffraction, X-ray photoelectron spectroscopy, laser Raman spectroscopy, in situ differential scanning calorimetry and in situ diffuse reflectance-absorption infrared Fourier transform spectroscopy).