• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.681-691
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• 2006

Nucleate boiling heat transfer for refrigerants, R113, and R113+wt4% ethanol mixture, an azeotropic mixture under electric field was investigated experimentally in a single-tube shell/ tube heat exchanger. A special electrode configuration which provides a more uniform electric field that produces more higher voltage limit against the dielectric breakdown was used in this study. Experimental study has revealed that the electrical charge relaxation time is an important parameter for the boiling heat transfer enhancement under electric field. Up to 1210% enhancement of boiling heat transfer was obtained for R113+wt4% ethanol mixture which has the electrical charge relaxation time of 0.0053 sec whereas only 280% enhancement obtained for R113 which has relaxation time of 0.97 sec. With artificially machined boiling surface, more enhancement in the heat transfer coefficient in the azeotropic mixture was obtained.

• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.395-400
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• 2007

Ambient drying sol-gel processing was used for monolithic silica ambigels in the temperature range of $130-250^{\circ}C$. A new method of mesopore ambigels, which mean the aerogels prepared by ambient pressure drying process synthesis, is suggested at first. This method includes two important approaches. The first point is that $SiO_{2}$ surface modification of wet gel was performed by trimethylchlorosilane in n-butanol solution. This procedure is provided the silica gel mesopore structure formation. The second point is a creation of the ternary azeotropic mixture water/n-butanol/octane as porous liquid, which is effectively provided removing of water such a low temperature by 2 step drying condition under ambient pressure. The silica aerogels, which were prepared by ambient pressure drying from azeotropic mixture of water/n-butanol/octane, are transparent, crack-free and mesoporous (pore size ${\sim}$ 5.6 nm) with surface area of ${\sim}$ $923{\;}m^2/g$, bulk density of $0.4{\;}g/cm^3$ and porosity of 85 %.

• Journal of Mechanical Science and Technology
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• v.20 no.3
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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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.1125-1133
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• 1995

Experiments were performed to investigate the condensing heat transfer characteristics of non-azeotropic mixtures of R-22 and R-114 in a heat pump system with a horizontal smooth tube as a condenser. The ranges of parameters, such as heating capacity, mass flow rate of refrigerant and quality were 780-3,480W, 24-71kg/h, and 0-1, respectively. The overall compositions of R-22 in a R-22/114 mixture were 25, 50, 75 and 100 per cent by wight. The results show that the overall condensing heat transfer coefficients for the mixtures were lower than the pure R-22 values. Local heat transfer coefficient of the pure R-22 was hghest at the top of the test tube. The local heat transfer coefficient of R-22/114 (50/50 wt%) at side and bottom of the test tube was higher than that at the top. From the obtained data, a prediction for the condensing heat transfer coefficients of the mixture was done based on the method of Fujii.

• 연구논문집
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• s.25
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• pp.77-90
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• 1995

For improving performance of heat pump system, researcher has adapted 2-stage economizer cycle and developed a high-efficiency screw compressor, new working medium(non-azeotropic mixed refrigerant) and counterflow heat exchangers operating with a small temperature difference. Target of this study is development of high performance heat pump system with the 2-stage economizer system using the non-azeotropic mixed refrigerant. For the purpose of excuting target, we constucted computer simulation programs, compared and examed various types of cycle and non-azeotropic mixture. Based on the results from computer simulation we selected optimum mixtures and reflected design and production process of performance test equipment with the 1-stage econmizer system. In order to accomplish the final target, design and production of the 2-stage economizer system, we performed pilot test using the 1-stage economizer performance test system and finally design and production of the 2-stage economizer system.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.255-265
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• 2018

The huge amount of solvents used in the semi-conductor and display industry typically result in waste of valuable solvents which often form complex azeotropic mixtures. This study explored a recovery process of a quaternary waste solvent, comprising methyl 2-hydroxybutyrate, propylene glycol monomethyl ether acetate, ethyl lactate, and ethyl-3-ethoxy propionate. In this study, a novel shortcut column method with a graphical approach was exploited for the distillation column design of complex quaternary azeotropic mixtures. As a result, the proposed shortcut method and design procedure solved the complex separation paths successfully with less computational efforts while achieving all requirements for component purity.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.307-313
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• 2014

In this study, an optimization process design has been performed to separate 99.9 mol% of Isobutyl Acetate from binary azeotropic mixture of Isobutyl Acetate and Isobutyl Alcohol system using a Pressure Swing Distillation (PSD). PSD is used to separate binary azeotropic mixtures using the difference between the relative volatilities and azeotropic compositions by changing the system pressure. Non-Random Two Liquid (NRTL) model for liquid phase and the Peng-Robinson equation for vapor phase are used. An optimization study for the reflux ratio and feed stage locations which minimize the total reboiler heat duties are studied. Since PSD process consists of two columns, i.e. high pressure and low pressure, the effect of column sequence on the optimum conditions is reported.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.225-233
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• 1995

Experiments were performed to investigate the heat transfer characteristics of nonazeotropic mixture R-22+R-114 in a heat pump system. The ranges of parameter, such as heat flux, mass flow rate, and quality were $8,141{\sim}32,564W/m^2$, 24~58kg/h, and 0~1, respectively. The overall compositions of the mixtures were 50 and 100 per-cent of R-22 by weight for R-22+R-114 mixture. The results indicated that there were distinct different heat transfer phenomena between the pure substance and the mixture. In case of pure refrigerant the heat transfer rates for cooling were strongly dependent upon quality of the refrigerant. Overall evaporating heat transfer coefficients for the mixture were somewhat lower than pure R-22 values in the forced convective boiling region. For a given flow rate, the heat transfer coefficient at the circumferential tube wall(top, side, and bottom of the test tube) for R-22/R-114(50/50wt%)mixture, however, was higher than for pure R-22 at side and bottom of the tube. Furthermore, a prediction for the evaporating heat transfer coefficient of the mixtures was developed based on the method of Yoshida et.al.'s. The resulting correlation yielded a good agreement with the data for the refrigerant mixtures.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.4
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• pp.53-61
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• 1994

An experimental study on heat pump cycle systematizing characteristics for non-azeotropic refrigerant mixtures of R-22+R-114 was reported. Data were obtained under steady state condition at the ranges of parameters, 550- 2, 170kcal/h, 670-2, 990kcal/h, 24-71kg/h, and 0-1, for as cooling capacity, heating capacity, mass 25, 50, 75, and 100 per cent of R-22 by weight fraction for R-22+R-114 mixtures. The results shown that the C.O.P of the 50wt% of R-22 mixture was considerably larger than for pure R-22 and other weight fraction of R-22 mixtures, but the compression power of the 25wt% of R-22 was lower than that of the pure R-22 and the other weight fraction of R-22 mixtures. The hightest value of cooling capacity was obtained at the conditions of evaporating temperature 5.deg.C and R-22 50wt% mixture. In general, with an increase in the R-22 weight fraction for fixed values of the other parameter, the cooling capacity increased at first, obtained a maximum, and then decreasd. This verified the importance of accurate weight fractions od refrigerant mixtures in the heat pump cycle.