• 설비공학논문집
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• 제8권1호
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• pp.140-150
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• 1996

CFC-12, which has been used most widely in automobile air conditioners and household refrigerators is scheduled to be phased out soon because of its high ozone depletion potential. Now HFC-134a is suggested as an alternative refrigerant for CFC-12. In this Study, we intended to investigate how PAG oil influence evaporation heat transfer and flow pattern, using R-134a and PAG oil influences evaporation heat transfer and flow pattern, using R-134a and PAG oil in the horizontal miro-fin evaporation tube. Experiments were conducted under the flowing est conditions : mass velocity 86-250kg/$m^2$s, heat flux 5-30 ㎾/$m^2$, oil concentration 0-21 wt.% and saturation temperature 5$^{\circ}C$. Local evaporation heat transfer coefficients were found to be higher at the top, side and bottom of the tube in this order. Average heat transfer coefficients turned out to increase with oil concentration increment up to 3 wt.% oil concentration, whereas heat transfer coefficients gradually decreased over 3 wt.% oil concentration, because of oil-rich liquid film was formed on the heat transfer surface. Flow patterns were rapidly transitioned to annular regimes up to 3 wt.% oil concentration. In case of pure refrigerant, measured heat transfer coefficients in the experiments were similar to those of Kandlikar＇s correlation.

• 설비공학논문집
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• 제15권10호
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• pp.852-859
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• 2003

R407C is considered as an alternative refrigerant of R22 for air conditioners. An experiment was carried out to investigate the characteristics of the evaporation heat transfer and pressure drop for refrigerant R407C flowing in a fin-and-tube heat exchanger used for commercial air-conditioning unit. The experimental data were useful in analyze the effects of the temperature glide and superheat for R407C. Test were conducted at the conditions of inlet refrigerant evaporation temperature of 7$^{\circ}C$, inlet air relative humidity of 50%, and refrigerant mass fluxes varying from 150 to 250 kg/m$^2$s. Representative results show that the heat exchanger performance for R407C evaporation is significantly affected by the change of the flow pattern from two-phase to super-heated vapor flow.

• 콘크리트학회논문집
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• 제17권4호
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• pp.655-662
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• 2005

Evaporation of concrete influences the development of both initial transverse cracking and delamination in the concrete slab. It was suggested that spatting distress might develop in the slab where the initial transverse cracking occurred by theoretical equations and a field investigation. Thus, efforts to prevent the evaporation of concrete using proper curing methods are required to minimize the distresses of the slabs. Effective curing thickness (ECT) concept was used in this paper to evaluate various curing methods used to prevent the evaporation from concrete. Curing effectiveness quantified by the ECT of different types and amounts of curing compound under various curing conditions was investigated based on the results of laboratory tests. According to the test results, the wind speed is inferred to be a significant factor of the magnitude and continuance duration of the curing effectiveness.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.217-222
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• 2000

An understanding of the behaviour of soft clay soils is important in a large number of civil engineering applications, including dredging operations, land reclamation and slurry management such as disposal and storage. Although the details of the behaviour depend on parameters such as the soil mineralogy, the pore water chemistry, the organic content and the microbiology, there are general features that are typical in many cases. The purpose of this paper is to present and discuss some of evaporation and desiccation observed in laboratory experiments under controlled conditions. Desiccation of dredged material is basically removal of water by evaporation which is controlled by weather and material type, etc. This study shows that (1) solar radiation, (2) wind velocity, (3) material depth, (4) trench depth are important factors in desiccation of dredged ultra soft clay.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.289-290
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• 2012

In this study, it was evaluated about shrinkage properties of high strength concrete according to poly mix fiber and moisture evaporation condition. As a results, When concrete was mixed with poly mix fiber of spalling control, it reduced effect of shrinkage independent of the evaporation conditions of unsealed and sealed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 추계 학술논문 발표대회
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• pp.75-76
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• 2012

In this study, it was evaluated about creep properties of high strength concrete according to compressive strength and moisture evaporation condition. As a results, creep strain and creep coefficient was greatly affected by moisture evaporation conditions rather than compressive strength. Also, the effect of fiber mixed was not show big difference.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.591-596
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• 2001

The purpose of this paper Is to present and discuss some of evaporation and desiccation observed in laboratory experiments under controlled conditions, and is to improve PTM(Progressive Trenching Method) operating technique. PTM is the technically feasible and economically justifiable dewatering and desiccation technique for dredged material containment areas. A series of laboratory experiments with large model test were carried out to get evaporation rate and strength increase. Surface desiccation of dredged material is basically changed by evaporation characteristics which is controlled by weather and trench type, etc. This study shows that trench depth and rain fall are important factors in desiccation of dredged soft clay.

• Nuclear Engineering and Technology
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• 제28권6호
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• pp.532-541
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• 1996

Theoretical and numerical study on heat transfer and evaporation in the vertical channel has been carried out and basic correlations have been derived for the heat transfer evaluation of PCCS. Analysis program was developed with low-Reynolds-number k-$\varepsilon$ model and surface transfer rates were calculated for the turbulent natural convection in the vertical channel. In relation to dry cooling by buoyancy-driven air, first, the system parameters which govern overall heat transfer rate are determined through the adequate nondimensionalization procedure. After comparison with existing experimental data, numerical results are used to derive heat transfer correlation by sensitivity calculations. In relation to wet cooling by falling water film, numerical analysis are carried out for evaporation process with real film surface conditions and evaporation correlation is derived through analogy concept and correction factors.

• 약학회지
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• 제44권6호
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• pp.511-520
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• 2000

Various bupivacaine-loaded microspheres were prepared from poly (d,l-lactide) (PLA) or poly (d,l-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. PLA and PLGA microspheres were prepared by w/o/w and w/o/o multiple emulsion solvent evaporation, respectively. The effects of process conditions such as emulsification speed, emulsifier type, emulsifier concentration and internal/external phase ratio on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency was higher in the microspheres prepared by w/o/o multiple emulsion than that by w/o/w multiple emulsion method, because the solubility of bupivacaine HCI was decreased in oil phase compared with water phase. The prepared microspheres had an average diameter between 1 and $2\;{\mu}M$ in all conditions of two methods. In morphology studies the PLA microspheres showed an irregular shape and smooth surface, but PLGA microspheres had a spherical shape and smooth surface. The release pattern of the drug from microspheres was evaluated on the basis of the burst effect and the extent of the release after 24h. The in vitro release of bupivacaine HCl from microspheres showed a large initial burst release and $60{\sim}80%$ release within one day in all conditions of two methods. The extents of the burst release against PLA and PLGA microspheres were $30{\sim}50%$ and $50{\sim}80%$ within 20min, respectively. This burst release seems to be due to the smaller size of microspheres and the solubility of drug in water.

• 한국재료학회지
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• 제21권1호
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• pp.56-66
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• 2011

Multi-source evaporation is one of the methods to improve the thickness uniformity of thin films deposited by evaporation. In this study, a simulator for the relative thickness profile of a thin film deposited by a multi-source evaporation system was developed. Using this simulator, the relative thickness profiles of the evaporated thin films were simulated under various conditions, such as the number and arrangements of sources and source-to-substrate distance. The optimum conditions, in which the thickness uniformity is minimized, and the corresponding efficiency, were obtained. The substrate was a 5th generation substrate (dimensions of 1300 mm ${\times}$ 1100 mm). The number of sources and source-to-substrate distance were varied from 1 to 6 and 0 to the length of the major axis of the substrate (1300 mm), respectively. When the source plane, the area on which sources can be located, is limited to the substrate dimension, the minimum thickness uniformity, obtained when the number of sources is 6, was 3.3%; the corresponding efficiency was 16.6%. When the dimension of the source plane is enlarged two times, the thickness uniformity is remarkably improved while the efficiency is decreased. The minimum thickness uniformity, obtained when the number of sources is 6, was 0.5%; the corresponding efficiency was decreased to 9.1%. The expansion of the source plane brings about not only the improvement of the thickness uniformity, but also a decrement of the efficiency and an enlargement of equipment.