• The Korean Journal of Rheology
• /
• v.3 no.2
• /
• pp.117-123
• /
• 1991

현탁액에 대한 기본적인 유변학적 특성을 조사하기 위해 입자의 부피분율에 따른 점도의 변화를 측정하였고 현탁액의 Die Swell 현상에 대해 실험적으로 규명하였다. 뉴톤성 특성을 조사하기 위해 입자의 부피 분율에 따른 점도의 변화를 측정하였고 현탁액의 Die Swell 현상에 대해 실험적으로 규명하였다. 뉴톤성 특성을 갖는 Silicone 오일을 현탁 매질 로 사용하였고 미세한 유리 구슬이 filler로써 사용되었다. 현탁액의 점도는 Couette 점도계 와 모세관 점도계를 사용하였다. 관의 입구와 출구에 대한 보정을 위해서 Bagley의 방법을 이용하였으며 중력으로 인한 Swell의 감소효과를 제거하기 위해서 분사 유체와 유사한 밀 도를 지니며 분사 유체와 섞이지 않는 유체를 담은 부력용기가 사용되었다. Die Swell 현상 은 사진을 찍고 이를 정밀한 확대경을 통해 관찰함으로써 수치적으로 값을 얻었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.4
• /
• pp.348-353
• /
• 2011

Characteristics of cryogenic single jet flow were investigated. Liquid nitrogen was injected into a high-pressure chamber and formed single jet. Ambient condition around jet was changed from subcritical to superctirical condition of nitrogen. Injector geometries also were changed. A shape of the jet and core diameter were measured by flow visualization technique, and core spreading angle was calculated. Flow instability was found at atmospheric pressure condition. As ambient pressure increased, core spreading angle was increased and maintained after certain pressure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.5
• /
• pp.397-405
• /
• 2003

Heat and fluid flow in a compressor into which liquid refrigerant is injected for the purpose of reducing discharge gas temperature in a heat pump system has been numerically studied. A mechanistic approach encompassing liquid jet breakup and droplet evaporation has been performed to investigate the effects of liquid injection on the spacial and temporal variation of the gas temperature and pressure inside the compressor cylinder. Various parameters, such as liquid injection mass, time, duration and droplet size, are considered in the present study to elucidate the flow field inside the compressor. As the injection mass is increased, discharge gas temperature is decreased, while the pressure is increased due to the added mass of the injection. For the injected liquid mass corresponding to 15% of the total vapor mass in the cylinder, the discharge gas temperature drops by 22.4 K. It is observed that the droplet size plays a major role in the evaporation rate of the droplets that determines the degree of the discharge temperature drop.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.3
• /
• pp.244-250
• /
• 2000

An air source heat pump using liquid injection technique, which can be applied for very low temperature climate, has been simulated to examine the design options. Comparison between the simulation and experiment has been carried out to validate the simulation method. Effects of various design parameters such as liquid injection rate and injection pressure are Investigated to optimize the performance of the heat pump. Finally, optimal liquid infection rate and injection pressure to maintain sufficient heating capacity and moderate discharge refrigerant temperature are suggested when the heat pump was operated at very low outdoor temperature.

• Applied Chemistry for Engineering
• /
• v.5 no.5
• /
• pp.836-842
• /
• 1994

The optimum design conditions of gas sparger pipe and the effects of operating variables on $SO_2$ removal efficiency have been examined in Jet Bubbling Reactor. Geometry of gas sparser pipe of Jet Bubbling Reactor is a very important factor to obtain a effective gas-liquid contact. Test results revealed that Reynolds numbers at sparger and slot have to be kept greater than 12,000 identically at a given gas velocity. $SO_2$ removal efficiency was a function of ${\Delta}P$, pH, inlet $SO_2$ concentration and particle size of limestone and was more sensitive to the change of ${\Delta}P$ than to the changes of others. The ${\Delta}P$ of at least 230mmAq must be maintained to acheive the above 90% $SO_2$ removal at pH of 4.0 which is considered as adequate operating pH. Higher $SO_2$ removal efficiency was obtained even at lower pH ranges, which resulted from the complete oxidation of the absorbed $SO_2$ to sulfates by adding air and consequently from the reduction of $SO_2$ equillibrium partial pressure in the gas-liquid interface The 99.5% of the limestone utilization was attained in pH range from 3.0 to 5.0 with regardless to the particle size of limestone employed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.3
• /
• pp.1040-1044
• /
• 2013

The present paper has been accomplished to elucidate the characteristics of temperature change in a car washer heater system for removal of frost formed at the surface of a car. The previous studies had used a simplified mathematical modeling to analyse the temperature change characteristics for a car washer heater system. In the present study, an unsteady computational fluid flow and heat transfer analysis for a washer heater system has been done by using computational fluid dynamic analysis method. From the present CFD analysis, the time dependent temperature change in a car washer heater system has been analysed and derived the heating time and ejection temperature of the washer liquid to establish the optimal design basis for a washer heater system.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.4
• /
• pp.509-520
• /
• 1996

Ultrafine calcim carbonate powders with the size of $0.05~0.1\;{\mu}m$ and the calcite phase were synthesized by the nozzle spouting method, which could be only obtained when high calcium ion concentration within slurry was maintained at the beginning of the reaction. But, in the regions of low ${Ca(OH)}_2$ concentration (0.5~1.0 wt%) or high ${Ca(OH)}_2$ concentration (<3.0 wt%), synthesized calcium carbonate powder was shown the large particle size with agglomeration. To obtain ultrafine calcium carbonate powder in this region, the methods of slurry circuation and $CO_{2}$ gas supply were changed during reaction. Resultly, it was possible to synthesize ultrafine particles (${\approx}0.05{\mu}\textrm{m}$)in the regions of low ${Ca(OH)}_2$ concentration (${\approx}0.5wt%$) and high ${Ca(OH)}_2$ concentration (${\approx}0.5wt%$), which can not be obtained the fine calcium carbonate powder still now.

• Clinical and Experimental Pediatrics
• /
• v.51 no.5
• /
• pp.481-486
• /
• 2008

Purpose : The aims of this study were to test the efficacy of vapocoolant spray to decrease the symptoms associated with pain in newborns undergoing heel stick and intramuscular injection and compare the pain relief effect of oral glucose. Methods : Randomized, controlled study including sixty newborns undergoing heel stick and intramuscular injection. Group 1 was heelsticked, Group 2 was intramuscular injected, Group A did not recieve any treatment, Group B recieved 30% glucose solution orally, Group C was applied vapocoolant spray symptoms and signs associated with pain at heel stick and intramuscular injection were measured with the premature Infant Pain Profile (PIPP) scale. Results : There was no significant difference in the PIPP score between intramuscular injected group control and heel stick group control (P=0.07). The mean PIPP score of Group 1A (control) $10.6{\pm}2.4$, Group 1B $5.5{\pm}2.0$, Group 1C $5.2{\pm}1.8$. The mean PIPP score 1B and 1C were significantly lower than control (1B P<0.001, 1C P<0.001). The mean PIPP score of Group 2A (control) $12.5{\pm}1.4$, Group 2B $7.0{\pm}1.7$, Group 2C $6.4{\pm}1.6$. The mean PIPP score 2B and 2C were significantly lower than control (2B P<0.001, 2C P<0.001). Conclusion : The antinociceptive effect of vapocoolant sparay is as effective as 30% oral glucose solution for pain control. So this study support the use of vapocoolant spray for reducing pain during painful procedure in the neonatal intensive care units.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.04a
• /
• pp.246-251
• /
• 2000

In this paper, Wire electric discharge grinding(WEDG) method for manufacturing the micro shaft was introduced and the machining characteristics was investigated. from the experimental results, it was concluded that high surface integrity could be obtained by use of dielectric fluid spraying method and small capacitive condenser.

• Food Science and Preservation
• /
• v.7 no.3
• /
• pp.337-341
• /
• 2000

Antimicrobial activities of oak smoke flavoring against saprogenous and food poisoning microbes were studied. When tested on a paper disc, antimicrobial activities were observed in all microbial species at a dose of as low as 20 ${\mu}{\ell}$, and microbial growth was completely suppressed with 70 ${\mu}{\ell}/5$ $m{\ell}$ during 3 days of incubation at $30^{\circ}C$ with 8 times diluted oak smoke flavoring. When 50 $m{\ell}s$ of distilled water and distilled water containing 500 ${\mu}{\ell}$ of oak smoke flavoring, which were added with small amount of dilute E. coli, were incubated for 10 days at $20^{\circ}C$, $3{\times}10^3$ CFU/$m{\ell}$ of E. coli and $1.9{\times}10^4$ CFU/$m{\ell}$ of total bacteria was counted in distilled water containing oak smoke flavoring.