• 대한기계학회논문집B
• /
• 제31권1호
• /
• pp.40-50
• /
• 2007

The present contribution describes the application of elliptic-blending second moment closure to predict the gas cooling process of turbulent super-critical carbon dioxide flow in a square cross-sectioned duct. The gas cooling process under super-critical state experiences a drastic change in thermodynamic and transport properties. Redistributive terms in the Reynolds stress and turbulent heat flux equations are modeled by an elliptic-blending second moment closure in order to represent strongly non-homogeneous effects produced by the presence of walls. The main feature of Durbin's elliptic relaxation second moment closure that accounts for the nonlocal character of pressure-velocity gradient correlation and the near-wall inhomogeneity guaranteed by the elliptic blending second moment closure.

• 한국응용과학기술학회지
• /
• 제20권1호
• /
• pp.51-56
• /
• 2003

Garlic extract using super-critical carbon dioxide is influenced by temperature and pressure, and the optimum condition can make under super-critical state. We can know the defects in process of super-critical extration, It can indicate the drop of product rate, energy loss and equipment expense etcs. The minimum inhibition concentration of microbe which garlic extract contains has apperared the concentration more than 800ppm in this experiment. According to the result of this experiment, we can know that the antibiosis effect in the microbe of staphylococcus and fungus has disappeared in the incubation time more than 12 hours.

• 한국응용과학기술학회지
• /
• 제20권4호
• /
• pp.309-315
• /
• 2003

Extraction of Natural Artemisia by using super critical carbon dioxide is operated under $40-50^{\circ}C$ and 200-250 atm, thus, conversion rate is very low as 7wt% while high energy is being wasted. When Natural Artemisia Extract is applied in the control of microbe, concentration and reaction time greatly affected to the growth of microbe. Especially, when refined oil concentration from Natural Artemisia added more than 1,000ppm, staphylococcus aureus and fungi are terminated completely. Thus, it is proven that Natural Artemisia Extract has antimicrobial effect.

• 한국응용과학기술학회지
• /
• 제21권3호
• /
• pp.204-213
• /
• 2004

Extraction of Sedum sarmentosum Bunge by super critical carbon dioxide was operated under $40-50^{\circ}C$and 200-250 atm, thus, yield of extraction was very low as 4 wt%. Rats were administrated with the extract orally once a day for succesive 6 days, followed by treatment with carbon tetrachloride ($CCl_4$) on the sixth day. The activities of aminotransferase, alkaline phosphatase, ${\gamma}$-glutamyl transpeptidase, lactate dehydrogenase and contents of triglyceride, total cholesterol in the extract-pretreated rats were decreased compared to the $CCl_4$controled rats, whereas content of HDL-cholesterol was increased. Especially content of hepatic malondialdehyde (MDA) and atherogenic index (AI) were decreased and HTR was increased in the extract-pretreated rats, and reduced peroxidative liver damage in the $CCl_4$-induced hepatotoxicity rats. In addition, activities of hepatic superoxide dismutase, catalase, glutathione peroxidase in the extract-pretreated rats were significantly decreased compared to the $CCl_4$ controled rats, but the content of glutathione was significantly increased. These results suggest that extract of Sedum sarmentosum Bunge has hepatoprotective effect in the $CCl_4$-intoxicated rats.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제12권4호
• /
• pp.176-183
• /
• 2004

Systematic methods to calculate thermodynamic properties of carbon dioxide, HFC-134a and HCFC-22 are presented. First, application of a basic method to identify the saturation state with given temperature or pressure is attempted and the feasibility of auxil­iary equations is tested. Next, detailed procedures are suggested to tell a phase when tem­perature/pressure and another property are specified. Finally the Newton-Raphson method is applied to calculate unknown thermodynamic properties fixing the state with the two inde­pendent properties specified. The procedures described here are utilized to develop a computer program, which is used to find the relation between temperature and pressure with maximum isobaric heat capacity for super-critical carbon dioxide.

• 설비공학논문집
• /
• 제15권5호
• /
• pp.389-396
• /
• 2003

Systematic methods to calculate thermodynamic properties of carbon dioxide, HFC-l34a and HCFC-22 are presented. First, application of a basic method to identify the saturation state with given temperature or pressure is attempted and the feasibility of auxiliary equations is tested. Next, detailed procedures are suggested to tell a phase when temperature/pressure and another property are specified. Finally Newton-Raphson method is applied to calculate unknown thermodynamic properties fixing the state with the two independent properties specified. The procedures described here are utilized to develop a computer program, which is used to find the relation between temperature and pressure with maximum isobaric heat capacity for super-critical carbon dioxide.

• Bulletin of the Korean Chemical Society
• /
• 제31권11호
• /
• pp.3221-3224
• /
• 2010

This study investigates the requirements of lithium-air cathodes, which directly influence discharge capacity. The cathodes of Li-air cell are made by using five different carbon materials, such as Ketjen black EC600JD, Super P, Ketjen black EC300JD, Denka black, and Ensaco 250G. The Ketjen black EC600JD provides discharge capacity of 2600 mAh/g per carbon weight, while that of Ensaco 250G shows only 579 mAh/g. To figure out the differences of discharge capacity from carbon materials, their surface area and pore volume are analyzed. These are found out to be the critical factors in determining discharge capacity. Furthermore, carbon loading on Ni foam and amounts of electrolyte are significant factors that affect discharge capacity. In order to investigate catalyst effect, electrolytic manganese dioxide (EMD) is incorporated and delivered 4307 mAh/g per carbon weight. This infers that EMD facilitates to break $O_2$ interactions and leads to enhance discharge capacity.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1394-1397
• /
• 2003

The first thing in developing injection molding and extrusion with microcellular foaming process is to get a grip on one phase state's rheology of gas and polymer solution. Understanding rheology is essential to design mold or die. and it is so important to control the condition of process. Also, this data is got the utmost out of simulation carrying out. In this paper, we will see the measurement of rheology in one phase that mixed polypropylene which contains talc with carbon dioxide of super critical fluid state, and will compare its result with the simulation result.

• 대한기계학회논문집B
• /
• 제39권10호
• /
• pp.779-786
• /
• 2015

이 연구의 목적은 열수력 성능을 향상시키기 위하여 PCHE의 새로운 유로 형상을 제안하는 것이다. 기존의 Zigzag 유로는 굽힘점에서 유동 박리와 역류 영역의 발생으로 높은 압력손실을 가지고 있다. 이 단점을 개선하기 위하여 굽힘점에 직관영역을 삽입하였다. 또한 직관의 길이 변화가 열전달 및 압력손실에 미치는 영향을 분석하였다. 새로운 형상과 기존 Zigzag 유로의 열수력 성능을 Goodness Factor를 사용하여 정량적으로 비교하였다. 질량유량은 $1.41{\times}10^{-4}$에서 $2.48{\times}10^{-4}kg/s$까지 변화 하였다. 1mm 직관길이에서 평균 Goodness Factor는 Zigzag보다 약 25% 정도 증가되었다.

• Korean Chemical Engineering Research
• /
• 제47권4호
• /
• pp.453-458
• /
• 2009

최근 환경문제가 크게 대두됨에 따라 고분자 합성과 가공 공정에서도 유기용매를 사용하지 않는 새로운 친환경적 공정의 개발이 요구되고 있다. 초임계 이산화탄소는 고분자 합성에서 용매로 사용될 경우, 기존의 유기용매와 비교하여 불연성이고 독성이 없으며 생성물과의 분리가 용이하다는 장점을 가지고 있다. 본 연구에서는 초임계 이산화탄소를 이용하여 의약학 및 화장품 분야에서 지능형 약물전달체로 사용할 수 있는 pH 감응형 하이드로젤인 P(MAA-co-EGMA) 하이드로젤을 수 백 nm 수준의 입자 형태로 합성하는 방법을 개발하였다. 그리고 중합과정에서 사용하는 분산안정제인 PtBuMA-PEO와 중합개시제인 AIBN이 하이드로젤 입자의 합성에 미치는 영향을 살펴보았다. 입자의 합성에서 PtBuMA-PEO의 함량이 증가할수록 입자 크기는 감소하였으나 AIBN의 함량에 따른 입자 크기의 변화는 관찰할 수 없었다. 합성된 P(MAA-co-EGMA) 하이드로젤 입자의 pH에 따른 팽윤 실험결과, PMAA의 $pK_a$인 pH 5를 전후하여 급격한 하이드로젤의 평형 질량팽윤비의 변화를 관찰할 수 있었다. 즉, pH 5보다 낮은 pH에서는 낮은 팽윤비를, 반면에 pH 5보다 높은 pH에서는 매우 높은 팽윤비를 나타내었다. 그리고 Rh-B를 이용한 방출실험에서는 높은 pH에서는 다량의 Rh-B가 하이드로젤 입자로부터 방출되었으나 낮은 pH에서는 Rh-B가 거의 방출되지 않는 pH에 따른 선택적 방출 특성을 나타내었다.