• 대한기계학회논문집B
• /
• 제20권8호
• /
• pp.2626-2636
• /
• 1996

A study of soot deposition and reentrainment was carried out both theoretically and experimentally to understand behavior of soot formed by incomplete combustion in a diesel engine. Theoretically, soot deposition on engine cylinder wall and/or piston head was studied with a stagnation point flow approximation. Soot reentrainment occurred upon exhaust gas blowdown was also studied by assuming a long-normal shear velocity distribution. Experimentally, a LPG$O_2/N_2$ flame impinging on a disk, produced by a concentric tubular burner, was chosen as deposition configuration and a shear flow unit with compressed air was installed for the study of reentrainment. For selected flame configuration, soot deposition measurements were conducted and showed that the dominant deposition mechanism was thermophoresis. Distributions of gas temperature and soot number density were estimated by combining data obtained by a B-type thermocouple with a thermophoretic transport theory. Disk temperature distributions were directly measured using a K-type thermocouple. Soot size and morphology were estimated from a TEM photograph. Ratios of soot deposit to reentrained amount were measured for a wide range of shear flow velocities, which showed that the reentrainment model was reasonable.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집D
• /
• pp.489-496
• /
• 2001

Two perforated plates are used to investigate local heat/mass transfer characteristics in an impingement/effusion cooling system. A naphthalene sublimation method is conducted to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. The two plates are placed in parallel position with gap distances of 1, 2, 4 and 6 times of effusion hole diameter. The effects of hole arrangements of the plates are studied for staggered, square, and hexagonal arrays. The experiments are conducted at Reynolds number of 10,000 based on the effusion hole diameter. The results show that the smaller hole size in the staggered array has the higher transfer coefficients on the stagnation region due to the formation of higher momentum flows through the impingement holes. In the square array, heat/mass transfer on the target plate is more uniform as the number of impingement holes increases. High and uniform heat/mass transfer coefficients are obtained in the hexagonal array.

• 대한기계학회논문집B
• /
• 제22권6호
• /
• pp.771-787
• /
• 1998

A Navier-Stokes code with a modified low Reynolds number k-.epsilon. turbulence model was used to study the unsteady transitional boundary layer flow due to rotor-stator interaction. The modification, proposed by Launder, to improve prediction of stagnation flows was incorporated to the low Reynolds number k-.epsilon. turbulence model by Fan-Lakshminarayana-Barnett. Numerical solution is shown to capture well the calmed laminar flow as well as the wake induced transitional strip due to rotor-stator interaction and shows improvement, in terms of onset of transition and its length, over previous Euler/boundary layer solution. The turbulent kinetic energy shows local maximum along the upstream rotor wake in the wake induced transitional strip and this characteristics is observed untill the end of transition. The wake induced strip also shown apparent even in the laminar sublayer as the upstream rotor wake penetrates inside the boundary layer.

• 대한기계학회논문집
• /
• 제12권2호
• /
• pp.373-380
• /
• 1988

본 연구의 목적은 음장의 입자속도가 기류의 평균속도와 비슷한 크기인 경우에 원통으로부터 열전달의 동특성과 한 사이클의 평균값인 평균열전달이 음장에 의하여 어떠한 영향을 받는가를 구하기 위한 것이다.

• 환경위생공학
• /
• 제14권3호
• /
• pp.116-122
• /
• 1999

The purpose of this study is to develop new process named "hydrogen peroxide dissolution method". This process used hydrogen peroxide, which is harmless to human body and oxidize molybdenum wire selectively.The advantages of hydrogen peroxide dissolution method were no discharge of noxious matter when dissolution of molybdenum wire which used as the center supporter, reactions occur in room temperature and easy to recover dissolved molybdenum. This study was aimed at gathering the basic data of molybdenum wire dissolution-recovery process and proposes the reaction condition of molybdenum wire dissolution-recovery process and the factors influencing those reactions. The results were as follows:1. In the dissolution of molybdenum wire, the early condition of reaction was $15^{\circ}C$, and the temperature condition of state was $32^{\circ}C$. 2. 1) In the GSL-60W type, P.W.(Piece weight) was 11.89mg, C.R. was $65.6\Omega$. 2) In the FL-20W type, P.W. was 11.60mg, C.R. was $4.6\Omega$. 3. The molybdenum of process water was treated of a precipitation after dry and after stagnation in the one day, the molybdenum of upper water was treated of precipitation after dry and after congelation.

• 한국조리학회지
• /
• 제9권1호
• /
• pp.22-38
• /
• 2003

This study divided all cooking-related employees into hotel organization and family restaurant organization, and analyzed the present duties´ characteristics along with an analysis on population statistics. Also, the study examined each employee´s recognition degree of his/her duty in each group and investigated which knowledge and skill they thought as important parts for their developing ability and attaining duties in the future. The collected data tell the followings; with respect to the characteristics of the employees´ duties, the characteristics of hotel employees were different from those of family restaurant employees; in case of hotel employees, the characteristic items recognized at a high level were the importance of duty, independence, self-reliance, the knowledge degree, career, controlling-ship, and development-ship. On the contrary, in case of family restaurant employees, the highly recognized items were complexity of duty, stagnation-ship, and human relationship. Generally, it was clear that family restaurant employees showed more complaints than hotel employees did in the section of recognition degree on the present duties. The imperfect matter is that this study could not specify particulars or details of knowledge and skills that are necessary to make a perfect food-service company. However, this study will become a basis to develop further research on a perfect supposition and detailed particulars by detailed variables in a demonstrative way.

• 대한기계학회논문집
• /
• 제3권3호
• /
• pp.91-97
• /
• 1979

Boundary layer equations (partial differential equations) can be transformed to ordinary diffential equations with constant coeffieients in terms of similarity transformed to ordinary differential equations with constant coeffieients in terms of similarity transformations in the heat tranfer analysis on the surface of any axiaymmetric boiles. The azimuth functions can not be uniquely determined because of the singular behavior at the stagnation point(X=0.deg.).In spite of the azimuth functions behaving singularly, many of researchers have analyzed the heat transfer problem on a horizontal chlinder or a sphere, supposing the set of solutions( $H_{1}$ & G$_{1}$) of being yieled from the simple differential equation to be unique solution of therazimuth functions. In order to ascertain whether mathematical incompatibility as mentioned above can be admitted in the viewpoint of enginerring or not, condensation heat transfer coefficients on a sphere are computed for all azimuth functions( $H_{1}$ G$_{1}$ & $H_{2}$ G$_{2}$) and comparisons with the experimental result are discussed.

• 대한기계학회논문집B
• /
• 제23권8호
• /
• pp.997-1009
• /
• 1999

Silica particle formation and growth process including chemical reaction, coagulation and sintering was studied in a counterflow diffusion flame burner. The counterflow geometry provides a one dimensional flow field, along the stagnation point streamline, which greatly simplifies interpretation of the particle growth characteristics. $SiCl_4$ has been used as the source of silicon in hydrogen/oxygen/argon flames. The temperature profiles obtained by calculation showed a good agreement with experiment data. Using one and two dimensional sectional method, aerosol dynamics equation in a flame was solved, and these two results were compared. The two dimensional section method can consider sintering effect and growth of primary particle during synthesis, thus it showed evolution of morphology of non-spherical particles (aggregates) using surface fractal dimension. The effects of flame temperature and chemical loading on particle dynamics were studied. Geometric mean diameter based on surface area and total number concentration followed the trend of experiment results, especially, the change of diameters showed the sintering effect in high temperature environment.

• 에너지공학
• /
• 제8권2호
• /
• pp.203-212
• /
• 1999

한국은 선진국의 원자력 산업 침체와는 대조적으로 아직도 활발하게 원자력발전소를 건설 운영하고 있으며 앞으로도 이와 같은 원자력발전을 적극 고려한 전력에너지 정책기조를 유지하려고 하고 있다. 한국의 경제규모는 세계 10위권에 진입하려 하고 있으며 OECD에 가입하는 등 국가의 전반적인 위상이 향상되었으며 현재 국제 원자력 시장에서 한국은 매우 중요한 고객인 동시에 수혜적 입장에서 벗어난 잠재적인 공급자라는 점이 널리 알려져 있다. 그러나 한국의 원자력산업을 세계화하기 위한 기반은 아직 미약한 상태에 머물러 있다. 이는 한국이 원자력발전소를 도입하기 시작한 1970년대초 이래로 기술국산화란 산업적 측면을 강조하여 원자력정책을 다루어 오면서 국제정치 및 국제교역 측면을 중시하지 않았기 때문이다. 이러한 배경에서 본 논문은 한국이 국제 원자력 통상 분야에서 활동 영역을 넓히고 국제 원자력정책 결정 과정에 보다 많은 영향력을 행사하기 위한 전략을 제시하고 있다.

• 대한약침학회지
• /
• 제10권3호
• /
• pp.149-155
• /
• 2007

Objectives The purpose of this study is aimed at diagnosing and suggesting treatment plans for commonly seen clinical manifestation of heat symptom in the upper body and coldness in the lower body, also known as hot above, cold below syndrome. Methods Various reasons attribute to the presence of hot above, cold below syndrome, but mainly contributed by blockage of normal Qi flow by abnormality of heart-kidney root, spleen-stomach axis, and liver-lung axis. Diagnosing these abnormalities and timely alleviation to the healthy state is presented in the study. Results 1For heat in the upper body, Huang Lian Jie Du Tang(黃連解毒湯), CF, or JsD pharmacopuctures are injected on GB21, GB20. Qi stagnation in the thoracic area is treated with BUM injection on CV17. For impairment of transportation and transformation in the middle energizer, BUM pharmacopuncture is injected on CV12. Coldness in the lower energizer was relieved by bee venom or Sweet BV(Bee Venom free from enzymes) on CV6. Conclusion Above proposed methods of regulating water-fire were effective in treating hot above, cold below syndrome in clinical manifestations. But once the symptom subsides, treatment focused on eliminating innate cause should be rendered to achieve more successful results.