• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.438-443
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• 2001

Plate impingement of the impulse wave discharged from the open end of a duct is numerically investigated using a CFD method. Harten-Yee Total Variation Diminishing method is used to solve the unsteady, compressible flow governing equations. The Mach number, the flat plate inclination and the distance between the duct exit and inclined flat plate are changed to investigate their effects on the impinging flow field. The impulse wave impingement on the inclined flat plate depends on Mach number $M_s$ and the plate inclination $\psi$. The pressure distributions on the inclined flat plate show that for a small r/D, the peak pressure at the center of an inclined flat plate decreases with an increase in the plate inclination $\psi$ in the range of $\psi$ from $45^{\circ}$ to $60^{\circ}$ but for a large r/D, the peak pressure decreases with an increase in $\psi$ in the range of $\psi$ from $75^{\circ}$ to $90^{\circ}$. It is also found that for all of r/D, the peak pressure at the center of an inclined flat plate has a maximum value in $\psi=90^{\circ}$.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1140-1149
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• 2004

The absorption characteristics of water vapor into a LiBr-H$_2$O solution flowing down on finned inclined surfaces are numerically investigated in order to study the absorbing performances of different surface shapes of finned tubes as an absorber element. A three-dimensional numerical model is developed. The momentum, energy, and diffusion equations are solved simultaneously using a finite difference method. In order to obtain the temperature and concentration distributions, the Runge-Kutta and the Successive over relaxation methods are used. The flat, circular, elliptic, and parabolic shapes of the tube surfaces are considered in order to find the optimal surface shapes for absorption. In addition, the effects of the fin intervals and Reynolds numbers are studied. The results show that the absorption mainly happens near the fin tip due to the temperature and concentration gradient, and the absorbing performance of the parabolic surface is better than those of the other surfaces.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.185.1-185
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• 2001

• 설비공학논문집
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• 제17권11호
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• pp.1014-1021
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• 2005

Flow channels with non-circular cross-sections are encountered in a wide variety of heat exchangers. Accurate friction factor and Colburn j factor data are essential for the design and viable applications of such heat exchangers. In this study, an analysis is con ducted on heat transfer and pressure drop characteristics for tube-bundle heat exchanger with various arrangements of tubes, of which their geometry could easily be modified from a circular one in a harsh environment. The parameters investigated are aspect ratio, pitch, and inclined angle of tubes. The results obtained are: (1) Aspect ratio has larger influence on the j and f factor than pitch; (2) As aspect ratio increases, both j and f factors decrease; (3) The high performance is achieved when the pitch and aspect ratio are in the range of 1.5${\~}$2.5 and 1.25${\~}$2.0, respectively; and (4) the inclined arrangements of tubes show unfavorable results for both heat transfer and pressure drop characteristics in spite of the positive possibility of condensate removals in a latent heat recovery system.

• 대한기계학회논문집B
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• 제38권1호
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• pp.9-16
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• 2014

본 논문은 경사진 원형관에서 표면장력과 중력으로 구동되는 비뉴턴 유체(멱법칙 모델)의 유동 및 변위를 이론적으로 연구한 것이다. 그리고 표면장력에 의하여 연속적으로 원형관 내로 유입되는 비뉴턴 유체의 변위를 기술하기 위한 지배방정식을 처음으로 개발하였다. 뉴턴의 운동방정식으로부터 유도된 식은 2계 비선형이며 비제차인 형태의 상미분 방정식이다. 지배방정식의 해를 수평관에서 변위를 시간의 함수로 기술한 식 및 실험과 비교한 결과 정량적으로 동일한 일치를 보였다. 여기에 더하여 정상상태인 힘의 균형식의 결과에 대해서도 정확한 일치로 나타남을 확인할 수 있었다.

• 대한기계학회논문집B
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• 제32권5호
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• pp.327-334
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• 2008

Effects of tube inclination on pool boiling heat transfer have been studied for the saturated water at atmospheric pressure. For the analysis, seven inclination angles varying from the horizontal to the vertical and two tube diameters(25.4 and 30.0 mm) are tested. According to the results, inclination angles result in much change on heat transfer. For the same wall superheat(about $5.3^{\circ}C$) the ratio between two heat fluxes for the $45^{\circ}$ inclined and the vertical has the value of more than five when the tube diameter is 25.4mm. As the inclination angle is increasing from the horizontal to the vertical direction heat transfer is gradually increasing because of the increase in liquid agitation. However the detailed tendency depends on the ratio between the tube length and the diameter.

• 한국안전학회지
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• 제19권2호
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• pp.11-15
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• 2004

The fretting-fatigue by leaking is one of the significant degradation in steam generator tubes. In this study, the burst pressure of inclined damaged steam generator tubes were obtained from three criterions by using the finite element method. The analysis results were also compared with the experiment data from published references and they showed a good agreement with the experiment data.

• 한국연소학회지
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• 제12권1호
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• pp.11-20
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• 2007

The supersonic combustion experiments are carried out using T3 free-piston shock tunnel. Different shock tube fill pressures have various inflow conditions. $15^{\circ}$ inclined hydrogen fuel injection is located before the cavity. Oblique shock is generated from the cavity and reflects off the top and bottom wall. For non-reacting flow, fuel makes the shear layer thicker above the cavity therefore, the shock is generated just before the trailing edge. This research has self-ignition in the combustor. For reacting flow, as the equivalence ratio increases, flame starts to generate near the injector or occur in the recirculation zone before the injector. High fuel injection sustains the jet shape in the cross flow and air can mix with fuel along the shear layer. Therefore, two flame layers find above the cavity for high equivalence ratio.

• 한국연소학회지
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• 제12권1호
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• pp.21-27
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• 2007

The supersonic combustion experiments are carried out using T3 free-piston shock tunnel. Different shock tube fill pressures have various inflow conditions. $15^{\circ}$ inclined hydrogen fuel injection is located before the cavity. Oblique shock is generated at the trailing edge of the cavity and reflects off the top and bottom wall. For non-reacting flow, static pressures in low equivalence ratio are similar to those in no fuel injection. As equivalence ratio is increased, static pressures are increased in the duct. In the similar equivalence ratio, static pressures are increased when total enthalpy is decreased. For reacting flow, the flame is occurred near the cavity. The combustion is weak locally in the middle of the duct. The up and down pressure distribution in the duct means that the supersonic combustion is generated.

• Journal of Advanced Marine Engineering and Technology
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• 제24권5호
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• pp.119-124
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• 2000

A finite element method is applied to investigate the characteristics of the fluid flow and heat transfer performance in a channel in terms of the various effects of baffle cuts, baffle angles, and leakages. The results show that the decrease of a baffle cut gives a good heat transfer enhancement. However, it also increases pressure drop. In the case of an inclined baffle, the result shows that the pressure drop decreases with a reasonable heat transfer performance. But a steeply inclined baffle gives adverse effects on the performance of the channel. The clearances between baffle-to-shell and tube-to-baffle affect the overall performance. The effects of these parameters are discussed in details.