• Journal of Advanced Marine Engineering and Technology
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• 제39권6호
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• pp.609-613
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• 2015

축방향 거리에 따라 확대되는 정사각 채널에서 발달된 난류유동의 국부 난류 열전달과 압력강하를 실험적으로 조사하였다. 정사각 확대채널에 한 면에만 높이가 10 mm인 리브를 설치하였다. 리브의 충돌 각은 $30^{\circ}$, $45^{\circ}$, $60^{\circ}$ 그리고 $90^{\circ}$로 한 벽면에 만 설치하였다. 레이놀즈수가 22,000~79,000의 범위에서 실험을 수행하였다. 연구 결과 $45^{\circ}$의 리브 충돌각이 가장 우수한 열전달 성능을 보였다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(2)
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• pp.885-890
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• 1995

사용후핵연료 수송용기는 충돌사고에 대한 구조적 건전성을 입증하기 위하여 9 m 자유낙하조건에 대하여 수송용기의 충돌거동을 평가해야 한다. 본 연구의 목적은 수송용기가 9 m 높이에서 충돌면과 경사각을 갖고 충돌할 때의 동적거동을 파악하기 위한 것이다. 수송용기가 충돌과 함께 회전하며 연속충돌을 일으키는 45$^{\circ}$ 이하의 작은 경사각을 갖고 충돌할 매 수송용기에 발생하는 응력, 가속도, 충돌력 등을 분석하여 동적거동을 파악하였다. 또한, 수송용기의 경사각도를 변화시키며, 경사각도의 변화가 수송용기의 동적 거동에 미치는 영향을 파악하였다.

• 설비공학논문집
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• 제14권6호
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• pp.477-484
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• 2002

A numerical investigation of the performance of the plate heat exchanger with rectangular winglet is conducted to examine the combined effect of vortex generator and louver fins. Velocity and temperature fields and spanwise averaged Nu and friction factor are presented. Enhancement of heat transfer and flow loss penalty is evident. A Parametric study of three factors (Re, angle of attack and louver angle) with levels of 5 (Re= 300, 500, 700, 900, 1100), 4($\alpha=15^{\circ}, 30^{\circ}, 45^{\circ}, 90^{\circ},$), and 4($\beta=0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}$), respectively, indicates the performance defined by the ratio of heat transfer enhancement to flow loss penalty shows monotonic behavior for each parameter alone but the interactions between parameters is found to be considerable effect on the performance of heat exchanger and should be considered in design. The effect of stamping is also examined.

• Journal of Advanced Marine Engineering and Technology
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• 제30권2호
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• pp.275-283
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• 2006

Experiment and three dimensional numerical investigations of incompressible turbulent flow through square channels with one- and two-sided ribbed walls are performed to determine pressure drop and heat transfer. The CFX(version 5.7) software package is used for the computation. The ribbed walls have a $45^{\circ}$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The numerical results coincide with experimental data that obtained for $7,600{\le}Re{\le}24.900$, the pitch-to-rib height ratio (p/e) of 8.0. and the rib height-to-channel hydraulic diameter ratio ($e/D_h$) of 0.0667. The results show that values of local heat transfer coefficient and friction factor in the channel with two-sided ribbed wall are higher than those in the channel with one-sided ribbed walls.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.1083-1090
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• 2005

Repeated ribs are used on heat exchange surfaces to promote turbulence and enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concern detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue is tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall have a 45$^{\circ}$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increase with increasing the number of rough walls.

• 동력기계공학회지
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• 제9권1호
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• pp.30-35
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• 2005

Repeated ribs are used on heat exchanger surfaces to promote turbulence and to enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concerns detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue was tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall had a $45^{\circ}$ inclined square rib. Uniform heat flux was maintained on the whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increased with increasing the number of rough walls.

• Journal of Advanced Marine Engineering and Technology
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• 제40권4호
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• pp.270-274
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• 2016

양 벽면이 수축되는 채널에서 ${\vee}/{\wedge}$형 리브의 각도가 열전달에 미치는 효과를 실험적으로 조사하였다. 한 벽면에만 설치된 ${\vee}/{\wedge}$형 리브의 충돌 각은 각각 $30^{\circ}$, $45^{\circ}$, $60^{\circ}$ 그리고 $90^{\circ}$이다. 리브의 높이(e)는 10 mm 그리고 리브 간격(p)과 높이(e)비는 10으로 제작하였다. 길이가 1,000 mm인 시험 부는 입구의 단면적은 $100mm{\times}100mm$, 출구는 $50mm{\times}100mm$으로 제작하였다. 레이놀즈수가 22,000에서 75,000까지의 범위에서 실험을 수행하였다. 연구결과 전체적으로 레이놀즈 수가 높을수록 누셀트 수가 컸고, ${\wedge}$형 $45^{\circ}$ 리브가 가장 누셀트 수가 컸다.

• 한국분무공학회지
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• 제10권1호
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• pp.17-23
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• 2005

Even though a relatively complete knowledge base has been established for diesel sprays, much of the knowledge cannot be directly translated to correlate the characteristics of gasoline spray. The macroscopic characteristics of gasoline impingement spray was investigated with photographic and image processing technique by Particle Motion Analysis System. The injector with single hole nozzle diameter of 0.28 mm was used in this experiment and the injection duration was selected as 10 msec. The injection pressure with 0.3, 0.35, and 0.4 MPa, impingement distance or 70, 100 and 130m, impingement angle or 0.15, 30 and $45^{\circ}$ were employed for the variables to affect the spray characteristics of impinging spray. It is clear that there is the analogy on the spray tip penetration between the gasoline impinging jet and diesel free jet. The spray tip penetration of impinging gasoline spray is proportional to the quarter power of the time after start of injection. The maximum height of impinging gasoline spray is also proportional to the quarter power of the time regardless of impingement distance, impingement angle and injection pressure. In addition, the effect of impingement angle on the spray tip penetration is significant according to the time after start of injection, even though there is minor effect in the initial stage of time after start of injection. Moreover, there is no remarkable effect of injection pressure on the spray tip Penetration under the experimental condition used in this study.

• 대한기계학회논문집B
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• 제23권5호
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• pp.678-686
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• 1999

The purpose of this work is to Investigate the pressure drop and the heat transfer characteristics in the channel of plate heat exchanger with crossed-discrete ribs. The flow is assumed to be three-dimensional, laminar and periodically fully developed. Computations have been carried out for angles of attack from $0^{\circ}$ to $90^{\circ}$ and ratios of rib height from 0.15 to 0.46 for various values of Reynolds and Prandtl numbers. The heat transfer was improved by inclined ribs generating helical vortices and secondary flows. The results show that the pressure drop has a maximum value at $70^{\circ}$ and the heat transfer has a maximum value at $45^{\circ}$. As the rib height increases, the pressure drop and the heat transfer increase quadratically, and the increasing rate of pressure drop is higher than that of the heat transfer. As Reynolds number increases, the pressure drop increases in proportion to the square of Reynolds number and the heat transfer increases linearly.