• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2003년도 하계학술대회 논문집
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• pp.227-227
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• 2003

• 한국추진공학회지
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• 제6권1호
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• pp.47-54
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• 2002

본 연구에서는 대기압하에서의 탄화수소계 연료인 제트유 연료액적에 대한 연소시 나타나는 액적의 연소특성 및 1차원 액적배열구조를 갖는 액적연소시 액적간격이 연소율 상수에 미치는 영향을 실험적으로 고찰하였다. 실험결과, 탄화수소계 연료인 제트유(jet A-1)는 실험조건하에서 단일 연료액적의 연소에 대해 액적크기에 상관없이 일정한 연소율 상수 $\kappa_c= 0.915{mm}^2$ 를 유지하였으며 대기압하에서 액적직경의 제곱$(d^2)$은 시간에 대하여 선형함수를 얻을 수 있었다. 또한, 1차원 배열구조를 갖는 액적연소(액적간격 $l/d_o$가 1.208~2.922)사이에 있어서 액적간격이 감소 할수록 액적의 연소율 상수 ${\kappa}_c$는 감소하였으며, 일정 액적간격을 가지는 액적군 연소시 3번째 액적 보다 2번째 액적의 연소율상수 ${\kappa}_c$에 미치는 영향이 더 크게 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.260-267
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• 2001

The objective of this study was to investigate the characteristics of jet flow and heat transfer caused by trapezoid rods array in impinging jet system. In this study, trapezoid rods have been set up in front of flat plate to serve as a turbulence promoter. The bottom width of trapezoid rod was W=4, 8mm and oblique angle were $80^{\circ}$. The space from rods to the heating surface was C=1, 2, 4mm, the pitch between each rods was P=30, 40, 50mm, and the distance from nozzle exit to flat plate was H=100, 500mm. This results were compared with the case without trapezoid rods. As a result, when rods are installed in front of the impinging plate, the acceleration of the jet flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Among test conditions, the heat transfer performance was best for the condition of W=8mm, C=1mm, P=30mm and H/B=10. The maximum heat transfer rate is about 1.9 times larger than that without trapezoid rods.

• 대한기계학회논문집B
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• 제24권3호
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• pp.435-442
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• 2000

The present study is conducted to investigate the local heat/mass transfer characteristics for flow through perforated plates. A naphthalene sublimation method is employed to determine the local heat/mass transfer coefficients on the effusion plate. Two parallel perforated plates are arranged for the two different ways: staggered and shifted in one direction. The experiments are conducted for hole pitch-to-diameter ratios of 6.0, for gap distance between the perforated plates of 0.33 to 10 hole diameters, and for Reynolds numbers of 5,000 to 12,000. The result shows that the high transfer region is formed at stagnation region and at the mid-line of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion hole. For flows through the perforated plates, the mass transfer rates on the surface of the effusion plate are about six to ten times higher than for effusion cooling alone (single perforated plate). More uniform and higher heat/mass transfer characteristic is obtained in overall region with small gap between two perforated plates.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1606-1615
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• 2001

The present study has been conducted to investigate heat/mass transfer characteristics on a target plate fur arrays of circular impingement jets with and without effusion holes. A naphthalene sublimation method is employed to determine local heat/mass transfer coefficients on the target plate. The effusion holes are located at the center of four injection holes in the injection plate where the spent air is discharged through the effusion hole after impingement on the target plate. For the array jet impingement without effusion holes, the array jets are injected into the crossflow formed by upstream spent air because the impinged jets must flow to the open exit. For small gap distances, heat/mass transfer coefficients without effusion holes are very non-uniform due to crossflow effects and re-entrainments of spent air. However, uniform distributions and enhanced values of heat/mass transfer coefficients are obtained by installing the effusion holes. For large gap distances, the crossflow has little influence on heat/mass transfer characteristics on the target palate due to the large cross-sectional open area between the injection and target plates. Therefore, the distributions and levels of heat/mass transfer coefficients are almost the same for both cases.

• 설비공학논문집
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• 제13권9호
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• pp.904-913
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• 2001

The objective of this study was to investigate the characteristics of jet flow and heat transfer caused by trapezoid rods array in impinging jet system. In this study, trapezoid rods have been set up in front of flat plate to serve as a turbulence promoter. The bottom width of trapezoid rod was W=4, 8 mm and oblique angle were 80$^{\circ}$. The space from rods to the heating surface was C=1, 2, 4 mm, the pitch between each rods was P=30, 40, 50 mm, and the distance from nozzle exit to flat plate was H=100, 500 mm. This results were compared with the case without trapezoid rods. As a result, when rods are installed in front of the impinging plate, the acceleration of the jet flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Among test conditions, the heat transfer performance was best for the condition of W=8 mm, C=1 mm, P=30 mm and H/B=10. The maximum heat transfer rate is about 1.9 times larger than that without trapezoid rods.

• 에너지공학
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• 제21권2호
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• pp.187-193
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• 2012

본 연구의 목적은 벽면제트영역의 열전달증진을 위해 직삼각형 로드 및 정사각형 로드를 충돌판앞에 배열한 후 로드와 충돌판 사이의 간극을 변화시키면서 열유동 특성을 실험적으로 검토한 것이다. 열전달증진율은 천이영역인 H/B=10보다는 포텐셜코어영역인 H/B=2에서 더 높게 나타났다. 본 실험범위에서 최대 열전달증진율은 직삼각형 로드를 설치할 때(H/B=2, C=1mm인 조건) 로드가 없는 평판과 비교하면 평균 약 46% 높게 나타났다. 그리고 직삼각형 로드와 정사각형 로드의 열전달증진율을 비교하면 간극 변화와 관계없이 직삼각형 로드가 정사각형 로드보다 평균 약 3~8% 정도 높게 나타났다.

• 기계저널
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• 제34권4호
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• pp.262-276
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• 1994

본 연구를 통하여 3차원 LDV 시스템의 측정기법을 개발하였으며, 측정결과의 신뢰성을 확인하 였다. 또한 이것을 타원제트 연구에 적용함으로써 그 응용 가능성을 확인하였다. 앞으로 3-D LDV 시스템을 사용하여 신뢰성 있는 측정결과를 얻기 위해서는 아래에 기술한 몇 가지 사항을 고려하여야 한다. 1) 3차원 레이저 유속계는 정교하고 복잡한 광학시스템으로 정확한 배열을 요구한다. 광학계와 실험장치의 좌표축이 일치하지 않으면 축방향보다 측방향(lateral) 속도변동 성분에 큰 영향을 준 다. 2) LDV 측정에서 속도편심을 줄이기 위해서는 적당한 출력의 레이저, 적절한 신호처리(signal conditioning), 실험조건에 알맞는 입자를 선정하여야 한다 3) 입자를 연속적으로 균일하게 공급하여야하며 신호분석기 조작에 익숙하여 도플러신호의 질을 최적화하여야 한다.

• 대한기계학회논문집B
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• 제24권2호
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• pp.204-213
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• 2000

This study deals with jet impingement, which is extensively used in the process industries to achieve intense heating, cooling or drying rates and also widely employed as a test flow for turbulent models due to its complex flow configuration, on a flat plate by numerical methods. In this calculation, the finite volume method was employed to solve the Navier-stokes equation based on the non-orthogonal coordinate with non-staggered variable arrangement. To get a better understanding for the fluid flow and heat transfer characteristics of the turbulent jet impingements, $k-{\varepsilon}-{\overline{v^{'2}}}$ turbulent model was adapted and compared with the experimental data and the result of standard $k-{\varepsilon}$ turbulent model. Numerical calculations were carried out with various flow rates, nozzle to plate distances. In the case of the axisymmetric jet impingement on a flat plate, $k-{\varepsilon}-{\overline{v^{'2}}}$ turbulent model showed better agreement with the experimental data than the standard $k-{\varepsilon}$ turbulent model in the prediction of the mean velocity profiles, the turbulent velocity profiles. the turbulent shear stress and the heat transfer rate. The highest heat transfer rate can be obtained when the impingement occurs within the potential core..

• 융복합기술연구소 논문집
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• 제5권1호
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• pp.27-31
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• 2015

A Pin-fin array is widely used to enhance the heat transfer in the internal cooling passage. The heat transfer distribution around the pin-fin is varied by the horseshoe vortex and flow separation. The difference of heat transfer coefficient induces the large thermal stress, which is one of the major reasons to break of hot components. So, it is required to enhance the heat transfer on the back side of pin-fin to solve the thermal stress problem. This study suggests the pin-fin with inclined jet hole and complex pin-fin/dimple array to enhance the heat transfer on the back side of pin-fin. The heat transfer coefficient is predicted by the numerical analysis, which is performed by CFX 14.0. The numerical results are obtained at Reynolds number, 10,000. The results show that the heat transfer on the back side of pin-fin is increased in both cases. Beside, the wake, which comes from dimple and jet, helps to develop the horseshoe vortex and increase the heat transfer on the next row pin-fin.