• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.33.2-33.2
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• 2005

• Journal of Advanced Marine Engineering and Technology
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• 제36권1호
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• pp.57-63
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• 2012

열전달 향상을 위하여 이차유동을 발생시켜 열전달을 증가시키는 방법에는 여러 가지가 있다. 본 연구에서는 수평채널에 딤플과 돌출을 설치하여 각각의 깊이와 높이를 변화시켰을 때의 압력강하 및 열전달 특성을 수치해석을 통하여 연구하였다. 딤플과 돌출은 수평채널의 윗면과 아래면 에 설치되었으며, 깊이 및 높이를 0.125, 0.25, 0.25, 0.3, 0.375로 하였다. 딤플의 경우, 후면부에서 높은 Nusselt 수가 나타났고 깊이가 커질수록 평균 Nusselt 수가 감소하였다. 돌출의 경우, 전면부에서 높은 Nusselt 수가 나타났고 높이가 커질수록 Nusselt 수가 증가하였다. 딤플과 돌출 모두 유속이 증가함에 따라 열전달이 향상되는 경향을 보였지만 성능계수는 감소하였다. 성능계수는 유속이 낮은 영역에서 가장 크게 나타났다.

• 대한기계학회논문집B
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• 제22권1호
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• pp.122-130
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• 1998

The present work analyzes the pressure drop and heat transfer characteristics of the plate heat exchanger with staggered dimples. The flow is assumed to be constant property, three dimensional and laminar. A thermal boundary condition is uniform wall temperature and it is assumed that the flow is periodically fully developed. Elliptic grid generation is used for proper modelling of the internal tube geometry with dimples. Computations have been carried out for a variety of geometric parameters, Reynolds number, and Prandtl number. The friction factor ratio and the ratio of a module average Nusselt number are presented for the cases considered in this study. It is found that the distance between dimples has a substantial effect on the pressure drop and heat transfer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2352-2356
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• 2008

Heat transfer and performance characteristics have been investigated for a rectangular wavy duct with dimple or protrusion arrays. The test duct was 15mm in height and 105mm wide. The print diameter of the dimple/protrusion wall was 12.99mm and the depth/height of the dimple/protrusion was 3.75mm. Local heat transfer coefficients on the dimple/protrusion wall were measured using a transient TLC technique. The Reynolds number was varied from 3,000 to 10,000. For the wavy duct tested in this study, adverse static pressure characteristics occurred at turning region of the wavy duct due to secondary flows. For the wavy duct with protrusion array, higher heat transfer enhancement level of 7.4 times than smooth straight case in maximum was obtained at low Reynolds number due to the high heat transfer enhancement by vortex flows. Also, the protrusion array increased the performance level of 3.0 at low Reynolds number of 3,000.

• 한국강구조학회 논문집
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• 제29권2호
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• pp.123-134
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• 2017

풍력발전 타워용 종방향 보강 원형단면 강재 쉘에 대하여 재료 및 기하학적 비선형 유한요소법(GMNIA)으로 극한압축강도 해석을 수행하였다. 보강 쉘의 반경 대 두께비, 초기변형 형상 및 진폭, 종방향보강재의 면적 및 간격 등의 주요 설계 파라미터가 압축력을 받는 보강 쉘의 극한강도에 미치는 영향을 분석하였으며, DNV 설계기준에 의한 설계좌굴강도와 유한요소해석으로 구한 극한압축강도를 비교하였다. 기하학적 초기결함의 형상은 선형 좌굴해석으로부터 구한 좌굴모드 및 제작 과정에서 용접으로 발생하는 딤플 변형을 고려하였다. 해석 대상 보강 쉘의 반경 대 두께비는 50~200이며, 종방향보강재는 횡비틀림좌굴과 국부좌굴이 발생하지 않도록 DNV 설계기준에 따라 두께와 돌출폭을 결정하였다.

• 설비공학논문집
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• 제23권12호
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• pp.805-814
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• 2011

In the present study, the detailed flow structure and heat transfer characteristics in the newly-designed heat transfer surface geometry were investigated. The surface geometry proposed in the present study is a traditional dimple structure combining with a protrusion inside the dimple, which is named a protrusion-in-dimple in this study. The basic idea underlying the present surface geometry is to enhance the flow mixing and the corresponding heat transfer in the flow re-circulating region generated by a conventional dimple cavity. The present study was performed by the direct numerical simulation at a Reynolds number of 2800 based on mean velocity and channel height and Prandtl number of 0.71. Three different protrusion heights for protrusion-in-dimples were considered as the main design parameter of the present study. The calculated pressure drop and heat transfer capacity were assessed in terms of the Fanning friction factor and Colburn j factor. The overall performances estimated in terms of the volume and area goodness factor for protrusion-in-dimple cases were higher than the conventional dimple case.