• 대한기계학회논문집B
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• 제23권1호
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• pp.149-157
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• 1999

Heat transfer in a duct is augmented remarkably by rib turbulators. However, increasing friction loss is accompanied due to ribs disturbing flows. Hence, pressure drops and heat transfer are considered simultaneously to decide heat/mass transfer performance in a rib-roughened duct. In the present study, the effects of rib cross section shape on pressure drop through a duct are investigated as well as those on heat transfer characteristics. The results show that the characteristics of heat/mass transfer and friction loss in the duct roughened with triangular ribs are similar to those with square ribs, while significantly different from those with semicircular ribs. The best performance in the duct is obtained by using semicircular shaped ribs among three types of ribs for the large rib angles of ${\alpha}{\geq}63^{\circ}$.

• 동력기계공학회지
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• 제15권5호
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• pp.43-48
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• 2011

The article represents an experimental investigation on friction and turbulent flow characteristics of free airflow through a rectangular duct fitted with semicircular ribs of uniform height (e = 3.5 mm) on one principle wall. The aspect ratio of the rectangular duct was AR= 5 where the duct height (H) was of 30 mm. Four different rib pitches (P) of 28 mm, 35 mm, 42 mm and 49 mm were used for constant rib height to hydraulic diameter ratio (e/Dh = 0.07) and constant rib height to channel height ratio (e/H = 0.11). The experimental results show some significant effects on pressure drop as well as turbulent characteristics at various configurations among different numbers of rib arrangements varying Reynolds number in the range of 15000 to 30000. Pressure transducer and hot wire anemometer were used for data acquisition of this experiment.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.697-698
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• 2002

The dispersion of an aerosol bolus in acinus is analyzed numerically. Model geometry is a straight duct surrounded by an axisymmetric semicircular annulus which is expanding or contracting with breathing. Unsteady Wavier-Stokes equation is solved by CFX-F3D, an FVM commercial code and the trajectory of massless particle Is computed by Lagrangian method. For steady flow with no wall motion, mean velocity of aerosol bolus in alveolated duct is a little smaller than that in straight duct and dispersion in alveolated duct is comparable with the dispersion in straight tube. For expanding duct mean velocity of aerosol bolus approaches half of that in straight tube and effective diffusivity is smaller than that of straight tube. For contracting duct mean velocity of aerosol bolus becomes slightly larger than that in straight tube and effective diffusivity is comparable with the case of straight tube.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.582-587
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• 2016

연료효율에 대한 선주들의 요구와 그린쉽이라는 사회적 흐름에 맞춰 현재 연료 절감 장치에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 KVLCC2M의 반류개선 및 연료효율 증가를 위한 반원형 덕트의 변수 연구를 진행하였으며, 계산의 신뢰도를 검증하기 위해 서울대학교 선박저항성능 연구실에서 실시한 모형 시험결과와 비교하였다. 반원형 덕트의 크기와 길이방향 위치를 설계변수로 설정하여, 총 12가지 경우에 대한 CFD 계산을 시행하였으며, 계산 결과를 유동 정류를 통한 저항 감소와 반류 개선을 통한 프로펠러의 성능 개선 이라는 두 가지 기준으로 최적 조건을 선정하였다. 또한, 후처리를 통해 계산 결과를 추가적으로 분석하여 에너지 절감의 이론적인 배경을 찾았으며, 이를 바탕으로 반원형 덕트를 개선하여 부채꼴형 덕트를 새로이 설계하였다. 이에 대한 추가적인 계산 결과 최대 4%의 연료절감 효과를 최종 확인하였다.