• 해양환경안전학회지
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• 제8권1호
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• pp.101-108
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• 2002

This experimental study was performed to investigate internal flow and unsteady flow characteristics using a model for actual shape of a Plate heat exchanger and visualization of flow through the particle image velocimetry. Seven Reynolds numbers were selected by calculation with the height of grooved channel and sectional mean velocity of inlet flow in the experiment, and instantaneous velocity distributions and flow characteristics were experimently investigated. The triangular grooved channel had a compound flow consisting of the flow in lower channel and the groove flow receiving shear stress by the channel flow in the experiment. The sheared mixing layer, in the boundary between the triangular groove and the channel. affected main flow to raise turbulent in the channel.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2005년도 추계학술대회지
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• pp.159-163
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• 2005

채널 내부의 비정상 흐름을 규명하기 위하여 실제 사용 중인 판형 열교환기 모델을 대상으로 가시화 실험과 입자영상유속계(PIV)를 사용한 계측을 수행하였다. 실험은 기복을 가지고 있는 채널의 높이와 내부유동의 부분 평균속도벡터에 따른 7가지 종류의 레이놀즈수를 적용하였고, 순간속도벡터분포와 유동특성을 고찰하였다. 실험에서 삼각형상 그루브 채널은 하부 채널과 채널 흐름에 의해서 받고 있는 전단응력의 그루브 흐름과의 관계에서 복합적인 흐름의 형태로 나타났다. 삼각형상 그루브와 채널 사이의 경계인 전단혼합층은 채널에서 난류강도가 상승하는 주흐름에 영향을 미쳤다.

• 설비공학논문집
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• 제16권4호
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• pp.324-331
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• 2004

Particle Image Velocimetry (PIV) measurements have been carried out to investigate the pulsatile flow characteristics in a triangular grooved channel. The results showed that a vortex was generated at the tip of the groove and flowed into the groove rotating inside during the acceleration phase of the main stream promoting the mixing of the fluid. Then, at the deceleration phase of the main stream, the vortex entrained fluid from the relatively slow moving main stream to grow bigger than the groove size. Finally the vortex was ejected to the main stream carrying the fluid away from the groove, resulting in the enhancement of mixing between the stagnant fluid in the groove and the main stream in the channel. It was found that the fluid mixing enhancement is maximized when the pulsatile period is the same as the time duration which the vortex takes to grow larger enough to fill the groove and to be ejected to the main stream.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.93-96
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• 2006

The heat transfer enhancement by pulsatile flow in the plate heat exchanger has been investigated numerically in the present study. The numerical study was performed in the range of the mass flux from 0.04 to 0.12 kg/s. The results showed that the pulsatile flow produces resonating vortex shedding at the groove sharp edges and a strong transient vortex rotation within the grooved channels. As a result, the mixing between the trapped volume in the grooved cavity and the main stream was enhanced. Good agreements between the predictions and measured data are obtained in steady flow. And the heat transfer of pulsatile flow is about 2.4 times than steady flow when frequency is 10 Hz and the mass flux of cold side is 0.04 kg/s.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.85-90
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• 2005

The heat transfer enhancement by pulsatile flow in plate heat exchanger has been investigated numerically in the present study. The numerical study was performed ill the range of the Strouhal number from 0.04 to 2 and the Reynolds number from 370 to 730. The results showed that the pulsatile flow produces resonating vortex shedding at the groove sharp edges and a strong transient vortex rotation within the grooved channels. As a result, the mixing between the trapped volume in the grooved cavity and the main stream was enhanced. Good agreements between the predictions and measured data are obtained for the optimum frequency of pulsation and corresponding heat transfer enhancement

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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• pp.412-412
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• 2006

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.317-322
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• 2005

This study is aimed to analyze the effects of heat pipe shape on the heat transfer in solar collector with a axial grooved heat pipe. In the design of a heat pipe. two of the most important criteria to be met are the operating temperature range and the maximum heat transport capacity, When the operating temperature range is known and the working fluid has been selected, the maximum heat transport capacity depends strongly on capillary pressure and liquid flow. The heat transport capacity of the heat pipe will depend on the geometry of the heat pipe, the wick structure. the vapor channel shape. groove number. cooling temperature. condenser length and pipe diameter. So various shapes are used for mathematical models of two-phase flow in grooved heat pipe. From the results. the adequate groove shape and scale are presented by considering the heat transport and capillary limitation.

• 설비공학논문집
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• 제13권10호
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• pp.1009-1016
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• 2001

The heat transfer enhancement by pulsatile flow in a triangular grooved channel has been experimentally investigated in this study The experiment was performed in the ranges of the Reynolds number from 270 to 910, the pulsatile fraction from 0.125 to 0.75, and the Strouhal number from 0.084 to 0.665. It was measured that the heat transfer improves up to 350% compared with the steady flow case at Re=270,$\eta=0.5$, and St=0.335. The heat transfer enhancement was found to increase as the pulsatile fraction increases and the Reynolds number decreases. It was also found that the heat transfer enhancement is maximized at a specific pulsatile frequency satisfying the resonant condition. The nondimensional frequency, i.e., the Strouhal number at the resonant condition was found to increase as the Reynolds number decreases. The flow visualization revealed that the heat transfer enhancement results from the strong mixing caused by the repeating sequence of vortex formation, rotation and subsequent ejection from the grooves by the pulsatile flow.