• International Journal of Fluid Machinery and Systems
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• 제9권4호
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• pp.382-393
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• 2016

Flow over a bluff body is an attractive research field in thermal engineering. In the present study, laminar flow over a confined heated square cylinder using CuO-Water nanofluid is considered. Unsteady two-dimensional Navier-Stokes and energy equations are solved numerically using finite volume method (FVM). Recent correlations for the thermal conductivity and viscosity of nanofluids, which are function of nanoparticle volume fraction, temperature and nanoparticle diameter, have been employed. The results of numerical solution are obtained for Richardson number, nanoparticle volume fractions and nanoparticle diameters ranges of 0-1, 1-5% and 30-100 nm respectively for a fixed Reynolds number of Re = 150. At a given volume concentration, the investigations reveal that the decreasing in size of nanoparticles produces an increase in heat transfer rates from the square cylinder and a decrease in amplitude of the lift coefficient. Also, the increment of Nusselt number is more pronounced at higher concentrations and higher Richardson numbers.

• 한국추진공학회지
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• 제22권5호
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• pp.115-124
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• 2018

전북대학교 고온플라즈마응용연구센터에서는 지구 재진입 및 고온재료의 열부하 평가를 위해 0.4 MW 급 아크가열플라즈마 풍동을 이용한 내열재료의 삭마 거동 등을 연구해 오고 있다. 아크가열 플라즈마 풍동은 고엔탈피 플라즈마를 발생시켜 다양한 고열부하의 극한 환경을 만들어 낸다. 이를 위해서는 플라즈마 토치내에 공기유량과 입력전류 등을 조절하여 다양한 열유속을 형성한다. 본 연구는 0.4 MW 아크가열 플라즈마 풍동의 다양한 방전 특성에 대해 조사하였다.

• 한국해양공학회지
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• 제31권6호
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• pp.425-430
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• 2017

In order to reduce the cost of corrections and time needed for the block assembly process, the reverse setting method is applied for a back-heated block to neutralize deck deformation. The proper reverse setting shape for a back-heated block to correct deformation improved the deck flatness, but an excessive amount of reverse setting could inversely affect the flatness of the block. A prediction method was developed for the proper reverse setting shape using a back-heated block, considering the complex geometry of blocks, thickness of the deck plate, and thermal loading conditions such as welding and back-heating. The prediction method was developed by combining the re-meshing technique and inherent strain-based deformation analysis using the finite element method. Because the flatness deviation was decreased until the lower critical point and thereafter it tended to increase again, the optimum value for which the flatness was the best case was selected by repeatedly calculating the predefined reverse setting values. Based on this analysis and the study of the back-heating deformation of large assembly blocks, including the reverse setting shape, the mechanism for selecting the optimum reverse setting value was identified. The developed method was applied to the actual blocks of a ship, and it was confirmed that the flatness of the block was improved. It is concluded that the developed prediction method can be used to predict the optimum reverse setting shape value of a ship's block, which will reduce the cost of corrections in the construction stage.

• 태양에너지
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• 제14권2호
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• pp.51-60
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• 1994

본 연구에서는 Furan foundry sand 유동층에서 유동화 특성과 Single spiral coil tube에 대한 열전달 특성을 실험하였으며, 전열관의 Pitch와 직경의 비(p/Do=1.58, 2.37, 3.17, 4.75) 및 전열관의 Pitch와 유동입자 크기의 비(p/dp=21.25, 25.15, 30.18, 35.93)가 전열특성에 미치는 영향을 실험적으로 연구하였다. 그 결과 다음과 같은 결론을 얻었다. 1) p/Do가 증가 할수록 평균 열전달계수는 증가한다. 2) 평균 Nusselt수의 증가율은 p/Do=4.75일 때보다 1.58 일 때가 더 크다. 3) 평균 Nusselt수와 Re수, $Pr_g$수 및 p/dp의 상관 관계식은 다음과 같이 나타낼 수 있었다. $Nu_{mean}=C\;Re^m\;Pr_g^{0.4}(p/dp)^n$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1560-1565
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• 2003

Thermocapillary convection in an open cylindrical annulus heated from the inside wall is investigated by two-dimensional numerical simulations. The deformable free surface is obtained as a solution of the coupled transport equations at fixed Prandtl and aspect ratio. Only steady convection can be realized in this axisymmetric computations with either non-deformable or deformable surfaces. Dynamic free-surface deformations do not induce transitions to oscillatory convection even at large Reynolds numbers. Free surfaces are convex near the cold wall due to the stagnation point, and concave near the hot wall. Free surface deformation increases with increasing Ca at a fixed Re. Two peaks appear at the free surface with low Re, while additional ripples, four peaks, occur at larger Re. Thermocapillary convection in the open annulus interior is insensitive to variations in Ca.

• 대한기계학회논문집B
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• 제33권12호
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• pp.983-991
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• 2009

The heat transfer phenomenon was investigated in this study when a circular water jet with low velocity flows to the downward facing heated circular plate and against the direction of gravity. Data are presented for jet flow rate between 0.23 and 2.3 l/min, jet fluid temperature of 24$^{\circ}C$, heat fluxes between 345 and 687 W/m$^2$, H/D=1, 2 and 3 with a single round jet diameter 2mm. The effects of heat flux, jet velocity and H/D on the local heat transfer are investigated in for the various regions of jet impingement. The local heat transfer distributions are analyzed based on the visualization of jet flow field. Data from experimental results are correlated by expressions of the form Nu=0.01$Re^{0.58}{\cdot}Pr^{0.4}$.

• 한국광학회지
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• 제1권2호
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• pp.135-141
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• 1990

레이저로 가열된 두께 160$\mu\textrm{m}$의 얇은 Si의 비선형 광학적 성질을 들띄움-탐사방법(pump-probe method)으로 조사하였다. 펄스폭은 180$\mu$sec이고 $TEM_{00}$-mode의 맥동형 Nd-YAG 레이저로 Si을 가열하였고, 발생하는 온도증가는 Si의 band gap 근처의 파장을 갖는 탐사광의 투과도변화를 관찰하여 측정하였다. Si의 온도상승은 입사된 레이저 광도에 비례함을 알 수 있었고, 실험상 최대 광대 25KW/$\textrm{cm}^2$의 레이저 빛살입사에 의해 $16^{\circ}C$의 온도상승을 관찰하였다. 이 결과로부터 Nd:YAG 레이저 파장에서의 온도변화에 따른 Sㅑ의 3차 비선형 광학계수 $\chi{(3)}$은 $6.6\times10^{-5}$로 산출되었다.

• Journal of Dairy Science and Biotechnology
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• 제19권1호
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• pp.13-21
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• 2001

Milk can be regarded as a complete food, containing protein, fat, lactose, vitamins and minerals. Milk is heated for a variety of reasons. The main reasons are: to remove pathogenic organisms; to increase shelf-life. But, when milk is heated, many changes take place: denaturation of whey proteins and interaction with casein, Maillard browning, losses of vitamin and minerals. The addition of a additive and milk powder to flavor and taste may cause undesirable change of quality during heating milk. The reconstituted milk is the milk product resulting from the addition of water to the dried or condensed form in the amount necessary to re-establish the specified water solids ratio. Therefore, according to the increasement of consumption of processed milk, the necessity for study about the quality of processed milk mixed with reconstituted milk arose.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.158-163
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• 2003

This paper assesses the two-equation turbulence models available in a commercial code, FLUENT, for heat transfer in a turbulent heated pipe flow. In case of flow under $Re_D=10,000$, Standard $\kappa-\epsilon$ and Realizable $\kappa-\epsilon$ models overpredict the Nusselt number about $20\%$ compared with the experimental correlation, and RNG $\kappa-\epsilon$ model overpredicts about $30\%$ when the two-layer zonal method is employed. When wall function method is adopted, all $\kappa-\epsilon$ models show better predictions. Standard $\kappa-\omega$ and SST $\kappa-\omega$ models have the dependency on the first grid point ($0.3). As Reynolds number becomes high, the predictions of all $\kappa-\epsilon$ and $\kappa-\omega$ models are in a good agreement with the experimental correlation.

• 설비공학논문집
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• 제14권7호
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• pp.592-598
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• 2002

The characteristics of a pulsating flow field from a heated block representing heat-dissipating electronic component in a channel have been numerically investigated. At the channel inlet a pulsating sinusoidal flow is imposed. The Reynolds number based on the channel height (H) is fixed at Re=500, and the forcing frequency is varied in the range of $0\leqSt\leq2$. Numerical results on the time-dependent flow field are obtained and averaged over a cycle of pulsation. The effect of the important governing parameters such as the Strouhal number is investigated in detail. The results indicate that the recirculating flow behind the block is substantially affected by the pulsation frequency. To characterize the periodic vortex shedding due to the inflow pulsation, numerical flow visualizations are carried out.