• Journal of Biosystems Engineering
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• v.11 no.1
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• pp.37-51
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• 1986

실린더로 부터 Prandtl수가 0.7인 주변공기로 전달되는 혼합대류 열전달현상이 Stream-Vorticitv 함수로 표시된 지배방정식으로 부터 유한차분법에 의해 분석되어졌다. Reynolds수와 Grashof수의 함수로서 혼합대류 열전달에서 Nusselt수의 값들이 조사되어 졌으며 이들로부터 순수자연대류와 혼합대류, 혼합대류와 순수강제대류사이의 범위를 정하였다. 그 외에도 본 연구에서는 실린더주변의 온도분포와, 공기속도분포, 속도분리점(Separation point), 마찰계수, 압력분포등이 조사되어졌으나 제 1편에서는 Nusselt수와 온도분포만이 연구결과로 주어 졌으며, 본시험의 이론적 결과치들은 발표된 실험치들과 잘 일치하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.618-624
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• 1986

Some studies on direct-contact condensation in cocurrent stratified flow of steam and subcooled water were reviewed. Several approaches have been performed to develop the condensation heat transfer coefficient relationshipo. The local Nusselt number is correlated in terms of the local water Reynolds and Prandtl numbers as well as the steam Froude number. In addition, a turbulence-centered model, developed principally for gas absorption in several geometries, is modified by using calculated interfacial paramters for the turbulent velocity and length scales. These approaches result in a fairly good agreement with the data, whereas, the turbulence-centered model is here rexcommened since it is based on the turbulent properties which may be closely related to the condensation phenemena.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.11-22
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• 1987

A plane buoyant jet discharged vertically upward into a crossflow is analyzed by numerical solution of the governing equations of continuity, momentum and constituent transport. The turbulent transport is modelled by the Prandtl's mixing length theory. In the numerical solution procedure, the governing equations are transformed by stream function and vorticity transport, non-dimensionalyzed by discharge velocity, slot width, and parameters representing flow characteristics, and solved by Gauss-Seidel iteration method with successive underrelaxation. The numerical experiments were performed for the region of established flow of buoyant jet in the range of discharge densimetric Froude number of 4 to 32 and in the range of velocity ratio of 8 to 15, which is the ratio of discharge velocity to crossflow velocity. Variations of velocities and temperatures, flow patterns and vorticity patterns of receiving water due to buoyant jet were investigated. Also investigated are the effects of velocity ratio and discharge densimetric Froude number on the trajectories of buoyant jet. Computed are velocities, temperatures and local densimetric Froude numbers along the trajectory of the buoyant jet. Spreading rate and dispersion ratio were analyzed in terms of discharge densimetric Froude number, local densimetric Froude number and distance from the source along the jet trajectory. It was noted that the similarity law holds in both the profiles of velocity and temperatures across the jet trajectory and the integral type analysis of Gaussian distribution is applicable.

• Solar Energy
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• v.15 no.2
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• pp.47-64
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• 1995

An experimental investigation is carried out to see the local heat transfer characteristics of a rotating heated flat plate surface with constant heat flux when a normal water jet is impinging on this surface. The effects of jet Reynolds number, rotating Reynolds number are investigated while the distance between the nozzle and the flat plate is set fixed. As a result, correlations to relate the local Nusselt number to the local rotational Reynolds number, jet Prandtl number and the dimensionless radial position are presented.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.12 no.4
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• pp.201-202
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• 2008

Because of the importance of suction or injection in the fields of aerodynamics, space science and many other industrial applications, our present study is motivated. The effect of natural convection on MHD flow past a vertical plate with suction or injection is studied. We have tried to solve the dimensionless governing equations by using finite difference scheme. To ensure the validity of our numerical solutions, we have compared our numerical solutions for temperature and velocity for the case of suction and injection for unit Prandtl number with the available exact solutions in the literature. The corresponding codes were written in Mathematica 5.0 for calculating numerical solutions for temperature and velocity and the comparison between the exact and numerical solutions. For the purpose of discussing the results some numerical calculations are carried out for non-dimensional temperature T, velocity u, skin friction ${\tau}$ and the Nusselt number $N_u$, by making use of it, the rate of heat transfer is studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.1
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.423-430
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• 1998

Single phase heat transfer coefficients were measured for turbulent water flow in a micro-fin tube by using Wilson plot technique. An experiment for counterflow heat exchange between the micro-fin tube and its outer annulus passage was performed. The annulus side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a micro-fin tube were obtained by Wilson plot technique. Nusselt numbers based on the real heat transfer area and the nominal area were about 35% and 50% larger than those for smooth tube respectively Also, single-phase heat transfer correlations based on real heat transfer area and nominal area have been proposed for a micro-fin tube.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.20 no.4
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• pp.355-374
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• 2016

This work is devoted to investigate heat and mass transfer effects on MHD natural convection flow past an inclined plate with ramped temperature numerically. The dimensionless governing equations for this investigation are solved by using finite element method. The effects of angle inclination, buoyancy ratio parameter, permeability parameter, magnetic parameter, Prandtl number, heat generation, thermal radiation, Eckert number, Schmidt number, chemical reaction parameter and time on velocity, temperature and concentration fields are studied and presented with the aid of figures. The effects of the pertinent parameters on skin friction, rate of heat transfer and mass transfer coefficients are presented in tabular form. The numerical results are compared graphically with previously published result as special case of the present investigation and results found to be in good agreement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3196-3207
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• 1993

A second moment turbulent closure for the turbulent heat flux near a wall is developed by modification of model constants in pressure interaction term as the variables of the turbulent Reynolds number using the universal properties of turbulent heat flux near the wall. The present model shows that model constant for the wall reflection term in pressure interaction is most important in modelling of the near wall heat flux. Fully developed pipe flows with constant wall heat flux are tested to validate the proposed model. In most of calculation region, the predicted turbulent properties agree better with the experimetal data than the results from standard algebraic heat flux model which use the uniform model constants.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2274-2279
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• 2008

This paper numerically investigates thermo-flow characteristics of offset strip fins to obtain a correlation of heat transfer and pressure drop. The flow is divided into three regimes, i.e. laminar, transition and turbulent. The predicted j and f values from the SST k-w turbulence model agree with previous correlations with the error less than 20% in transition and turbulent regimes. Prandtl number is varied from 0.5 to 40 and a correlation to predict heat transfer and pressure drop for offset strip fins is suggested.