• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.489-492
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• 2006

The present work was performed to investigate the thermal and hydraulic characteristics of flow inside the plain and turbulator flat tubes for the automobile application. The pressure drop and heat transfer coefficient at laminar, transition and turbulent regimes were studied experimentally and numerically. The flow transition was confirmed by flow visualization and quantitative data. It is proposed equations for the friction and heat transfer coefficient in the fully developed laminar flow inside rectangular tube as function of aspect ratio.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.4
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• pp.27-33
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• 1995

The turbulent flow and heat transfer in the tunnel laminar flow type clean room is investigated by a numerical simulation. The model clean room is assumed to be a rectngular $5m\times3m$, in which a worktable of 0.75m hight, and 1.5m or 3m long at the floor. Major parameters are the inlet flow velocity, inlet hole size and worktable surface distance. The mean Nusselt number is increased by increasing Reynolds number and can be expressed by the correlation equation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.979-987
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• 1996

A theoretical study for the laminar round jet diffusion flame impinging on the wall was carried out to predict the characteristics and structure of impinging jet flame and heat transfer to the wall. Finite chemistry via Arrhenius equation was adopted as the combustion model. All the transport properties were considered as the variable depending on the temperature and composition. For the parametric study, the distance from nozzle to perpendicular wall and Reynolds number at nozzle exit were chosen as the major parameters. As the results of the present study, the characteristics of flow field and the distributions of temperature, density and each chemical species were obtained. The heat transfer rate from flame to the wall and the effective heating area were calculated to investigate the influence of the major parameters on the heat transfer characteristics.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.11 no.4
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• pp.1-5
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• 1982

In this paper, a study is made of the steady laminar free convection boundary-layer equations on a sphere with uniform surface heat flux. To solve the boundary-layer equations, well-known Pohlhausen's simiarity solution for vertical plates is adopted just the same for spherical bodies by introducing twonondimensional parametric functions, so called azimuth functions. To determine the values of the azimuth functions which are expressed in series at the two points (the upper stagnation point and the equator), trial and error method is required. It is concluded that the heat transfer results are in good agreement with obtained from perturbation method and Von Karman-Pohlhausen method within the steady laminar free convection region for Pr=0.70.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.676-682
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• 2002

The laminar convective heat transfer in ventilated space with various horizontal partitions was studied numerically and experimentally For the numerical study, the governing equations were solved by using a finite volume method for various numbers Re, Gr, Pr and partition numbers. The experimental study was conducted by using a holographic interferometer. The isotherms and velocity vectors have been presented for various parameters. As the number and length of partition increased, convective heat transfer decreased. Based on the numerical data, correlation equations were obtained for the mean Nusselt number in term of Gr/Re$^2$. In the region of Gr/Re$^2$$\leq$ 1, the mean Nusselt number was small, but in the region of Gr/Re$^2$> 1, the mean Nusselt number was constant.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.2
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• pp.204-215
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• 1987

Laminar natural convective heat transfer within a two-dimensional rectangular enclosure with horizontal conducting walls and partitions was investigated by numerical analysis and experiment. The enclosure consists of two isothermal vertical walls and two adiabatic horizontal walls. This combined heat transfer problem of conduction and natural convection was solved using finite difference method with SIMPLE algorithm, and temperature distribu-tions in the air filled enclosure was obtained using Mach-Zehnder interferometer. Good agree-ment was obtained between the predicted and measured results. The effect of geometric parameters and thermal properties on heat transfer was studied far Grashof numbers in range, $1\times10^4\;{\leqslant}\;G^r\;{\leqslant}\;6.4\times10^5.$ It was found that both velocity and temperature fields were in-fluenced significantly by thermal conductivity of the conducting walls and the partitions, and by geometry of partitions.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.463-466
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• 2002

In order to examine the possibility of using a cavity as a passive device for reduction of skin friction and heat transfer, an intensive parametric study over a broad range of the cavity depth and length at different Reynolds numbers is performed for both laminar and turbulent boundary layers in the present study. Direct and large eddy simulation techniques are used for turbulent boundary layers at low and moderate Reynolds numbers, respectively. for both laminar and turbulent boundary layers over a cavity, a flow oscillation occurs due to the shear layer instability when the cavity depth and length are sufficiently large and it plays an important role in the determination of drag and heat-transfer increase or decrease. For a cavity sufficiently small to suppress the flow oscillation, both the total drag and heat transfer are reduced. Therefore, the applicability of a cavity as a passive device for reduction of drag and heat transfer is fully confirmed in the present study. Scaling based on the wall shear rate of the incoming boundary layer is also proposed and it is found to be valid in steady flow over a cavity.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.425-436
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• 1987

Accurate predictions of heat transfer coefficient of vertical laminar film-boiling are very important in many engineering applications. There are many predictions, however they are not exact as yet, since they have used the assumption of constant thermodynamic properties in the analysis. In this paper, heat transfer of vertical film boiling was analysized by Runnge Kutta method using veriable thermodynamic properties. 1/4 interval method was exployed for the prediction of unknown wall boundary condition. Numerical computations were performed with varying the wall temperature and the free stream velocity of liquid. Results show that assumption of constant thermodynamic properties induced considerable error in predicting the heat transfer coefficient, friction factor, film thickness, and critical length for transition to turbulent flow. Comparision of the predicted heat transfer coefficient of present analysis with that from Bromley's correlation shows that the use of general latent heat in Bromely equation instead of modified latent heat is more desireable since it makes the coefficient of Bromley equation into constant.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.3 s.246
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• pp.238-245
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• 2006

This paper proposes appropriate conjugate parameters and dimensionless temperatures to analysis the conjugate problem of heat conduction in solid wall coupled with laminar film condensation flow adjacent to horizontal flat plate. An efficient methods for some fluids are proposed for its solution. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Modified Jacob number, $Ja^*/Pr$, defined by an overall temperature difference, a property ratio $\sqrt{\rho_l{\mu}_l/{\rho_v{\mu}_v}$ and the conjugate parameter $\zeta$. The obtained similarity solution reveals the effect of the conjugate parameter, and the results are compared with the simplified solution. The variations of the heat transfer rates as well as the interface temperature and frictions along the plate are shown explicitly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.774-782
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• 2004

This article presents a numerical and experimental investigation for the single-phase forced laminar convective heat transfer through arrays of micro-channels in micro heat exchangers to be used for cooling power-intensive semiconductor packages, especially the stacked multi-chip modules. In the numerical analysis, a parametric study was carried out for the parameters affecting the efficiency of heat transfer in the flow of coolants through parallel rectangular micro-channels. In the experimental study, the cooling performance of the micro heat exchanger was tested on prototypes of stacked multi-chip modules with difference channel dimensions. The simulation results and the experiment data were acceptably accordant within a wide range of design variations, suggesting the numerical procedure as a useful method for designing the cooling mechanism in stacked multi-chip packages and similar electronic applications.