• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.06a
• /
• pp.391-392
• /
• 2008

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.7
• /
• pp.879-886
• /
• 2004

A numerical optimization has been carried out to determine the shape of the three-dimensional channel with oblique ribs attached on both walls to enhance turbulent heat transfer. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer. Shear stress transport (SST) turbulence model is used as a turbulence closure. Numerical results fur heat transfer rate show good agreements with experimental data. four dimensionless variables such as, rib pitch-to-rib height ratio, rib height-to-channel height ratio, streamwise rib distance on opposite wall to rib pitch ratio, and the attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related coefficients with a weighting factor. D-optimal method is used to determine the training points as a means of design of experiment. Sensitivity of the objective parameters to each design variable has been analyzed. And, optimal values of the design variables have been obtained in a range of the weighting factor.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.408-413
• /
• 2001

Numerical analysis on the three-dimensional laminar flows (Re=1000) and heat transfer in a rectangular channel with punched longitudinal vortex generator have been conducted to explore the heat transfer enhancement and the combined effect of the angle of attack ${\alpha}$ and the lovour angle ${\beta}$. Rectangular winglets have been used as vortex generators. Velocity and temperature fields and spanwise averaged Nu and friction factor were presented. Enhancement of heat transfer and flow loss penalty are evidenced. The results show performance characteristics allowing a reduction in heat transfer surface area of 62% for fixed heat duty and for fixed pumping power compared with that of channel flow without vortex generator. However, adding lovour angle to the vortex generator shows no positive effect on the heat transfer enhancement.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.31 no.1
• /
• pp.107-119
• /
• 1995

Turbulent flow characteristics and heat transfer in a three-dimensional room with a desk-type heat generating obstacle have been investigated numerically by the k-$\varepsilon$ two equation turbulence model. The room mole has one supply opening on the ceiling and two exhaust openings on the side walls. Th results of the flow structure and heat transfer have been represented for air for the inlet velocities in the range 0.1-10.0m/s. As the results of the three dimensional simulations, the relationships between mean Nusselt number and Reynolds number are clarified.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.5
• /
• pp.815-822
• /
• 2003

The ring rolling process involves not only three-dimensional non-steady material flow and continuous change of radius and thickness of the ring workpiece but also heat transfer among workpiece, rolls and environment. In this study, deformation and heat transfer analyses were conducted by using the three-dimensional thermo-rigid-plastic finite element method. Three cases of plain ring rolling process were, respectively, simulated for the predictions of roll forces and the highest temperature zone during the aluminum process that ductile fracture often occurs. In addition, to prevent fishtail phenomena of the ring workpiece, axial rolls were used for this study.

• Journal of Mechanical Science and Technology
• /
• v.19 no.7
• /
• pp.1488-1502
• /
• 2005

A three dimensional model was developed to analyze the mold filling and solidification in the casting processes. The model uses the VOF method for the calculation of the free surface and the modified Equivalent Specific Heat method for the treatment of the latent heat evolution. The solution procedure is based on the SIMPLER algorithm. The complete model has been validated using the exact solutions for phase change heat transfer and the experimental results of broken water column. The three-dimensional model has been applied to the benchmark test and the results were compared to those from experiment, a two-dimensional analysis, and another three dimensional numerical model.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1999.10a
• /
• pp.231-235
• /
• 1999

Cooling characteristics of cooling jacket for spindle system with built-in motor are studied. for the analysis, three dimensional model for the cooling jacket is built by using finite volume method. The three dimensional model includes the estimation on the amount of heat generation of bearing and built-in motor and the thermal characteristic values such as heat transfer coefficients on the boundary. The temperature distributions and the cooling characteristics are analyzed by using the commercial software FLUENT. Numerical results show that stream-wise cross section area and flow rate are important factors for cooling characteristics of cooling jacket. Cooling performance of cooling jacket is good in condition that stream-wise cross section's horizontal length is close to its vertical one and flow rate is high. This results show that heat transfer is dominated by velocity profile and heat transfer area.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.8
• /
• pp.1046-1055
• /
• 2000

The flow and thermal phenomena in flat tubes of radiator are analyzed numerically. To predict the characteristics of heat transfer and pressure drop, the flow analysis program for three-dimensional complex geometry is developed, which adopted an non-staggered grid system and Cartesian velocities as dependent variables of the momentum equations. Using the developed program, the effect of tube specifications on the heat transfer characteristics is investigated for various flat tubes. From this study, the following results are obtained; (1) For the same hydraulic diameter($D_h{\doteq}5.2$mm), the Nusselt numbers of three basic modeis(D, J, and H-model) are 8.71, 8.92, and 10.58, respectively, and the pressure drops of D-, J-, and H-model are predicted as $-3.08{\times}10^{-2}\;Pa,\;-3.12{\times}10^{-2}\;Pa,\;and\; -3.98{\times}10^{-2}$ Pa, (2) In case of the same flat tube specification, the fins must be brazed at upper tube surface because the heat is more vividly transferred. Therefore, it is found that the H- model is the most effective tube as a heat exchanger and these results are used as a fundamental data for the design of tube.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.6
• /
• pp.42-50
• /
• 2010

The present analysis deals with a numerical procedure for optimizing the shape of elliptical dimples in a cooling channel. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis is employed in conjunction with the SST model for predictions of the turbulent flow and the heat transfer. Three non-dimensional geometric design variables, such as the ellipse dimple diameter ratio, ratio of the dimple depth to the average diameter, and ratio of the distance between dimples to the pitch are considered in the optimization. Twenty-one experimental points within design space are selected by Latin Hypercube Sampling. Each objective function values at these points are evaluated by RANS analysis and producing optimal point using surrogate model. The linear combination of heat transfer coefficient and friction loss related terms with a weighting factor is defined as the objective function. The results show that the optimized elliptical dimple shape improves considerably the heat transfer performance than the circular dimple shape.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.390-395
• /
• 2001

Cooling characteristics using convection and conduction heat transfer in a parallel channel with extruding heat sources are studied numerically. A two-dimensional model has been developed for numerical prediction of transient, compressible, viscous, laminar flow, and conjugate heat transfer between parallel plates with uniform block heat sources. The finite volume method is used to solve this problem. The considered assembly consists of two channels formed by two covers and one PCB which has three uniform heat source blocks. Five different cooling methods are considered to find efficient cooling method in a given geometry and heat source. The velocity and temperature fields, local temperature distribution along surface of blocks, and the maximum temperature in each block are obtained.