• 설비공학논문집
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• 제13권5호
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• pp.398-410
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• 2001

The flow and heat transfer characteristics for three-dimensional mixed convection flows in a radiator flat tube with U--shaped grooves are analyzed numerically. The flow and temperature fields are calculated by using the modified SIMPLE algorithm for irregular geometry. One tube specification among the various flat tube exchangers is recommended by considering the heat transfer and pressure drop. The effects of variation of coolant flow conditions and external air conditions on the flow and the thermal characteristics for the selected tube are investigated. the results show that inlet velocity of coolant flow is the very important factor in heat transfer and pressure drop, and top side is better position than the others as fin cleave to tube.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 춘계 학술대회논문집
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• pp.172-177
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• 2000

In this numerical work, three dimensional supersonic laminar flow and heat transfer of a blunt body(sphere-cone) at Mach 5 is simulated. The effects of angle of attack and the spin rate on the now and heat transfer are analysed. To solve the three dimensional compressible Wavier-Stokes equation, a finite volume method with the modified LDFSS scheme is employed for spatial discretization, and a point SGS implicit method is used for time integration. It is found that the heat transfer rate increases at the windward side and decreases at the leeward side with the angle of attack. The heat transfer rate at all surfaces slightly increases with the spin rate.

• 설비공학논문집
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• 제8권4호
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• pp.561-575
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• 1996

The interaction of turbulent mixed convection and surface radiation in a three-dimensional channel with the heated blocks is analyzed numerically. Two blocks are maintained at high temperature and the other bottom and horizontal walls are insulated. S-4 method is employed to calculate the effect of the radiative heat transfer. The low Reynolds number k-$\varepsilon$ model proposed by Launder and Sharma is used to estimate the turbulent influence on the heat transfer enhancement. From above modeling, the effects of various channel specifications on the flow and heat transfer characteristics are investigated. The variables used for the present study are Reynolds number, block spacing, the channel height spacing for block and the emissivity. Average Nusselt numbers along the block surfaces are correlated and presented in terms of Reynolds number, emissivity and dimensionless geometric parameters. For the range of conditions in this study, average Nusselt numbers along the block surfaces are strongly influenced by the Reynolds numbers and channel height spacing for block but weakly influenced by the block spacing and the emissivity of the adiabatic walls.

• 대한기계학회논문집B
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• 제27권3호
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• pp.311-318
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• 2003

The present work evaluates the effects of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly. by obtaining velocity and pressure fields. turbulent intensity. flow-mixing factors. heat transfer coefficient and friction factor using three-dimensional RANS analysis. Four different shapes of mixing vane. which were designed by the authors were tested to evaluate the performances in enhancing the heat transfer. Standard k-$\varepsilon$ model is used as a turbulence closure model. and. periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant. but the twist angle of mixing vane is changed. The results with three turbulence models were compared with experimental data.

• 대한기계학회논문집B
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• 제23권1호
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• pp.1-11
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• 1999

The three-dimensional laminar mixed convection flow between the conductive printed circuit boards. on which the heat generating rectangular blocks are uniformly distributed, has been examined in the present study. The flow and heat-transfer characteristics are assumed to be pseudo periodic in the streamwise direction and symmetric in the cross-stream direction. Using an algorithm of SIMPLER, the continuity equation. the Navier-Stokes equations and the energy equation are solved numerically in the three-dimensional domain Inside the channel. The convective derivative terms are discretized by the QUICK scheme to accurately capture the flow field. The flow and the heat transfer characteristics are thoroughly examined for various Re and Gr.

• Journal of Mechanical Science and Technology
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• 제15권11호
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• pp.1555-1562
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• 2001

In a conventional shell-and-tube heat exchanger, fluid contacts with tubes flowing up and down in a shell, therefore there is a defect in the heat transfer with tubes due to the stagnation portions . Fins are attached to the tubes in order to increase heat transfer efficiency, but there exists a limit. Therefore, it is necessary to improve heat exchanger performance by changing the fluid flow in the shell. In this study, a highly efficient shell-and-tube heat exchanger with spiral baffle plates is simulated three-dimensionally using a commercial thermal-fluid analysis code, CFX4.2. In this type of heat exchanger, fluid contacts with tubes flowing rotationally in the shell. It could improve heat exchanger performance considerably because stagnation portions in the shell could be removed. It is proved that the shell-and-tube heat exchanger with spiral baffle plates is superior to the conventional heat exchanger in terms of heat transfer.

• Journal of Welding and Joining
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• 제9권2호
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• pp.37-43
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• 1991

In order to analyze the mechanical phenomena of three dimensional elato-plastic behavior caused by welding of thick plate, it is necessary to solve exactly the three dimensional unstationary heat conduction problem considering the moving effect of heat source and the temperature-dependence of material properties. In this paper, the three-dimensional unstationary heat conduction problem is formulated by using an isoparametric finite element method. Thereafter, the transient temperature distributions, according to time, of thick plate during welding are defined from the results calculated by the developed computer program.

• 대한기계학회논문집B
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• 제26권5호
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• pp.716-723
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• 2002

Heat transfer in linear motor driven stages for surface mounting device applications was investigated. A simple one-dimensional thermal resistance model (TRM) was introduced. In order to reduce three-dimensional nature to one-dimensional, a few assumptions and simplifications were employed suitably. A good agreement with a finite element heat transfer analysis in temperature profile was obtained. For validation, the analysis was compared with the measurement with respect to motor driving power. Overall discrepancy was less than 7$^{\circ}C$. The influence of two high thermal resistance parts, insulation sheet and thermal contact between the coil assembly and the mounting plate, was examined through the analysis. Additionally, the thermal resistance analysis was applied to another stage including an internal cooling-air passage, and was found available for this system as well. After validation, the cooling effect was surveyed in terms of motor power, and cooling-air and -water flow rate.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.96-101
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• 2001

Heat transfer in linear motor driven stages for surface mounting device applications was investigated. A simple one-dimensional thermal resistance model was introduced. In order to reduce three-dimensional nature to one-dimensional, a few assumptions and simplifications were employed suitably. A good agreement with a finite element heat transfer analysis in temperature profile was obtained. For validation, the analysis was compared with the measurement with respect to motor driving power. Overall discrepancy was less than $7^{\circ}C$. The influence of two high thermal resistance parts, insulation sheet and thermal contact between the coil assembly and the mounting plate, was examined through the analysis. Additionally, the thermal resistance analysis was applied to another stage including an internal cooling-air passage, and was found available for this system as well. After validation, the cooling effect was surveyed in terms of motor power, and cooling-air flow rate.

• KIEAE Journal
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• 제16권1호
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• pp.81-87
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• 2016

Purpose: Heat transfers phenomena are described by the second order partial differential equation and its boundary conditions. In a three-dimensional structure of a building, the heat transfer phenomena generally include more than one material, and thus, become complicate. The analytic solutions are useful to understand heat transfer phenomena, but they can hardly be applied in engineering or design problems. Engineers and designers have generally been forced to use numerical methods providing reliable results. Finite volume methods with the unstructured grid system is only the suitable means of the analysis for the complex and arbitrary domains. Method: To obtain an numerical solution, a discretization method, which approximates the differential equations, and the interpolation methods for temperature and heat flux between two or more materials are required. The discretization methods are applied to small domains in space and time, and these numerical solutions form the descretized equations provide approximated solutions in both space and time. The accuracy of numerical solutions is dependent on the quality of discretizations and size of cells used. The higher accuracy, the higher numerical resources are required. The balance between the accuracy and difficulty of the numerical methods is critical for the success of the numerical analysis. A simple and easy interpolation methods among multiple materials are developed. The linear equations are solved with the BiCGSTAB being a effective matrix solver. Result: This study provides an overview of discretization methods, boundary interface, and matrix solver for the 3-dimensional numerical heat transfer including two materials.