• Journal of computational fluids engineering
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• v.15 no.1
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• pp.46-55
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• 2010

In this study, the heat transfer and fluid flow characteristics of a condenser for a refrigerator are analyzed with the numerical method. The main objective of the study is to obtain basic data in order to develop a new type of condenser focused on an influence of thermal resistance of air side and thermal contact resistance on the heat transfer performance. The CFD technique was used for whole study, and experiments were performed in order to verify the reliability of the numerical analysis and predict the thermal contact resistance. In this study, a heat exchanger sample was made of a part of condenser to make the experimental and numerical analysis simple and efficient. Water was used for the inner working fluid of the heat exchanger, and an experimental apparatus was composed concisely. A heat exchanger sample of tube type was used to verify the reliability of numerical analysis, and a heat exchanger of fin and tube type was used to predict the ratio of thermal contact resistance to the overall thermal resistance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.4
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• pp.642-653
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• 1995

An analysis is made of the laminar fluid flow and heat transfer characteristics in a parallel-plate channel to whose walls are fitted with a series of equidistant staggered fins placed transversely to the flow direction. The governing equations are solved numerically by a finite-volume method for elliptic flows. Based on the obtained solutions of flow and temperature fields, the effects of Reynolds number and various geometric parameters on the heat transfer performance and pressure drop are evaluated. A comparson of the heat transfer characteristics between the channels with and without staggered fins is also made.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1626-1630
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• 2015

This paper reflected the Temperature test value and compare the Computational Fluid Dynamic analysis value on particular characteristics of the multi-winding transformer's cooling apparatus equipped by heat pipe with excellent heat transfer ability on design Particularly if you look at multi-winding transformers that supply high-quality Direct current power to silicon production apparatus, heat generation due to high current supply is excessive thus, an innovative cooling apparatus is required in particular for reduced size transformer.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.25-33
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• 2005

When a circular tube with uniform heat generation within the wall was placed in a cross flow, heat flows by conduction in the circumferential direction due to the asymmetric nature of the fluid flow around the perimeter of the circular tube The circumferential heat flow affects the wall temperature distribution to such an extent that. in some cases, significantly different results may be obtained for geometrically similar surfaces. In the present investigation, the effect of circumferential wall heat conduction is investigated for forced convection around circular tube in cross flow of air and water Two-dimensional temperature distribution $T_w(r,{\theta})$ is calculated through the numerical analysis. The difference between one-dimensional and two-dimensional solutions is demonstrated on the graph of local heat transfer coefficients. It is observed that the effect of working fluid is very remarkable.

• The KSFM Journal of Fluid Machinery
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• v.4 no.1 s.10
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• pp.14-21
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• 2001

In a small centrifugal compressor system, a high-speed motor needs to be developed to drive impellers directly. Heat is generated by both electrical heating due to copper coil resistance and aerodynamic heating in the gap between the rotor and stator in a high-speed motor. Removal of the heat is essential to the design of such motors since most magnetic materials are brittle and can be easily fractured by the heat. In the present study the cooling flow fields and temperature distributions are analyzed by using computational fluid dynamics simulation for a high-speed motor which has air cooling system as well as water cooling system. In the analysis, a conjugate heat transfer problem is solved by considering both convective heat transfer in the cooling system and conduction heat transfer in solid parts. Based on design drawings of a motor, air cooling system and water cooling system are analyzed to obtain temperature field and thus to check the coiling system performance. Also the cooling performance are studied for various flow rates of cooling air and water at the inlets.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.1
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• pp.1-9
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• 2003

The examinations of the operating mechanism of an oscillating capillary tube heat pipe (OCHP) using the visualization method revealed that the working fluid in the OCHP oscillated to the axial direction by the contraction and expansion of vapor plugs. The contraction and expansion were due to the formation and extinction of bubbles in the evaporating and condensing part, respectively The actual physical mechanism, whereby the heat which was transferred in such an OCHP was complex and not well understood. In this study, a theoretical model of the OCHP was developed to model the oscillating motion of working fluid in the OCHP. The differential equations of two-phase flow were applied and simultaneous non-linear partial differential equations were solved. From the analysis of the numerical results, it was found that the oscillating motion Of working fluid in the OCHP was affected by the operation and design conditions such as the heat flux, the charging ratio of working fluid and the hydraulic diameter of flow channel. The simulation results showed that the proposed model and solution could be used for estimating the operating mechanism in the OCHP.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.91-102
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• 2015

Analytical solutions for the forced convection heat transfer of viscoelastic fluids obeying the Giesekus model are obtained in a concentric annulus under laminar flow for both thermal and hydrodynamic fully developed conditions. Boundary conditions are assumed to be (a) constant fluxes at the walls and (b) constant temperature at the walls. Temperature profiles and Nusselt numbers are derived from dimensionless energy equation. Subsequently, effects of elasticity, mobility parameter and viscous dissipation are discussed. Results show that by increasing elasticity, Nusselt number increases. However, this trend is reversed for constant wall temperature when viscous dissipation is weak. By increasing viscous dissipation, the Nusselt number decreases for the constant flux and increases for the constant wall temperature. For the wall cooling case, when the viscous dissipation exceeds a critical value, the generated heat overcomes the heat which is removed at the walls, and fluid heats up longitudinally.

• The KSFM Journal of Fluid Machinery
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• v.10 no.3 s.42
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• pp.39-46
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• 2007

This study presents a numerical procedure to optimize the shape of staggered dimple surface to enhance turbulent heat transfer in a rectangular channel. The RBNN method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to-dimple print diameter (d/D), channel height-to-dimple print diameter ratio (H/D), and dimple print diameter-to-pitch ratio (D/S) are chosen as design variables. The objective function is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Latin Hypercube Sampling (LHS) is used to determine the training points as a mean of the design of experiment. The optimum shape shows remarkable performance in comparison with a reference shape.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.3
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• pp.8-17
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• 2015

In this research, low fidelity air/heat load analysis was conducted for the intake of high speed vehicle. For air/heat load calculations, aerodynamic properties at the surface and the boundary layer edge were estimated using Taylor-Maccoll equation for conical flow, shockwave relation and Prandtl-Meyer expansion equation for internal and external flow. Couette flow assumption and Reynolds analogy were used in order to calculate convective heat transfer coefficient. In order to calculate skin friction coefficient for heat transfer coefficient analysis, Van Driest method II and Reference Enthalpy method were considered. An axis symmetric SCRAMJET model was selected as a reference configuration for verifying the proper implementation of the present method. Comparison of the results using the present method and Computational Fluid Dynamic analysis showed that the present method is valuable for efficiently providing pressure and heat loads for air-intake structure design of the high speed air vehicle.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.5
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• pp.191-195
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• 2018

By using an ANSYS product suite (CFX, Ansys Multiphysics), which is a powerful tool for multiphysics analysis of complicated physical phenomena, we performed a structural stress analysis based on fluid flow and heat transfer phenomena within a quick connect/disconnect (QC/DC) bellows system. Considering the extremely low temperatures in the QC/DC environment, an approach to the problem based on complex multi-physics phenomena, where different phenomena interact with each other, is crucial. Therefore, we use a numerical analysis technique where fluid-thermal-structural interactions are combined. In conclusion, when low temperature fluids flow inside bellows, the expected service life is conspicuously reduced due to the thermal stress caused by heat transfer. Therefore, in future research, a structure with considerably reduced thermal stress by robust design optimization will be derived.