• Journal of Advanced Marine Engineering and Technology
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• 제34권7호
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• pp.981-990
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• 2010

The main objective of this study is to investigate the fluid flow and the heat transfer characteristics of nanofluids using multi-phase thermal LBM and to realize theenhancement of heat transfer characteristics considered in the Brownian motion. In multi-phase, fluid component($H_2O$) is driven by Boussinesq approximation, and nanoparticles component by the external force gravity and buoyancy. The effect of Brownian motion as a random movement is modified to the internal velocity of nanoparticles(Cu). Simultaneously, the particles of both the phases assume the local equilibrium temperature after each collision. It has been observed that when simulating $H_2O$-Cu nanoparticles, the heat transfer is the highest, at the particle volume fraction 0.5% of the particle diameter 10 nm. The average Nusselt number is increased approximately by 33% at the particle volume fraction 0.5% of the particle diameter 10 nm when compared with pure water.

• 한국전산유체공학회지
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• 제3권2호
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• pp.27-38
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• 1998

Rotating flow of a stratified fluid contained in a circular cylinder with unstable temperature gradient imposed on the side wall of it has been numerically studied. The temperatures at the endwall disks are constant. The top disk of the container is coider than that of the bottob disk, as much as the temperature difference n${\Delta}$T, (0${\leq}$n${\leq}$3). Flows in the vessel are driven by an impulsive rotation of the hot bottom disk with respect to the central axis of the cylinder. Flow details have been acquired. For this flow, the principal balance in the interior core is characterized by a relationship between the radial temperature gradient and the vertical shear in the azimuthal velocity. As the buoyancy effect becomes appreciable, larger portions of the meridional fluid transport are long-circuit from the bottom disk to the interior region via the side wall.

• Journal of Advanced Marine Engineering and Technology
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• 제28권8호
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• pp.1251-1257
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• 2004

In order to analyze the heat transfer phenomena in the plasma flames, a mathematical model describing heat and fluid flow in an electric arc has been developed and used to predict heat transfer from the arc to the steel bath in a DC Electric Arc Furnace. The arc model takes the separate contributions to the heat transfer from each involved mechanism onto account, that is radiation, convection and energy transported by electrons. The finite volume method and a SIMPLE algorithm are used for solving the governing MHD equations, that are conservation equations of mass, momentum and energy together with the equations describing a standard k-${\varepsilon}$ model for turbulence. The model predicts heat transfer for different currents and arc lengths. Finally these calculation results can be used as a useful insight into plasma phenomena of the industrial-scale electric arc furnace. From these results, it can be concluded that higher arc current and longer arc length give high heat transfer

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.133-138
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• 2003

In this study, numerical investigation has been performed on the evolution of weld pool geometry with moving free surface during low-energy density laser welding process. The free surface elevates near the weld pool edge if ${\partial}{\sigma}/dT$ is dominantly negative. On the contrary, the free surface rise at the center of weld pool in case of mainly positive ${\partial}{\sigma}/dT$. The predicted weld pool width and depth with moving free surface are 5∼15%$5{\sim}15%$ greater than those with flat weld pool surface. It is considered that weld pool surface oscillation during melting process augments convective heat transfer rate in the weld pool.

• Journal of Magnetics
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• 제21권1호
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• pp.153-158
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• 2016

This paper aims to discuss the Non Darcy boundary layer flow of non-conducting viscous fluid with magnetic ferroparticles over a permeable linearly stretching surface with ohmic dissipation and mixed convective heat transfer. A magnetic dipole is applied "a" distance below the surface of stretching sheet. The governing equations are modeled. Similarity transformation is used to convert the system of partial differential equations to a system of non-linear but ordinary differential equations. The ODEs are solved numerically. The effects of sundry parameters on the flow properties like velocity, pressure, skin-friction coefficient and Nusselt number are presented. It is deduced the frictional resistance of Lorentz force decreases with stronger electric field and the trend reverses for temperature. Skin friction coefficient increase with increase in ferromagnetic interaction parameter. Whereas, Nusselt number decrease.

• 한국생산제조학회지
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• 제19권4호
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• pp.434-439
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• 2010

A compliant mechanism is a mechanism that produces its motion by the flexibility of some or all of its members when input force or thermal load is applied. Whereas the topology optimizations based on homogenization and SIMP parameterization have been successfully applied for compliant mechanism design, ESO approach has been hardly considered yet for the optimization of these types of systems. In this paper, traditional ESO method is adopted to achieve the optimum design of a compliant mechanism for thermal load, since AESO method cannot consider the effect of both heat conduction and convection. Sensitivity number, a criterion for element removal in traditional ESO, was newly defined for input thermal loading. The procedure has been tested in numerical applications and compared with the results obtained by other methods to validate these approaches.

• 태양에너지
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• 제6권2호
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• pp.62-69
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• 1986

An analysis is made of the fully developed laminar flow and heat transfer in a parallel flat plate with heated rectangular block arrays to investigated the influence of bouyancy force. The shrouds is considered as adiabatic, while the heated block surface transmit a uniform rate of heat flux per unit axial length. The governing equations for velocity and temperature are solved by SIMPLE(Semi-Implicit Method Pressure Linked Equation) algorithm. Detailed velocity and temperature fields and overall heat transfer on wide range of Rayleigh number and various aspect ratios of heated rectangular blocks are computed. The result show that bouyancy leads to a significient enhancement in heat transfer along with a smaller increase in pressure drop, with the great enhancement found when the aspect ratio is 3.0.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.138-139
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• 2007

This research provides machine designers with some intuition to consider both, magnetic and heat transfer effects. A topological multi-objective function includes magnetic energy and heat inflow rate to the system, which equals to the total heat dissipation by conduction and convection. For the thermal field regarding the heat inflow, introduced as a reaction force, topology design sensitivity is derived by employing discrete equations. The adjoint variable method is used to avoid numerous sensitivity evaluations. As a numerical example, a C-core design excited by winding current demonstrates the strength of the multi-physical approach.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권4호
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• pp.10-16
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• 2001

An experimental study for free convective heat transfer in a thermal diode type enclosure is presented. The thermal diode is a device which allows heat to be transferred in one direction by convection due to density difference of the fluid, and consists of a rectangular-paralle-logrammic enclosure with a guide vane. It is used as heat collection system of solar energy due to its simple construction and low cost. Experimental parameters were guide vane thickness, the inclination angles of the parallelogrammic enclosure, and the lengths of the rectangular enclosure part. The parameter range of the flux Rayleigh numbers was $2.4\times{10}^8$~$9.8\times{10}^8$. The heat transfer rate of this system was shown 10~47% higher than that of other earlier research results without the guide vane. The correlation for fixed $\phi=60^\circ$ was obtained, Nu=0.0037(Ra^*)^{0.429}(d^*)^ {0.050}(Lr/H)^{0.0415}$.

• Advances in concrete construction
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• 제10권4호
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• pp.357-367
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• 2020

The impulse of this paper is to examine the influence of unsteady flow comprising of Eyring-Powell nanofluid over a stretched surface. This work aims to explore efficient transfer of heat in Eyring-Powell nanofluid with bio-convection. Nanofluids possess significant features that have aroused various investigators because of their utilization in industrial and nanotechnology. The influence of including motile microorganism is to stabilize the nanoparticle suspensions develop by the mixed influence of magnetic field and buoyancy force. This research paper reveals the detailed information about the linearly compressed Magnetohydrodynamics boundary layer flux of two dimensional Eyring-Powell nanofluid through disposed surface area due to the existence of microorganism with inclusion the influence of non- linear thermal radiation, energy activation and bio-convection. The liquid is likely to allow conduction and thickness of the liquid is supposed to show variation exponentially. By using appropriate similarity type transforms, the nonlinear PDE's are converted into dimensionless ODE's. The results of ODE's are finally concluded by employing (HAM) Homotopy Analysis approach. The influence of relevant parameters on concentration, temperature, velocity and motile microorganism density are studied by the use of graphs and tables. We acquire skin friction, local Nusselt and motil microorganism number for various parameters.