Enhanced Passive Thermal Management of Grid-Scale Power Routers Utilizing Ionic Wind

2014 ◽  
Author(s):  
Noris Gallandat ◽  
J. Rhett Mayor
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Mixed Boundary ◽  
Control Volume ◽  
Vertical Channel ◽  
Mixed Boundary Conditions ◽  
Thermal Design ◽  
Finite Difference Approximation ◽  
Difference Approximation ◽  
Ionic Wind

This paper presents a numerical model assessing the potential of ionic wind as a heat transfer enhancement method for the cooling of grid distribution assets. Distribution scale power routers (13–37 kV, 1–10 MW) have stringent requirements regarding lifetime and reliability, so that any cooling technique involving moving parts such as fans or pumps are not viable. Increasing the air flow — and thereby enhancing heat transfer — through Corona discharge could be an attractive solution to the thermal design of such devices. In this work, the geometry of a rectangular, vertical channel with a corona electrode at the entrance is considered. The multiphysics problem is characterized by a set of four differential equations: the Poisson equation for the electric field and conservation equations for electric charges, momentum and energy. The electrodynamics part of the problem is solved using a finite difference approximation (FDA). Solutions for the potential, electric field and free charge density are presented for a rectangular control volume with mixed boundary conditions.

scholarly journals Benchmark Studies for the Generalized Streamwise Periodic Heat Transfer Problem

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Steven B. Beale
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Transfer Problem ◽  
Mixed Boundary ◽  
Mixed Boundary Conditions ◽  
Wall Boundary Conditions ◽  
Engineering Problems ◽  
Complex Engineering ◽  
The Common ◽  
Periodic Heat

This is a comparison of calculations performed with a scheme for handling streamwise-periodic boundary conditions with known solutions to the common problem of fully developed heat transfer in a plane duct. Constant value, constant flux, mixed boundary conditions, and linear wall flux (conjugate heat transfer) are all considered. Agreement is, in every case, near exact showing that the methodology may be applied with confidence to complex engineering problems with a variety of thermal wall boundary conditions.

scholarly journals Diffusion-drift model of ion migration over interstitial sites of a two-dimensional lattice

2019 ◽  
Vol 55 (3) ◽  
pp. 355-365
Author(s):  
N. A. Poklonski ◽  
A. O. Bury ◽  
N. G. Abrashina-Zhadaeva ◽  
S. A. Vyrko
Keyword(s):  
Electric Field ◽  
Ion Current ◽  
Finite Difference Approximation ◽  
Square Lattice ◽  
Difference Approximation ◽  
Water Molecules ◽  
Ion Migration ◽  
Drift Model ◽  
Stationary Electric Field ◽  
Electric Potentials

An analytical and numerical modeling of the process of obtaining hydroxyl radicals OH0 and atomic hydrogen H0 from water molecules on a square lattice based on electrical neutralization of ions OH− on an anode and ions H+ on a cathode is conducted. The numerical solution of a system of equations describing a stationary migration of ions H+ and OH− over the interstitial sites of a square lattice located in an external electric field is considered. The ions H+ and OH− in the interstitial sites of a square lattice are generated as a result of dissociation of a water molecule under the action of external electromagnetic radiation and external constant (stationary) electric field. It is assumed that anode and cathode are unlimited ion sinks. The problem is solved using the finite difference approximation for the initial system of differential equations with the construction of an iterative process due to the nonlinearity of the constituent equations. It is shown by using calculation that the dependence of the ion current on a difference of electric potentials between anode and cathode is sublinear.

scholarly journals Transient Formulations for a Heat-Generating Fin with a Temperature-Dependent Heat Transfer Coefficient and Thermal Conductivity

2019 ◽  
Vol 2 (2) ◽  
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Governing Equation ◽  
Neumann Boundary ◽  
Finite Difference Approximation ◽  
Difference Approximation ◽  
Temperature Dependent ◽  
Discrete Equations ◽  
Highly Nonlinear ◽  
Temporal Derivative

Numerical calculations and scalar transport analyses are carried out for transient heat transfer in a heat generating fin with a temperature-dependent heat transfer and conduction coefficients. The highly nonlinear governing equation, satisfies the Dirichlet and Neumann boundary conditions at both ends of the problem domain.Integral representation of the governing equation over the discretized problem domain is achieved via the Green’s second identity together with the so called free- space Green function . This element-driven approach togetherwith the finite difference approximation of the temporal derivative result in discrete equations which are recursive in nature. At the boundaries of any of the adjacent elements, compatibility conditions and/or boundary conditions are enforced to guarantee scalar continuity. After the resulting system of discrete equations are numerically solved and assembled, they yield the transient history of the scalar variables at any particular point in time. Several numerical tests are carried out to ensure the convergence and accuracy of the formulation by comparing numerical results with those found in literature.

Numerical Simulation for Thermal Design of a Gas Water Heater With Turbulent Combined Convection

2015 ◽  
Author(s):  
Ali Yari ◽  
Siamak Hosseinzadeh ◽  
Ali Akbar Golneshan ◽  
Ramin Ghasemiasl
Keyword(s):  
Heat Transfer ◽  
Control Volume ◽  
Geometric Parameters ◽  
Thermal Design ◽  
Navier Stokes ◽  
Total Efficiency ◽  
Water Heater ◽  
Hydrodynamic Behaviour ◽  
Turbulent Models ◽  
Energy Equations

This article investigates the effects of geometric parameters on a turbulent asymmetrical heat transfer in vertical channels with radiation and blowing from a wall. Hydrodynamic behaviour and heat transfer results are obtained by the solution of the complete Navier–Stokes and energy equations using a control volume finite element method. In this paper, commercial codes were used to solve the equations. The equations involved were numerically solved with three turbulent models including Spalart-Allmaras, R-N-G k-ε with ‘standard wall function’ wall nearby model, R-N-G k-ε with ‘enhanced wall treatment’ wall nearby model and ‘ray tracing’ radiation techniques. Turbulent flow with ‘low Reynolds Spalart-Allmaras turbulence model’ and radiation with ‘discrete transfer radiation method’ was modelled. The results were compared with experimental data and appropriate methods were selected for turbulent modelling. The problems of different Grashof number, Reynolds number, radiation parameters and Prandtl number were solved and the effects of geometric parameters on the fluid flow, radiation-convection-blowing heat transfer and the total efficiency were determined.

Natural Convection in a Corrugated Enclosure With Mixed Boundary Conditions

1996 ◽  
Vol 118 (1) ◽  
pp. 50-57 ◽  
Author(s):  
S. Noorshahi ◽  
C. A. Hall ◽  
E. K. Glakpe
Keyword(s):  
Heat Transfer ◽  
Coordinate System ◽  
Numerical Solutions ◽  
Amplitude Ratio ◽  
Mixed Boundary ◽  
Unit Length ◽  
Mixed Boundary Conditions ◽  
Uniform Heat Flux ◽  
Corrugated Surface ◽  
Inclination Angles

Numerical solutions to the two-dimensional equations governing natural convective flow of air (Prandtl number = 0.71) contained in an enclosure with varying angles of inclination to the horizontal axis have been obtained. The air layer is bounded by a corrugated surface under uniform heat flux conditions, a flat isothermal cooled surface and around the edges by flat adiabatic surfaces. The numerical solutions are obtained in a transformed coordinate system in which the boundaries of the enclosure coincide with coordinate surfaces. The coordinate system is generated with simple algebraic expressions. The numerical scheme is employed in performing parametric heat transfer calculations. The range of parameters investigated include: modified Rayleigh numbers up to 106, amplitude aspect ratio from 0 to 0.4, inclination angles of 30, 60, and 90 degrees, and number of cycles per unit length of enclosure values of 4/5 and 4. All parameters investigated have varying degrees of influence on the heat transfer and fluid flow. In addition to the usual influence of the modified Rayleigh number on natural convective flows, the region of pseudo-conduction is increased as the enclosure amplitude ratio is increased. The distributions of temperature along the corrugated surface suggest that correlations obtained under isothermal conditions cannot be employed in the design or analysis of the energy transfer system investigated.

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