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.

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.

Heat Transfer With a MicroPCM Suspension in Laminar Tube Flow Using a Realistic Melting Model

Volume 3 ◽  
2004 ◽  
Author(s):  
Daniel A. Cassidy ◽  
Richard D. Gould
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Numerical Solutions ◽  
Tube Wall ◽  
Heat Transfer Fluid ◽  
Uniform Heat Flux ◽  
Carrier Fluid ◽  
Single Temperature ◽  
Change Material

A microPCM fluid is a suspension of particles of microencapsulated phase-change-material (PCM) in a carrier heat transfer fluid. Such fluids have potential as pumped loop cooling media for applications in aerospace electronics cooling, terrestrial energy systems, and recently in electric vehicle cooling. The melting process of the phase change material does not occur at a single temperature but rather occurs over a temperature range. In the past, numerical solutions to microPCM fluids have assumed a linear release of latent heat over the phase change region. In this paper four analytic curve fits to differential scanning calorimeter measurements are made to better model the actual melting/solidification behavior. The numerical scheme models hydrodynamically fully developed laminar flow in a circular tube using the enthalpy method. The microPCM fluid contains 23% by weight microencapsulated octacosane particles in a 50/50% by volume ethylene glycol/water carrier fluid. A prescribed uniform heat flux at the tube wall is used. The solutions for these four cases include mixed mean exit temperature, axial tube wall temperature and local heat transfer coefficient.

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