Natural Convection in an Array of Vertical Channels with Two-Dimensional Heat Sources: Uniform and Non-Uniform Plate Heating

2004 ◽  
Vol 25 (7) ◽  
pp. 46-56 ◽  
Author(s):  
ANA CRISTINA AVELAR ◽  
MARCELO MOREIRA GANZAROLLI
Author(s):  
Tito Dias ◽  
Luiz Fernando Milanez

Laminar natural convection in a two-dimensional horizontal channel is very important in laptop design, since optimizing the utilization of the cooler saves energy from the battery. In this work, this configuration has been numerically studied. Three cases were studied according to the position of the heat sources in the lower wall, upper wall and both. The computational domain consisted of two adiabatic walls where the heat sources were positioned, and two open boundaries, where the manometric pressure and normal gradient of velocity were zero. Ambient temperature was prescribed for the entering fluid and zero normal gradient for the exiting fluid. Fluid properties were assumed constant except for the density change with temperature on the buoyancy term. The influence of the modified Rayleigh number, position of the heat sources and heat flux ratio between the sources were analyzed for Prandtl number of 0.7. The maximum temperature excess on the heat source is lower for the case with two heat sources and Ra = 104. This preliminary study showed the existence of a minimum value of the excess temperature for the studies aspect ratio (0.1).


1998 ◽  
Vol 361 ◽  
pp. 25-39 ◽  
Author(s):  
F. J. HIGUERA ◽  
P. D. WEIDMAN

An analysis is presented of some steady natural convection flows at large distances downstream of point heat sources on solid walls. These asymptotic self-similar flows depend only on the Prandtl number of the fluid. The flow induced by a localized source on an adiabatic wall that is vertical or facing downwards is described numerically, whereas the flow due to a localized source on a wall facing upwards separates and leads to a self-similar plume. When the wall is held at the same temperature as the ambient fluid far from the source, the flow is described by a self-similar solution of the second kind, with the algebraic decay of the temperature excess above the ambient temperature determined by a nonlinear eigenvalue problem. Numerical solutions of this problem are presented for two-dimensional and localized heat sources on a vertical wall, whereas the problem for a localized heat source under an inclined isothermal downwards-facing wall turns out to capture the Rayleigh–Taylor instability of the flow and could not be solved by the methods used in this paper. The analogous flows in fluid-saturated porous media are found to be the solutions of parameter-free problems. A conservation law similar to the one holding for a wall jet is found in the case of a two-dimensional source on an isothermal wall and numerical solutions are presented for the other cases.


Author(s):  
Tunc Icoz ◽  
Qinghua Wang ◽  
Yogesh Jaluria

Natural convection has important implications in many applications like cooling of electronic equipment due to its low cost and easy maintenance. In the present study, two-dimensional natural convection heat transfer to air from multiple identical protruding heat sources, which simulate electronic components, located in a horizontal channel has been studied numerically. The fluid flow and temperature profiles, above the heating elements placed between an adiabatic lower plate and an isothermal upper plate, are obtained using numerical simulation. The effects of source temperatures, channel dimensions, openings, boundary conditions, and source locations on the heat transfer from and flow above the protruding sources are investigated. Different configurations of channel dimensions and separation distances of heat sources are considered and their effects on natural convection heat transfer characteristics are studied. The results show that the channel dimensions have a significant effect on fluid flow. However, their effects on heat transfer are found to be small. The separation distance is found to be an important parameter affecting the heat transfer rate. The numerical results of temperature profiles are compared with the experimental measurements performed using Filtered Rayleigh Scattering (FRS) technique in an earlier study, indicating good agreement. It is observed that adiabatic upper plate assumption leads to better temperature predictions than isothermal plate assumption.


Author(s):  
Issam Lakkis

Vortex methods for simulating natural convection of an ideal gas in unbounded two-dimensional domains are presented. In particular, the redistribution method for diffusion is extended to enable simulation of nonlinear diffusion of an ideal gas in isobaric conditions encountered in unbounded low-Mach number flows. We also address the problem of handling source terms in grid-free vortex methods and propose a fast, accurate, and physically motivated method for solving the associated inverse problems. Examples include generation of baroclinic vorticity in non-reacting buoyancy driven flows, and in addition, generation of internal energy and species in buoyant reacting flows. Accuracy and speed of the proposed algorithms for nonlinear diffusion and vorticity generation are investigated separately. Simulations of natural convection of a “thermal patch” for Grashof number ranging from to 1562.5 to 25000 are presented.


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