Optimization of Parallel, Horizontal, and Laminar Forced Air-Cooled Heat Generating Boards

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
M. O. Özdemir ◽  
H. Yüncü
Keyword(s):  
Forced Convection ◽  
Heat Dissipation ◽  
Rectangular Channel ◽  
Numerical Procedure ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Constant Property ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Optimal Spacing

The objective of this study is to predict numerically the optimal spacing between parallel heat generating boards. The isothermal boards are stacked in a fixed volume of electronic package enclosed by insulated lateral walls, and they are cooled by laminar forced convection of air with prescribed pressure drop. In the numerical procedure, governing equations for the solution of forced convection of constant property incompressible flow through one rectangular channel are solved. Resulting flow and temperature fields in each rectangular channel yield the optimal board-to-board spacing by which maximum heat dissipation rate from the package to the air is achieved. Next, generalized correlations for the determination of the maximum heat transfer rate from the package and optimal spacing between boards are derived in terms of prescribed pressure difference, board length, and density and kinematic viscosity of air. Finally, corresponding correlations are compared with the available two-dimensional studies in literature for infinite parallel plates.

On Combined Free and Forced Convection in Channels

1960 ◽  
Vol 82 (3) ◽  
pp. 233-238 ◽  
Author(s):  
L. N. Tao
Keyword(s):  
Forced Convection ◽  
Rectangular Channel ◽  
Complex Function ◽  
Vertical Channel ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Free And Forced Convection ◽  
Energy Equations ◽  
Helmholtz Wave Equation ◽  
Transfer Problems

The heat-transfer problems of combined free and forced convection by a fully developed laminar flow in a vertical channel of constant axial wall temperature gradient with or without heat generations are approached by a new method. By introducing a complex function which is directly related to the velocity and temperature fields, the coupled momentum and energy equations are readily combinable to a Helmholtz wave equation in the complex domain. This greatly reduces the complexities of the problems. For illustrations, the cases of flows between parallel plates and in a rectangular channel are treated. It shows that this method is more direct and powerful than those of previous investigations.

scholarly journals Maximum Heat Transfer Rate Density in Two-Dimensional Minichannels and Microchannels

2003 ◽  
Author(s):  
M. Favre-Marinet ◽  
S. Le Person ◽  
A. Bejan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Transition To Turbulence ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Parallel Plates ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Optimal Spacing

Experimental investigations of the flow and the associated heat transfer were conducted in two-dimensional microchannels in order to test possible size effects on the laws of hydrodynamics and heat transfer and to infer optimal conditions of use from the measurements. The test section was designed to modify easily the channel height e between 1 mm and 0.1 mm. Measurements of the overall friction factor and local Nusselt numbers show that the classical laws of hydrodynamics and heat transfer are verified for e > 0.4 mm. For lower values of e, a significant decrease of the Nusselt number is observed, whereas the Poiseuille number continues to have the conventional value of laminar developed flow. The transition to turbulence is not affected by the channel size. For fixed pressure drop across the channel, a maximum of heat transfer rate density is found for a particular value of e. The corresponding dimensionless optimal spacing and heat transfer rate density are in very good agreement with the predictions of Bejan and Sciubba (1992). This paper is the first time that the optimal spacing between parallel plates is determined experimentally.

Forced Convection in a Uniformly Heated Enclosure: Effect of the Inlet and Two Outlet Port Locations

2007 ◽  
Author(s):  
A. I. Botello-Arredondo ◽  
A. Hernandez-Guerrero ◽  
C. Rubio-Arana ◽  
M. Picon-Nun˜ez
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Temperature Fields ◽  
Transfer Enhancement ◽  
Square Cavity ◽  
Maximum Heat ◽  
Number Range ◽  
Outlet Port ◽  
Maximum Heat Transfer ◽  
Effective Design

In an earlier study, Saeidi and Khodadadi presented results on forced convection inside a square cavity with one inlet and one outlet ports. Their most effective design showed maximum heat transfer and minimum pressure drop for a particular location of the ports. In the present study a cavity with one inlet and two outlet ports is considered, and different conditions and geometric arrays for the position of the ports are analyzed. The cold incoming fluid is heated by the isothermal hot walls. The outlet ports are positioned at forty-five different locations on the walls. A Reynolds number range of 10 < Re < 500 is considered, clearly within the laminar regimen. The flow and temperature fields are obtained as part of the solution. As expected, an increment of vorticity brought a heat transfer enhancement. The effect of the outlet ports and their location is discussed.

Numerical Prediction of Flow and Heat Transfer in a Parallel Plate Channel With Staggered Fins

1987 ◽  
Vol 109 (1) ◽  
pp. 25-30 ◽  
Author(s):  
K. M. Kelkar ◽  
S. V. Patankar
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Periodic Variation ◽  
Local Heat ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Constant Property ◽  
Cross Sectional ◽  
Flow And Heat Transfer ◽  
Order Of Magnitude

Fluid flow and heat transfer in two-dimensional finned passages were analyzed for constant property laminar flow. The passage is formed by two parallel plates to which fins are attached in a staggered fashion. Both the plates are maintained at a constant temperature. Streamwise periodic variation of the cross-sectional area causes the flow and temperature fields to repeat periodically after a certain developing length. Computations were performed for different values of the Reynolds number, the Prandtl number, geometric parameters, and the fin-conductance parameter. The fins were found to cause the flow to deflect significantly and impinge upon the opposite wall so as to increase the heat transfer significantly. However, the associated increase in pressure drop was an order of magnitude higher than the increase in heat transfer. Streamline patterns and local heat transfer results are presented in addition to the overall results.

Buoyancy Effects in the Entrance Region of an Inclined Multirectangular-Channel Solar Collector

1983 ◽  
Vol 105 (2) ◽  
pp. 157-162 ◽  
Author(s):  
S. M. Morcos ◽  
M. M. M. Abou-Ellail
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Solar Collector ◽  
Flux Distribution ◽  
Rectangular Channel ◽  
Numerical Procedure ◽  
Side Wall ◽  
Entrance Region ◽  
Heat Flux Distribution ◽  
Constant Property

A numerical procedure is presented for the entrance region of an inclined multirectangular-channel solar collector with significant buoyancy effects. The upper wall heat flux is taken to be uniform, while the lower wall is assumed to be insulated. The heat flux distribution on the side wall of the rectangular channel is obtained by coupling a heat-conduction numerical procedure in the metallic region surrounding the channel to the main numerical procedure which solves the hydrodynamic and energy equations of the flow inside the channel. Numerical results are presented for water flowing in a multirectangular-channel solar collector with an aspect ratio AR = 4 inclined at an angle α = 30 deg to the horizontal. The resulting variable heat flux distribution on the side wall enhances the intensity of the secondary flow. The effects of the nonuniform heat flux distribution and the spacing between the rectangular channels on the variation of Nusselt number in the entrance region are presented for different values of Rayleigh number. At a value of Ra = 5 × 105, Nusselt number is more than 300 percent above the constant property prediction.

Unsteady Laminar Pulsating Flow in a Saturated Porous Microchannel in the Presence of Electrical Double-Layer Effects

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Muhammad Dilawar Khan Niazi ◽  
Hang Xu
Keyword(s):  
Angular Velocity ◽  
Forced Convection ◽  
Double Layer ◽  
Analytical Solutions ◽  
Electrical Double Layer ◽  
Darcy Number ◽  
Pulsating Flow ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Periodic Pressure

Abstract The forced convection of a pulsating flow in a saturated porous parallel-plates microchannel driven by a periodic pressure in the presence of an electrical double layer is investigated. Such configuration is very important but seldom considered in literature. Analytical solutions for electrical, momentum, and temperature fields are obtained by means of a substitution approach. The results show that the flow fields depend highly on the electro-osmotic parameter κ, the angular velocity parameter Ω, as well as the Darcy number Da.

Numerical Prediction of Fluid Flow and Heat Transfer in the Target System of an Axisymmetric Accelerator-Driven Subcritical System

2006 ◽  
Vol 129 (4) ◽  
pp. 582-588 ◽  
Author(s):  
K. Arul Prakash ◽  
G. Biswas ◽  
B. V. Rathish Kumar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Thermal Conditions ◽  
Temperature Fields ◽  
Target System ◽  
Fe Method ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Target Module ◽  
Subcritical System

Thermal hydraulics related to the design of the spallation target module of an accelerator-driven subcritical system (ADSS) was investigated numerically using a streamline upwind Petrov-Galerkin (SUPG) finite element (FE) method. A large amount of heat is deposited on the window and in the target during the course of nuclear reaction between the proton beam and the molten lead-bismuth eutectic (LBE) target. Simulations were carried out to predict the characteristics of the flow and temperature fields in the target module with a funnel-shaped flow guide and spherical bottom of the container. The beam window was kept under various thermal conditions. The analysis was extended to the case of heat generation in the LBE. The principal purpose of the analysis was to trace the temperature distribution on the beam window and in the LBE. In the case of turbulent flows, the number of recirculation regions is decreased and the maximum heat transfer was found to take place downstream of the stagnation zone on the window.

scholarly journals Heat Transfer between an Individual Carbon Nanotube and Gas Environment in a Wide Knudsen Number Regime

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Hai-Dong Wang ◽  
Jin-Hui Liu ◽  
Xing Zhang ◽  
Tian-Yi Li ◽  
Ru-Fan Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Carbon Nanotube ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Critical Diameter ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Efficient Prediction ◽  
Gas Environment

Applications of carbon nanotube (CNT) and graphene in thermal management have recently attracted significant attention. However, the lack of efficient prediction formula for heat transfer coefficient between nanomaterials and gas environment limits the further development of this technique. In this work, a kinetic model has been established to predict the heat transfer coefficient of an individual CNT in gas environment. The heat dissipation around the CNT is governed by molecular collisions, and outside the collision layer, the heat conduction is dominant. At nanoscales, the natural convection can be neglected. In order to describe the intermolecular collisions around the CNT quantitatively, a correction factor 1/24 is introduced and agrees well with the experimental observation. The prediction of the present model is in good agreement with our experimental results in free molecular regime. Further, a maximum heat transfer coefficient occurs at a critical diameter of several nanometers, providing guidelines on the practical design of CNT-based heat spreaders.

Constructal Design of Forced Convection Cooled Microchannel Heat Sinks and Heat Exchangers

2005 ◽  
Author(s):  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Parallel Plate ◽  
Rectangular Channel ◽  
Bejan Number ◽  
Square Duct ◽  
Maximum Heat ◽  
Circular Duct ◽  
Maximum Heat Transfer ◽  
Efficient Packing ◽  
Plate Channel

Heat transfer from arrays of circular and non-circular ducts subject to finite volume and constant pressure drop constraints is examined. It is shown that the optimal duct dimension is independent of the array structure and hence represents an optimal construction element. Solutions are presented for the optimal duct dimensions and maximum heat transfer per unit volume for the parallel plate channel, rectangular channel, elliptic duct, circular duct, polygonal ducts, and triangular ducts. Approximate analytical results show that the optimal shape is the isosceles right triangle and square duct due to their ability to provide the most efficient packing in a fixed volume. Whereas a more exact analysis reveals that the parallel plate channel array is in fact the superior system. An approximate relationship is developed which is very nearly a universal solution for any duct shape in terms of the Bejan number and duct aspect ratio. Finally, validation of the relationships is provided using exact results from the open literature.

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