Forced Convective Cooling Enhancement of Electronic Package Configurations Through Self-Sustained Oscillatory Flows

1993 ◽  
Vol 115 (4) ◽  
pp. 356-365 ◽  
Author(s):  
J. S. Nigen ◽  
C. H. Amon
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Printed Circuit Board ◽  
Local Heat Transfer ◽  
Thermal Design ◽  
Circuit Board ◽  
Electronic Packages ◽  
Transfer Coefficients ◽  
Electronic Package ◽  
Heat Transfer Coefficients

Two-dimensional arrangements of electronic packages surface mounted to a printed circuit board represent grooved-channel geometries. For a certain range of Reynolds numbers, these geometries excite and sustain instabilities that are normally damped in planar Poiseuille flows. This results in a bifurcation to a self-sustained oscillatory state, which improves mixing and thereby enhances convective heat transport. Numerical simulations of the flow field and heat transfer characteristics of oscillatory and nonoscillatory flows for five grooved channels are presented. Additionally, the numerically obtained flow field corresponding to a suspended electronic package is analyzed. The extent of heat transfer enhancement is gauged through direct comparison to results corresponding to the steady-flow regime. Local heat transfer coefficients are determined and used to calculate the temperature distribution within a surface-mounted package. Moreover, the importance of using locally-defined instead of spatially-averaged heat transfer coefficients for thermal design and analysis of electronic packages is discussed.

scholarly journals Modelling of temperature distribution along PCB thickness in different substrates during reflow

Circuit World ◽  
2019 ◽  
Vol 46 (2) ◽  
pp. 85-92
Author(s):  
Daniel Straubinger ◽  
István Bozsóki ◽  
David Bušek ◽  
Balázs Illés ◽  
Attila Géczy
Keyword(s):  
Heat Transfer ◽  
Printed Circuit Board ◽  
Vapour Phase ◽  
Circuit Board ◽  
Transfer Coefficients ◽  
Content Type ◽  
Printed Circuit ◽  
Heat Transfer Coefficients ◽  
Significant Temperature ◽  
The Difference

Purpose In this paper, analytical modelling of heat distribution along the thickness of different printed circuit board (PCB) substrates is presented according to the 1 D heat transient conduction problem. This paper aims to reveal differences between the substrates and the geometry configurations and elaborate on further application of explicit modelling. Design/methodology/approach Different substrates were considered: classic FR4 and polyimide, ceramics (BeO, Al2O3) and novel biodegradables (polylactic-acid [PLA] and cellulose acetate [CA]). The board thicknesses were given in 0.25 mm steps. Results are calculated for heat transfer coefficients of convection and vapour phase (condensation) soldering. Even heat transfer is assumed on both PCB sides. Findings It was found that temperature distributions along PCB thicknesses are mostly negligible from solder joint formation aspects, and most of the materials can be used in explicit reflow profile modelling. However PLA shows significant temperature differences, pointing to possible modelling imprecisions. It was also shown, that while the difference between midplane and surface temperatures mainly depend on thermal diffusivity, the time to reach solder alloy melting point on the surface depends on volumetric heat capacity. Originality/value Results validate the applicability of explicit heat transfer modelling of PCBs during reflow for different heat transfer methods. The results can be incorporated into more complex simulations and profile predicting algorithms for industrial ovens controlled in the wake of Industry 4.0 directives for better temperature control and ultimately higher soldering quality.

An Experimental Investigation of a Staggered Array of Heatsinks in the Hydrodynamic and Thermal Entrance Regions of a Duct

1993 ◽  
Vol 115 (1) ◽  
pp. 106-111 ◽  
Author(s):  
Sarah M. Bazydola ◽  
Mohammad E. Taslim
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Electronic Packages ◽  
Computer Design ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Engineering Costs ◽  
Thermal Entrance

The need for methods to predict temperatures of electronic packages is becoming more important as time to market decreases and the need to reduce engineering costs increases. Geometric parameters that are commonly found in a card cage computer design are duct height to package height ratio (H/B) and longitudinal to latitudinal spacing (L/D). The velocity of the air flowing through the card cage is also an important parameter. The purpose of this experimental research is to develop correlations that can be used to predict heat transfer coefficients and thus temperatures of electronic packages in a staggered array in the hydrodynamic and thermal entrance regions of a duct. The ten components in the array are mounted on one wall of the duct to simulate a printed circuit board in a card cage. Results are presented for three values of Reynolds number (20250, 50000 and 65000) for a range of H/B from 1 to 5 by increments of 2 while L/D is varied from 1 to 3 by increments of 0.5. Comparisons are made between upstream and downstream packages. It was determined that one correlation could be used to predict the Nusselt number for upstream heatsinks. This correlation is a function of Reynolds number and H/B. The results also indicate that three correlations are necessary to predict the Nusselt number of downstream heatsinks. When H/B = 1, the Nusselt number is only a function of Reynolds number; when H/B is greater than 1 and L/D is less than 2, the Nusselt number is dependent on Reynolds number, H/B and L/D; when H/B is greater than 1 and L/D is greater than or equal to 2, the Nusselt number is a function of Reynolds number and H/B.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

scholarly journals Heat Transfer Coefficient Determination in a Gravity Die Casting Process with Local Air Gap Formation and Contact Pressure Using Experimental Evaluation and Numerical Simulation

2021 ◽  
Author(s):  
T. Vossel ◽  
N. Wolff ◽  
B. Pustal ◽  
A. Bührig-Polaczek ◽  
M. Ahmadein
Keyword(s):  
Heat Transfer ◽  
Contact Pressure ◽  
Local Heat Transfer ◽  
Casting Process ◽  
Local Heat ◽  
Air Gap ◽  
Gap Formation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Die Casting Process

AbstractAnticipating the processes and parameters involved for accomplishing a sound metal casting requires an in-depth understanding of the underlying behaviors characterizing a liquid melt solidifying inside its mold. Heat balance represents a major factor in describing the thermal conditions in a casting process and one of its main influences is the heat transfer between the casting and its surroundings. Local heat transfer coefficients describe how well heat can be transferred from one body or material to another. This paper will discuss the estimation of these coefficients in a gravity die casting process with local air gap formation and heat shrinkage induced contact pressure. Both an experimental evaluation and a numerical modeling for a solidification simulation will be performed as two means of investigating the local heat transfer coefficients and their local differences for regions with air gap formation or contact pressure when casting A356 (AlSi7Mg0.3).

scholarly journals Condensation inside smooth horizontal tubes: Part 1. Survey of the methods of heat-exchange prediction

2015 ◽  
Vol 19 (5) ◽  
pp. 1769-1789 ◽  
Author(s):  
Volodymyr Rifert ◽  
Volodymyr Sereda
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Film Condensation ◽  
Experimental Investigations ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

Survey of the works on condensation inside smooth horizontal tubes published from 1955 to 2013 has been performed. Theoretical and experimental investigations, as well as more than 25 methods and correlations for heat transfer prediction are considered. It is shown that accuracy of this prediction depends on the accuracy of volumetric vapor content and pressure drop at the interphase. The necessity of new studies concerning both local heat transfer coefficients and film condensation along tube perimeter and length under annular, stratified and intermediate regimes of phase flow was substantiated. These characteristics being defined will allow determining more precisely the boundaries of the flow regimes and the methods of heat transfer prediction.

Heat Transfer and Pressure Drop Correlations for Square Channels With 45 Deg Ribs at High Reynolds Numbers

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Huitao Yang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Cooling Passage

Systematic experiments are conducted to measure heat transfer enhancement and pressure loss characteristics on a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 45 deg parallel ribs. Copper plates fitted with a silicone heater and instrumented with thermocouples are used to measure regionally averaged local heat transfer coefficients. Reynolds numbers studied in the channel range from 30,000 to 400,000. The rib height (e) to hydraulic diameter (D) ratio ranges from 0.1 to 0.18. The rib spacing (p) to height ratio (p/e) ranges from 5 to 10. Results show higher heat transfer coefficients at smaller values of p/e and larger values of e/D, though at the cost of higher friction losses. Results also indicate that the thermal performance of the ribbed channel falls with increasing Reynolds numbers. Correlations predicting Nusselt number (Nu) and friction factor (f¯) as a function of p/e, e/D, and Re are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+), p/e, and e/D.

Experimental Investigation of Local Heat Transfer Distribution on Smooth and Roughened Surfaces Under an Array of Angled Impinging Jets

2001 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Deborah A. Kaminski
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Roughened Surface

Abstract Measurements of the local heat transfer distribution on smooth and roughened surfaces under an array of angled impinging jets are presented. The test rig is designed to simulate impingement with cross-flow in one direction which is a common method for cooling gas turbine components such as the combustion liner. Jet angle is varied between 30, 60, and 90 degrees as measured from the impingement surface, which is either smooth or randomly roughened. Liquid crystal video thermography is used to capture surface temperature data at five different jet Reynolds numbers ranging between 15,000 and 35,000. The effect of jet angle, Reynolds number, gap, and surface roughness on heat transfer efficiency and pressure loss is determined along with the various interactions among these parameters. Peak heat transfer coefficients for the range of Reynolds number from 15,000 to 35,000 are highest for orthogonal jets impinging on roughened surface; peak Nu values for this configuration ranged from 88 to 165 depending on Reynolds number. The ratio of peak to average Nu is lowest for 30-degree jets impinging on roughened surfaces. It is often desirable to minimize this ratio in order to decrease thermal gradients, which could lead to thermal fatigue. High thermal stress can significantly reduce the useful life of engineering components and machinery. Peak heat transfer coefficients decay in the cross-flow direction by close to 24% over a dimensionless length of 20. The decrease of spanwise average Nu in the crossflow direction is lowest for the case of 30-degree jets impinging on a roughened surface where the decrease was less than 3%. The decrease is greatest for 30-degree jet impingement on a smooth surface where the stagnation point Nu decreased by more than 23% for some Reynolds numbers.

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