An experimental study on the performance of miniature heat sinks for forced convection air cooling

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

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Improving the Thermal Performance of a Forced Convection Air Cooled Solution: Part 1 — Modification of Heat Sink Assembly

Volume 2: Thermal Management; Data Centers and Energy Efficient Electronic Systems ◽

10.1115/ipack2013-73108 ◽

2013 ◽

Author(s):

Saeed Ghalambor ◽

John Edward Fernandes ◽

Dereje Agonafer ◽

Veerendra Mulay

Keyword(s):

Pressure Distribution ◽

Forced Convection ◽

Thermal Performance ◽

Heat Sink ◽

Heat Sinks ◽

Thermal Interface Material ◽

Air Cooling ◽

Interfacial Pressure ◽

Interfacial Contact ◽

Torque Analysis

Forced convection air cooling using heat sinks is one of the most prevalent methods in thermal management of microelectronic devices. Improving the performance of such a solution may involve minimizing the external thermal resistance (Rext) of the package. For a given heat sink design, this can be achieved by reducing the thermal interface material (TIM) thickness through promotion of a uniform interfacial pressure distribution between the device and heat sink. In this study, a dual-CPU rackmount server is considered and modifications to the heat sink assembly such as backplate thickness and bolting configuration are investigated to achieve the aforementioned improvements. A full-scale, simplified model of the motherboard is deployed in ANSYS Mechanical, with emphasis on non-linear contact analysis and torque analysis of spring screws, to determine the optimal design of the heat sink assembly. It is observed that improved interfacial contact and pressure distribution is achieved by increasing the number of screws (loading points) and positioning them as close to the contact area as possible. The numerical model is validated by comparison with experimental measurements within reasonable accuracy. Based on the results of numerical analysis, the heat sink assembly is modified and improvement over the base configuration is experimentally quantified through interfacial pressure measurement. The effect of improved interfacial contact on thermal performance of the solution is discussed.

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Experimental Study of Forced Convection Through Microporous Enhanced Heat Sinks

Emerging Technologies and Techniques in Porous Media ◽

10.1007/978-94-007-0971-3_28 ◽

2004 ◽

pp. 433-452 ◽

Cited By ~ 3

Author(s):

J. L. Lage ◽

A. Narasimhan ◽

D. C. Porneala ◽

D. C. Price

Keyword(s):

Experimental Study ◽

Forced Convection ◽

Heat Sinks

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Forced Convection Air Cooling of Simulated Low Profile Electronic Components: Part 2—Heat Sink Effects

Journal of Electronic Packaging ◽

10.1115/1.2905363 ◽

1991 ◽

Vol 113 (1) ◽

pp. 27-32 ◽

Cited By ~ 2

Author(s):

G. L. Lehmann ◽

J. Pembroke

Keyword(s):

Heat Transfer ◽

Forced Convection ◽

Flow Rate ◽

Heat Sink ◽

Heat Sinks ◽

Air Cooling ◽

Channel Spacing ◽

Heat Transfer Behavior ◽

Low Profile ◽

Transfer Behavior

Forced convection air cooling of an array of low profile, card-mounted components has been investigated. A simulated array is attached to one wall of a low aspect ratio duct. This is the second half of a two-part study. In this second part the presence of a longitudinally finned heat sink is considered. The heat sink is a thermally passive “flow disturbance”. Laboratory measurements of the heat transfer rates downstream of the heat sink are reported and compared with the measured values which occur when no heat sinks are present. Data are presented for three heat sink geometries subject to variations in channel spacing and flow rate. In the flow range considered laminar, transitional and turbulent heat transfer behavior has been observed. The presence of a heat sink appears to “trip” the start of transition at lower Reynolds numbers than when no heat sinks are present. A Reynolds number based on component length provides a good correlation of the heat transfer behavior due to variations in flow rate and channel spacing. Heat transfer is most strongly effected by flow rate and position relative to the heat sink. Depending on the flow regime (laminar or turbulent) both relative enhancement and reductions in the component Nusselt number have been observed. The impact of introducing a heat sink is greatest for flow rates corresponding to transitional behavior.

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Effect of Flow Bypass on the Performance of Longitudinal Fin Heat Sinks

Journal of Electronic Packaging ◽

10.1115/1.2905687 ◽

1994 ◽

Vol 116 (3) ◽

pp. 206-211 ◽

Cited By ~ 63

Author(s):

R. A. Wirtz ◽

Weiming Chen ◽

Ronghua Zhou

Keyword(s):

Heat Transfer ◽

Forced Convection ◽

Thermal Performance ◽

Heat Sink ◽

Design Guidelines ◽

Heat Sinks ◽

Air Cooling ◽

Regular Array ◽

Electronic Package ◽

And Performance

Heat transfer experiments are reported on the thermal performance of longitudinal fin heat sinks attached to an electronic package which is part of a regular array of packages undergoing forced convection air cooling. The effect of coolant bypass on the performance of the heat sink is assessed and performance correlations for reduced heat transfer due to this effect are developed. These correlations are used to develop design guidelines for optimal performance.

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An Experimental Study on the Design of Miniature Heat Sinks for Forced Convection Air Cooling

Journal of Heat Transfer ◽

10.1115/1.3110005 ◽

2009 ◽

Vol 131 (7) ◽

Cited By ~ 29

Author(s):

Vanessa Egan ◽

Jason Stafford ◽

Pat Walsh ◽

Ed Walsh

Keyword(s):

Experimental Study ◽

Heat Sinks ◽

Cooling Power ◽

Air Cooling ◽

Pressure Losses ◽

Low Profile ◽

Image Velocimetry ◽

Profile Height ◽

Footprint Area ◽

Heat Sink Design

An experimental study is performed on one of the smallest commercially available miniature fans, suitable for cooling portable electronic devices, used in conjunction with both finned and finless heat sinks of equal exterior dimensions. The maximum overall footprint area of the cooling solution is 534mm2 with a profile height of 5 mm. Previous analysis has shown that due to fan exit angle, flow does not enter the heat sinks parallel to the fins or bounding walls. This results in a nonuniform flow rate within the channels of the finned and finless heat sinks along with impingement of the flow at the entrance giving rise to large entrance pressure losses. In this paper straightening diffusers were attached at the exit of the fan, which resulted in aligning the flow entering the heat sinks with the fins and channel walls. Detailed velocity measurements were obtained using particle image velocimetry, which provided a further insight into the physics of the flow in such miniature geometries and in designing the straightening diffusers. The thermal analysis results indicate that the cooling power of the solution is increased by up to 20% through the introduction of a diffuser, hence demonstrating the need for integrated fan and heat sink design of low profile applications.

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Active Upstream Components for Enhanced Heat Transfer of Longitudinally Finned Heat Sinks

2010 14th International Heat Transfer Conference, Volume 3 ◽

10.1115/ihtc14-22203 ◽

2010 ◽

Author(s):

John Daly

Keyword(s):

Heat Transfer ◽

Forced Convection ◽

Heat Sink ◽

Performance Enhancement ◽

Heat Sinks ◽

Air Cooling ◽

Active Components ◽

Enhanced Heat Transfer ◽

Current Standard ◽

Piezoelectric Fans

With the ever increasing heat flux from next-generation chips forced convection cooling is beginning to reach its limits within current standard heat sink capabilities. Methods of extending the air cooling capabilities prior to a transition to liquid or refrigerant-based cooling which is seen as costly and complex, have become more critical. This paper investigates the enhanced heat transfer by the addition of active components upstream of a longitudinally finned heat sink. This paper addresses piezoelectric fans for natural and forced convection environments. Experimental measurements are taken for a low powered DC fan operating at a frequency of 114Hz. For the forced convection experiments a fully ducted flow was used. The main thrust of the paper is to determine the effects of piezoelectrics in augmenting forced convection systems at hot component locations. The effects on pressure drop, thermal resistance and pumping power with the addition of the technology are presented. The paper concludes by reporting on the performance enhancement and limitations of the piezoelectric fans compared to the conventional longitudinally finned heat sink geometry.

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