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TECHNICAL BRIEFS

Thermal Management of Electronics in Telecommunications Products: Designing for the Network Equipment Building System (NEBS) Standards

[+] Author and Article Information
Jinny Rhee

 San Jose State University, Mechanical and Aerospace Engineering Department, One Washington Square, San Jose, CA 95192-0087jrhee@email.sjsu.edu

Sergio I. Hernandez

 Apple Computer, Product Safety Group, One Infinite Loop, Cupertino, CA 95014

J. Electron. Packag 128(4), 484-493 (Jan 09, 2006) (10 pages) doi:10.1115/1.2353327 History: Received April 01, 2005; Revised January 09, 2006

The effects of altitude, increased ambient temperature, and increased relative humidity on the board level forced convection typical of telecommunications products were systematically examined through numerical simulation and analytical techniques. Altitude was found to have the most significant impact on component temperature rise above inlet air temperature. Depending on the proportion of upstream-heating to self-heating for a given component, the component temperature rise above inlet air temperature was found to increase by 40% to 88% at 5000m when compared to the base line case at sea level. Inlet air temperature was found to translate linearly to component temperature increase. The second-order effects due to property changes with temperature were found to be less than 3% on the component temperature rise. The relative humidity was not found to significantly impact the component temperature rise at an inlet temperature of 25°C. However, the property changes at a 55°C inlet were more significant, and require further study. A temperature multiplier concept is introduced to aid practicing engineers in extrapolating data at standard conditions to the operating extremes.

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Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Photo of commercial router with board shown

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Figure 2

Theoretical representation at the board level

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Figure 3

Illustration of temperature superposition

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Figure 4

Control volume for energy balance to determine mean air temperature rise

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Figure 5

Geometry for numerical simulation

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Figure 6

Comparison of temperature profiles at two grid refinements

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Figure 7

Comparison of had from current study to experimental data in literature

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Figure 8

(a)-(f): had versus row number for various altitudes

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Figure 9

Nusselt number versus Reynolds number

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Figure 10

Multiplier for component temperature rise with altitude

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