Thermal Computations for Electronics

Conductive, Radiative, and Convective Air Cooling, 1st Edition

CRC Press

416 pages | 251 B/W Illus.

Hardback: 9781439850176
pub: 2010-11-08
SAVE ~\$31.00
\$155.00
\$124.00
x
eBook (VitalSource) : 9780429111945
pub: 2010-11-08
from \$77.50

FREE Standard Shipping!

Description

A total revision of the author’s previous work, Thermal Computations for Electronics: Conductive, Radiative, and Convective Air Cooling is a versatile reference that was carefully designed to help readers master mathematical calculation, prediction, and application methods for conductive, radiative, and convective heat transfer in electronic equipment. Presenting material in a way that is practical and useful to engineers and scientists, as well as engineering students, this book provides very detailed text examples and their solutions. This approach helps users at all levels of comprehension to strengthen their grasp of the subject and detect their own calculation errors.

The beginning of this book is largely devoted to prediction of airflow and well-mixed air temperatures in systems and heat sinks, after which it explores convective heat transfer from heat sinks, circuit boards, and components. Applying a systematic presentation of information to enhance understanding and computational practice, this book:

• Provides complete mathematical derivations and supplements formulae with design plots
• Offers complete exercise solutions (Mathcad™ worksheets and PDF images of Mathcad worksheets), lecture aids (landscape-formatted PDF files), and text-example Mathcad worksheets for professors adopting this book
• Addresses topics such as methods for multi-surface radiation exchange, conductive heat transfer in electronics, and finite element theory with a variational calculus method explained for heat conduction
• Presents mathematical descriptions of large thermal network problem formulation
• Discusses comprehensive thermal spreading resistance theory, and includes steady-state and time-dependent problems

This reference is useful as a professional resource and also ideal for use in a complete course on the subject of electronics cooling, with its suggested course schedule and other helpful advice for instructors. Selected sections may be used as application examples in a traditional heat transfer course or to help professionals improve practical computational applications.

Reviews

The material is presented in a practical way, very suitable for engineers and scientists, helping users at all levels to strengthen their grasp of the subject. … One of its best aspects is the large number of worked examples … The many problems at the end of each chapter will also make the book attractive for an undergraduate engineering course. … Those who want to be able to perform their own calculations and make estimates without using a commercially available software package will find this book invaluable. It will help them to understand the relevant thermal mechanisms and save considerable time by solving frequently encountered thermal design problems in real equipment in an efficient manner. … This is a book well worth owning.

—John J. Shea, in IEEE Electrical Insulation Magazine, Jan/Feb 2012, Vol. 28, No. 1

Introduction

Primary mechanisms of heat flow

Conduction

Application example: Silicon chip resistance calculation

Convection

Application example: Chassis panel cooled by natural convection

Application example: Chassis panel cooled only by radiation 7

Illustrative example: Simple thermal network model for a heat sinked power transistor

Illustrative example: Thermal network circuit for a printed circuit board

Compact component models

Illustrative example: Pressure and thermal circuits for a forced air cooled enclosure

Illustrative example: A single chip package on a printed circuit board—the problem

Illustrative example: A single chip package on a printed circuit board—Fourier series solution

Illustrative example: A single chip package on a printed circuit board—thermal network solution

Illustrative example: A single chip package on a printed circuit board—finite element solution

Illustrative example: A single chip package on a printed circuit board—methods compared

Thermodynamics of airflow

The first law of thermodynamics

Heat capacity at constant volume

Heat capacity at constant pressure

Air temperature rise: Temperature dependence

Air temperature rise: T identified using differential forms of ΔT,ΔQ

Air temperature rise: T identified as average bulk temperature

Airflow I: Forced flow in systems

Preliminaries

Bernoulli’s equation

Bernoulli’s equation with losses

Fan testing

Estimate of fan test error accrued by measurement of downstream static pressure

Derivation of the "one velocity" head formula

Fan and system matching

Adding fans in series and parallel

Airflow resistance: Common elements

Airflow resistance: True circuit boards

Modeled circuit board elements

Combining airflow resistances

Application example: Forced air cooled enclosure

Airflow II: Forced flow in ducts, extrusions, and pin fin arrays

The airflow problem for channels with a rectangular cross-section

Entrance and exit effects for laminar and turbulent flow

Friction coefficient for channel flow

Application example: Two-sided extruded heat sink

A pin fin correlation

Application example: Pin fin problem from Khan, et al.

Flow bypass effects according to Lee

Application example: Flow bypass method using Muzychka and Yovanovich correlation

Application example: Flow bypass method using HBT friction factor correlation

Flow bypass effects according to Jonsson and Moshfegh

Application example: Pin fin problem using Jonsson and Moshfegh correlation

Airflow III: Buoyancy driven draft

Application example: Buoyancy-draft cooled enclosure

System models with buoyant airflow

Forced convective heat transfer I: Components

Forced convection from a surface

The Nusselt and Prandtl numbers

The Reynold’s number

Classical flat plate forced convection correlation: Uniform surface temperature, laminar flow

Empirical correction to classical flat plate forced convection

correlation, laminar flow

Application example: Winged aluminum heat sink

Classical flat plate forced convection correlation: Uniform heat rate per unit area, laminar flow

Classical flat plate (laminar) forced convection correlation extended to small Reynold’s number

Adiabatic heat transfer coefficient and temperature according to M. Faghri, et al.

Adiabatic heat transfer coefficient and temperature according to R. Wirtz

Application example: Circuit board with 1.5 in. / 1.5 in. / 0.6 in. convecting modules

Application example: Circuit board with 0.82 in./ 0.24 in. /0.123 in. convecting modules

Forced convective heat transfer II: Ducts, extrusions, and pin fin arrays

Boundary layer considerations

A convection/conduction model for ducts and heat sinks

Conversion of an isothermal heat transfer coefficient referenced to inlet to referenced to local air

Nusselt number for fully developed laminar duct flow corrected for entry length effects

A newer Nusselt number for laminar flow in rectangular (cross-section) ducts

Nusselt number for turbulent duct flow

Application example: Two-sided extruded heat sink

Flow bypass effects according to Jonsson and Moshfegh

Application example: Heat sink in a circuit board channel using the flow bypass method of Lee

In-line and staggered pin fin heat sinks

Application example: Thermal resistance of a pin fin heat sink

Natural convection heat transfer I: Plates

Nusselt and Grashof numbers

Classical flat plate correlations

Small device flat plate correlations

Application example: Vertical convecting plate

Application example: Vertical convecting and radiating plate

Vertical parallel plate correlations applicable to circuit board channels

Application example: Vertical card assembly

Recommended use of vertical channel models in sealed and vented enclosures

Conversion of heat transfer coefficients referenced-to-inlet air to referenced-to-local air

Application example: Enclosure with circuit boards - enclosure temperatures only

Application example: Enclosure with circuit boards - circuit board temperatures only

Application example: Enclosure with circuit boards, comparison with CFD

Application example: Single circuit board enclosure with negligible circuit board radiation

Illustrative example: Single circuit board enclosure with radiation exchange between interior enclosure walls and circuit board, results compared with experiment

Illustrative example: Metal walled enclosure with ten circuit boards

Illustrative example: Metal walled enclosure with heat dissipation provided

Natural convection heat transfer II: Heat sinks

Heat sink geometry and some nomenclature

A rectangular U-channel correlation from Van de Pol and Tierney

Design plots representing the Van de Pol & Tierney correlation

A few useful formulae

Application example: Natural convection cooled, vertically oriented heat sink

Application example: Natural convection cooled, nine fin heat sink compared to test data

Spacial effects and the view factor

Application example: View factors for finite parallel plates

Non-black surfaces

Application example: Radiation and natural convection cooled enclosure with circuit boards

Hottel script F (F) method for gray-body radiation exchange

Application example: Gray-body circuit boards analyzed as infinite parallel plates

Application example: Gray-body circuit boards analyzed as finite parallel plates

Thermal radiation shielding for rectangular U-channels (fins)

Application example: Natural convection and radiation cooled heat sink

Application example: Nine fin heat sink, compared with test data

Application example: Natural convection and radiation cooled nine fin heat sink

Illustrative example: Natural convection and radiation cooled heat sink

Conduction I: Some basics

Fourier’s law of heat conduction

Application example: Mica insulator with thermal paste

Thermal conduction resistance of some simple structures

The one-dimensional differential equation for heat conduction

Application example: Aluminum core board with negligible air cooling

Application example: Aluminum core board with forced air cooling

Application example: Simple heat sink

Fin efficiency

Differential equations for more than one dimension

Physics of thermal conductivity of solids

Thermal conductivity of circuit boards (epoxy-glass laminates)

Application example: Epoxy-glass circuit board with copper

Thermal interface resistance

Application example: Contact resistance for an aluminum joint

Circular-source, semi-infinite media solution by Carslaw and Jaeger (1986)

Rectangular-source, time dependent, semi-infinite media solution by Joy & Schlig (1970)

Other circular source solutions

Rectangular source on rectangular, finite-media with one convecting surface: Theory

Rectangular source on rectangular, finite-media: Design curves

Application example: Heat source centered on a heat sink (Ellison, 2003)

Application example: IC chip on an alumina substrate

Rectangular source on rectangular, finite-media with two convecting surfaces: Theory

Exploring the difference between one-sided and two-sided Newtonian cooling

Including the effect of two different ambients to the two-sided spreading theory

Application example: Heat sink with two convecting sides, one finned and one flat

Square source on square, finite-media with one convecting surface - time dependent (Rhee and Bhatt, 2007)

Illustrative example: A simple steady-state, thermal network problem, solutions compared

Thermal networks: Time-dependent theory

Illustrative example: A simple time-dependent, thermal network problem

Finite difference theory for conduction with Newtonian cooling

Programming the pressure/airflow network problem

Finite element theory - the concept of the calculus of variations

Finite element theory - derivation of the one-dimensional Euler-Lagrange equation

Finite element theory - application of the one-dimensional Euler-Lagrange equation

Finite element theory - derivation of the two-dimensional Euler-Lagrange equation

Finite element theory - application of the Euler-Lagrange equation to two dimensions

Appendices

Bibliography

Index

Gordon N. Ellison has a BA in Physics from the University of California at Los Angeles (UCLA) and an MA in Physics from the University of Southern California (USC). His career in thermal engineering includes eight years as a Technical Specialist at NCR and 18 years at Tektronix, Inc., retiring from the latter as a Tektronix Fellow. Over the last 15 years Mr. Ellison has been an independent consultant and has also taught the course, Thermal Analysis for Electronics, at Portland State University, Oregon. He has also designed and written several thermal analysis computer codes.