ME4225-1-Introduction.pdf

2013 Prof Andrew Tay ME4225 Industrial Heat Transfer 1

Department of Mechanical Engineering, NUS

ME 4225 Industrial Heat Transfer

Professor Andrew Tay

Department of Mechanical Engineering

National University of Singapore

Office: EA-07-19

Phone: 6516-2207

Email: [email protected]


Course Outline

A. Electronics Cooling

Heat Transfer with special application to electronics cooling industry.

However, application of principles/techniques to other industrial heat

transfer problems are within the scope of this module.

1. Introduction

2. Conduction Cooling

3. Free and Forced Convection Cooling

4. Radiation Heat Transfer

5. Combined Modes of Heat Transfer

B. Transient Heat Conduction

beyond lumped capacitance method


Course Outline - Continued

C. 2D Steady Heat Conduction

numerical method of solution

D. Boiling Heat Transfer (Drs PS Lee & SY Park)

1. Pool boiling.

2. Film boiling and condensation

3. Two phase flow and heat transfer (flow boiling)

E. Mass Transfer

1. Diffusive and convective mass transfer

2. Analogy between heat and mass transfer

3. Evaporative cooling


Module Learning Outcomes

1.Ability to analyze heat flows through various components in a

thermal system involving one or more modes of heat transfer.

2. Ability to analyze transient and 2D steady heat transfer

problems.

3. Ability to analyze heat transfer problems involving boiling and

condensation.

4. Ability to understand the analogy between heat and mass

transfer and solve mass transfer problems.

Assessment: 2 quizes (15% each); final examination (70%)


1. D. S. Steinberg,

Cooling Techniques for Electronic Equipment 2e, J. Wiley & Sons, 1991

2. F.P. Incropera, D.P. Dewitt, T.L. Bergman, A.S. Lavine,

"Principles of Heat and Mass Transfer 7e, J Wiley & Sons, 2013.

3. Holman, J.P., Heat Transfer, McGraw-Hill, New York, 10e, 2010.

References


With the relentless trend toward ever powerful chips in ever decreasing

package sizes, intense heat fluxes and higher operating temperatures

are becoming a concern.

Thermal Challenges in Electronics Systems

Heat dissipation of

Intel CPUs.

W

80 W/cm2


Newspaper Article on 2004 Intel Chip


Humidity

19%

Vibration

20%

Dust

6%

Temperature

55%

Dust

Vibration

Humidity

Temperature

Major Causes of Electronics Failures

Thermally induced failures account for more than 50% of all electric

failures. The useful life of an electronic component is halved for

every rise of 10C in its operating temperature.


Perspective on Microelectronic Heat Fluxes

Unlike other systems

the temperature of

chips cannot be

increase even while

heat fluxes are

increased.

Heat flux, q = h T


Values of Heat Transfer Coefficient for Various

Cooling Technologies

FC = Fluorocarbon fluid

s

thhA

R1


Structure of IC Packages


Chip Carrier or Package

Early design of IC package.

Pin-Through-Hole (PTH) technology used.


Small Outline Integrated circuit

(SOIC) using SMT Ceramic Dual in-line package (CerDIP)

using PTH technology

IC packages, chip carriers or modules hold semiconductor chips and

supply the connections or leads between the chip and printed circuit

boards. As number of leads increases, PTH technology is replaced by

Surface Mount Technology (SMT)

Conventional IC Packages


Leadless Chip

Carrier

Pin Grid Array (PGA)

J-Leaded

Plastic

Quad Flat

Package

(PQFP)

Plastic Dual-in-line

Packages (PDIP)


Ceramic Quad Flat Pack

Plane of heat dissipation

at IC layer on surface of

silicon chip


PCB

Copper Pads

Underfill

Solder

Joints

Flip Chip Package

Chip directly connected to PCB by solder ball joints.

Area array packaging to accommodate more chip-to-board interconnections.

Plane of heat dissipation

at IC layer on surface of

silicon chip


Flip Chip Package


Wirebonded Ball Grid Array (BGA)

Plane of heat dissipation at IC layer on

surface of silicon chip


Flip Chip Ball Grid Array (BGA)


Fully Populated and Depopulated BGA

Fully-populated BGA where

solder balls cover the entire

substrate

Depopulated BGA. Often the

central patch of solder balls

serve a thermal function rather

than an electrical function.


Stacked Die Packages


Stacked Flip-Chip CSP

CSP = Chip Scale Package


Package-on-Package (PoP)


Examples of Electronics Cooling Systems

Electronic box cooled with exhaust fan


Water or Refrigerant Cooling Systems


Electronic Boxes in Missiles

Plan view of electronic box with cover removed


Coolers for PC CPUs Fan-Cooled Heat Sink

heat sink

fan

CPU


Heat Pipes


heat sink

Coolers for PC CPUs Heat Pipes

fan

heat pipes

CPU


heat exchanger

Heat Pipe Coolers for Notebook Computers

fan

heat pipes

Copper block

for CPU


Coolers for PC CPUs Thermoelectric Coolers

qp qp

qsink = qp

Pe

qsink = qp + Pe

Seebeck and Peltier effects.

A bigger heat sink will be necessary with thermoelectric cooling.


Thermoelectric CPU Cooler for AMD Athlon

XP

Coolers for PC CPUs

Thermoelectric Coolers

heat sink

TE Cooler

CPU


Liquid Cooling

Source: Thermacore


Liquid Cooling

Source: Electronics Cooling


Immersion Cooling

Source: Electronics Cooling

CRAY-2 liquid immersion cooling system

Boiling may

occur.


Review of

Modes of Heat Transfer


Conduction Heat Transfer Thermal energy exchange from region of high temperature to

region of low temperature by the vibration of atoms/ions/molecules

and by the drift of electrons (metals)

Fouriers Law of Heat Conduction

Heat flux Temperature gradient

Heat flux, (1.1)

or heat rate, (1.2)

where k is the thermal conductivity of the material.

x

Tkqx

x

TkAqx


W/m K

W/m K

Aluminum (pure)

216

Alloy 42

16

Alumina

25

Mylar

0.2

Bakelite

0.2

Nickel

92

Beryllia

230

Nylon

0.2

Copper

398

Platinum

69

Diamond

2300

Quartz

1.0

Epoxy (no fill)

0.2

Silicon (undoped)

144

Epoxy (high fill)

2.1

Silicone grease

0.2

Glass- epoxy

1.7

Silicone rubber

0.2

Gold

297

Silver

418

Kovar

16.4

Solder (37% Pb, 63% Sn)

53

Lead

34

Teflon

0.2

Magnesium (cast)

70

Thermal grease/paste

1

Mica

0.5

Tin

63

Thermal Conductivity of Packaging Materials at 25C


W/m K

Water

0.60

Freon 113

0.073

FC-72

0.055

FC-75

0.057

FC-77

0.057

Mineral Oil

0.15

Thermal Conductivity of Selected Liquids at 25C


Measured at (C)

W/m K

Air

0

0.024

100

0.030

Argon

0

0.017

63

0.019

Helium

7

0.144

56

0.159

Hydrogen

4

0.168

50

0.186

Thermal Conductivity of Selected Gases at 1 atm.


Convection Heat Transfer

Convection thermal energy exchange between solid

surface and fluid as a result of the motion of the fluid relative

to the solid surface.

Forced convection

Motion of fluid artificially induced

e.g. by fan, pump.

Free (natural) convection

Motion of fluid induced by

buoyancy forces.


Flow Regimes

Flow can be

Laminar or Turbulent

Smooth, orderly flow. Disorderly, mixing flow

Internal or External

Flow in tubes, ducts. Flow over surfaces.


Heat flux, q = h (Tw Tf ) [W/m2] (1.3)

Heat transfer rate, q = h A (Tw Tf ) [W] (1.4)

where h = convective heat transfer coefficient

[W/m2K]

Tw = temperature of wall surface

Tf = bulk temperature of fluid

Newtons Law of Cooling

Heat flux Temperature difference


Radiation Heat Transfer

No medium required for radiation heat transfer.

Stefan-Boltzmann Law of black body radiation

Emissive power, eb = T4 (1.5)

where T is absolute temperature [K]

is S-B constant = 5.67 x 10-8 [W/m2.T-4]

A black surface is one which absorbs all thermal radiation incident on it.


Radiation exchange between surfaces

Radiation heat transfer between two black surfaces

Q = A1F12 (T14 - T2

4 ) (1.6)

where A1 is area of surface 1, and

F12 is a Shape or View Factor between the surfaces.

Radiation heat transfer is usually negligible when

temperature differences are not large. However, they can

be of the same order as natural convection heat transfer.

Documents

ME4225-1-Introduction.pdf