Term Paper of Heat & Mass

8/8/2019 Term Paper of Heat & Mass

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contentIntroduction

IBM research

Deep computing

Bio array chip reaction

Series-connectd heat dissipator

I. Thermal management of computer chip

II. Cooling multi chip using heat pipes

III. Water cooling radiator for computer-chip

IV. Heat transfer engineering in modern laptops

V. Turbo computer

VI. conclusion


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Introduction

The technique, called "high thermal conductivity interface technology,"

allows a twofold improvement in heat removal over current methods.

This paves the way for continued development of creative electronic

products through the use of more powerful chips without complex and

costly systems simply to cool them.

As chip performance continues to progress according to Moore's Law,

efficient chip cooling has become one of the most vexing problems for

designers of electronic products. The IBM technique outlined today is

one of several being explored by scientists from IBM Research - Zurich

to address the issue.

"Electronic products are capable of amazing things, largely because of

the more powerful chips at their heart," said Bruno Michel, manager of

the Advanced Thermal Packaging research group at IBM's Zurich lab.

"We want to help electronics makers keep the innovations coming. Our


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chip-cooling technology is just one tool at our disposal to help them do

that."

IBM research

The approach used by IBM addresses the connection point between the

hot chip and the various cooling components used today to draw the heat

away, including heat sinks. Special particle-filled viscous pastes are

typically applied to this interface to guarantee that chips can expand and

contract owing to the thermal cycling. This paste is kept as thin as

possible in order to transport heat from chip to the cooling components

efficiently. Yet, squeezing these pastes too thin between the cooling

components and chip would damage or even crack the chip if the

conventional technologies are used.


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Using sophisticated micro-technology, the IBM researchers developed a

chip cap with a network of tree-like branched channels on its surface.The pattern is designed such that when pressure is applied, the paste

spreads much more evenly and the pressure remains uniform across the

chip. This allows the right uniformity to be obtained with nearly two

times less pressure, and a ten times better heat transport through the

interface.

This unique and extremely powerful design for chip cooling is borrowed

from biology. Systems of hierarchical channels can be found manifold in

nature, e.g. tree leaves, roots, or the human circulatory system. They can

serve very large volumes with little energy, which is crucial in all

organisms larger than a few millimeters. Ancient water irrigationsystems also used the same approach.


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The demonstrated prototype is part of a large effort within IBM's

Research and Development organizations to improve cooling

performance of next and future generations of computer systems.

Deep computing

The cooling bottleneck results from the demand for ever more powerful

computer chips and becomes one of the most severe constraints of

overall chip performance. Today's high-performance chips already

generate a power density of 100 Watts per square centimeter one

order of magnitude more than that of a typical hotplate. Tomorrow's

chips may attain even higher power densities, which would create

surface temperatures close to that of the sun when not cooled (approx.

6000 C). Current cooling technologies, mainly based on forced air

convection (fans) blowing across heat sinks with densely spaced fins,

have essentially reached their limits with the current generation of

electronic products. To make matters worse, energy needed to cool

computer systems is rapidly approaching the power used for

calculations, thus almost doubling the overall power budget.


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"Cooling is a holistic challenge from the individual transistor to the

datacenter. Powerful techniques, brought as close as possible to the chip

right where the cooling is needed, will be crucial for tackling the power

and cooling issues," states Michel.

Looking beyond the limits of air-cooling systems, Zurich researchers are

taking their concept of branched channel design even further and are

developing a novel and promising approach for water-cooling. Called

direct jet impingement, it squirts water onto the back of the chip and

sucks it off again in a perfectly closed system using an array of up to

50,000 tiny nozzles and a complicated tree-like branched return

architecture.

Bio array chip reactionBy developing a perfectly closed system, there is also no fear of coolant

getting into the electronics on the chips. What's more, the IBM team was

able to enhance the cooling capabilities of the system by devising ways


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to apply it directly to the back of the chip and thereby avoiding the

resistive thermal interfaces in between the cooling system and the

silicon.

First lab results are impressive. The team has demonstrated cooling

power densities of up to 370 Watts per square centimeter with water as

coolant. This is more than six times beyond the current limits of air-

cooling techniques at about 75 Watts per square centimeter. Yet, the

system uses much less energy for pumping than other cooling systems

do.

A cooling assembly for cooling an electronic component with direct air

comprising; a housing, at least one electronic component disposed in

said housing, a nozzle supported in said housing for directing cooling air


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over said electronic component, an open air cycle cooling unit disposed

in said housing for supplying the cooling air to said nozzle, said cooling

unit including a casing and a compressor rotatably supported by said

casing for moving air, wherein said casing includes opposite casing ends

and a casing axis extending therebetween, a shaft extending along said

casing axis between said shaft and said compressor being supported on

said shaft, said air bearings being between said shaft and said casing, air

bearings supporting said compressor in said casing on a thin film of air

for maintaining a contaminate free housing, an electric motor disposedin said casing for rotating said shaft, and an expander supported on said

shaft for reducing pressure of air that flows through said expander.


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Series connected heat dissipater

A cooling assembly for cooling electronic components with direct air comprising; a housing of metal and having a generally rectangular

periphery to define four corners and including a housing bottom and a

housing top with spaced and parallel side walls being solid and


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extending between said housing bottom and said housing top, said

housing having opposite housing ends and a housing axis with said

housing bottom and said side walls and said housing top extending

axially between said housing ends to define an air entrance at one of said

housing ends and an air exit at the other of said housing ends to allow

the flow of air through said housing, an entrance plate of metal and

disposed at said air entrance and having a plurality of entrance apertures

for the flow of air through said air entrance, an exit plate of metal and

disposed at said air exit and having a plurality of exit apertures for theflow of air through said air exit, a first electronics box disposed at a first

corner adjacent a first side wall and said air entrance for providing

electric signals to said assembly, a second electronics box disposed at a

second corner adjacent said first side wall and said air exit for providing

electric signals to said assembly, a plurality of electronic components

disposed within said housing, said components including a mother board

disposed on said housing bottom, said components including a plurality

of circuits disposed on said mother board, said components including a

plurality of electronic chips disposed on said mother board, a plurality of

cold plates having a plurality of heat transfer fins disposed on said chips,

an open air cycle cooling unit disposed in said housing for cooling theair that cools said electronic components, said cooling unit including a

plurality of fans disposed side-by-side between said second electronics

box and a second side wall and parallel to said exit plate for moving air


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through said exit plate, said cooling unit including a heat exchanger for

cooling air and disposed between said plurality of fans and said exit plate and including a heat exchanger inlet and a heat exchanger outlet

for the flow air through said heat exchanger, said cooling unit including

a casing having opposite casing ends and a casing axis extending parallel

to said housing axis and supported on said housing bottom between said

plurality of fans and said air entrance, a shaft being rotatably supported

along said casing axis between said casing ends, a compressor mounted

on said shaft at the one of said casing ends nearer said air entrance and

having a compressor inlet and a compressor outlet for compressing air, a

expander mounted on said shaft at the one of said casing ends nearer

said air exit and having an expander inlet and an expander outlet for

reducing the pressure of air that flows through said expander and for rotating said shaft, an electric motor disposed between said compressor

and said expander in said casing for rotating said shaft, said cooling unit

including a nozzle having a nozzle inlet and a plurality of nozzle outlets


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disposed over said cold plates for distributing air over said cold plates, a

first air tube interconnecting said compressor outlet to said heat

exchanger inlet for the flow of air

a second air tube interconnecting said heat exchanger outlet to said

expander inlet for the flow of air therebetween, a third air tube

interconnecting said expander outlet to said nozzle inlet for the flow of

air therebetween, and air bearings supporting said shaft on a thin film of

air for maintaining a contaminate free air stream, said air bearings

including a plurality of journal bearings for supporting the radial load of

said shaft and a plurality of thrust bearings for supporting the axial load

of said shaft.

Thermal management of computer chip

Electronic systems, such as computer systems, usually employ a number

of electrical components that generate heat. Excessive heat accumulated

therein will adversely affect operation of the computer system, and may

cause the computer system to be unstable. Therefore, heat dissipation


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assemblies are widely used for dissipating heat from heat-generating

devices of a computer system to outside thereof. Typically, a heat

dissipation assembly such as a heat sink is disposed on the heat-

generating device for heat dissipation.

Nowadays, developments in computer chip technology have provided

computer central processing units (CPUs) with more functions and faster

processing speeds. Accordingly, modern CPUs generate copious

amounts of heat. Generally speaking, a heat-generating quantity of a

CPU is in a range from 50 to 90 Watts, which results a surface

temperature of the CPU of approximately 40 to 80 degrees Celsius. For

example, the heat-generating quantity of a Pentium IV 2.8 G CPU is

about 68 Watts, and a surface temperature of the CPU configured with a

conventional heat dissipation assembly is about 70 degrees Celsius.

Such a high surface temperature may adversely affect operation of thecomputer system, thus a heat dissipation assembly having very high heat

dissipation efficiency is becoming increasingly important.

Heat transfer engineering in moden laptops

A typical computer system--personal computer, monitor, and printer--can use as much as 1,000 kWh of electricity each year. And despite this

high consumption, consumers often base their buying decisions on initial

cost and equipment features rather than on energy efficiency. To


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encourage manufacturers to produce more energy-efficient computer

equipment and consumers to purchase them, the U.S. Environmental

Protection Agency (EPA) is developing the EPA Energy Star Computers

program. Manufacturers who have signed a commitment contract with

EPA and whose equipment meets the established efficiency criteria--

personal computers with the ability to enter a low-power state of 30 W

or less, for example--will display an EPA Energy Star Pollution

Preventer logo, making it easy for consumers to distinguish energy-

efficient from inefficient equipment. The program, which is still beingdeveloped, has an estimated potential to save 25 billion kWh and reduce

carbon dioxide emissions by 20 million tons each year.

Conclusion

In another aspect, fuel cells are more and more popular as a green

energy source, particularly for portable electronic devices. Compared

with the secondary cells which need a considerable time to recharge, the


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fuel cells have advantages of continuous power supply and quick

refilling of fuel. A fuel cell is an electrochemical device for continuously

converting chemical energy into electrical energy at a suitable reaction

temperature. Currently, fuel cells can be classified into proton exchange

membrane fuel cells (PEMFCs), alkaline fuel cells (AFCs), direct

methanol fuel cells (DMFCs), etc. Generally, a fuel cell includes a cell

base, a fuel cartridge for supplying fuel to the cell base, and an external

heater for heating the fuel up to a reaction temperature, which is

approximately in a range from 50 to 120 degrees Celsius. The cell basegenerally includes an anode, a cathode, an electrolyte sandwiched

therebetween, and an external circuit connected to the anode and the

cathode. The fuel is fed to the anode, and an oxidizer is fed to the

cathode. However, the external heater consumes an amount of electrical

energy, thereby an energy utilization efficiency of the fuel cell is

lowered in a sense.

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Term Paper of Heat & Mass