Central Texas College Heat Transfer Worksheet

Heat Transfer II Heat Sink Project, Winter 2020Problem Statement:
This will be an individual project. The purpose of this project is to tie together many of the
concepts you have learned in your fluid-thermal courses in an open-ended project. The final
reporting out on this project is TBD.
You have a hot computer chip that is made from silicon, and you need to design a heat sink to
remove 97.8±1.4 Watts in order to keep it below a maximum temperature of 60.0°C (use this
temperature as the “base temperature” for your heat sink calculations). There is a fan blowing
air over the chip at a velocity of Vd = 2.80 m/sec, and at a temperature of 27.0°C; assume that
the atmospheric pressure is sea-level standard (101.325 kPa). The computer chip is inside an
enclosure which is open in the front and back (direction of air flow from the fan); see Figure 1
below for a schematic.
You are working for a company that will design and manufacture these heat sinks. You are
required to create the scenario that they will be used for, and determine what characteristics
will be important for your company (high/low production rate, weight of heat sink, cost, etc).
You will pick 3 materials/designs that you think will meet your intended usage, and then use a
design decision matrix to select the “best” material/design.
The dimensions shown on Figure 1 are:
Hd = 20.0 cm (height of enclosure)
Wd = 25.0 cm (width of enclosure)
Ld = 20.0 cm (not shown on Figure 1, length of enclosure)
Whs = 15.0 cm (Width of heat sink)
tb = 8.0 mm (base thickness of the heat sink)
Hf = To be determined by the student (height of fins; shown as “L” in our textbook)
Lhs = 16.0 cm (not shown in Figure 1, Length of heat sink fins; shown as “w” in our
textbook)
b = To be determined by the student (space between the fins)
tf = To be determined by the student (thickness of the fins; shown as “t” in our
textbook)
Assume that the fins are parallel to the direction of airflow. Perform the following calculations:
Calculate the convection coefficient for a flat plate using the conditions shown above.
Assume that the heat sink will slow down the airflow to 70% of its freestream velocity;
this decreased air velocity is shown on Figure 1 as Vf . In order to keep this loss at 70%
of the freestream velocity, the gap between the fins should be at least 10.0 mm; and
due to manufacturing constraints the minimum fin thickness allowable is 5.0 mm. For
economic reasons use a straight rectangular fin.
Choose 3 materials to make the heat sink from (note that a heat sink is also called a “fin
array”); you will compare the your 3 materials/designs using a design decision matrix to
determine which best meets your intended usage.
Use your calculated convection coefficient and your choice of material, along with an
assumed fin size (thick “t” and height “L”) to calculate the fin efficiency. Size a
rectangular finned heat sink similar to the one shown in Figure 3.21 from section 3.6 in
your textbook.
Finally, use this fin efficiency and an estimated fin array layout to calculate the total
heat transfer rate from your array (i.e. determine how many fins will be in your array,
using the restrictions above on the fin thickness, spacing allowed between fins, and the
width of the fin array). The calculated heat transfer rate should be equal to 97.8 ±1.4
Watts; this value includes a factor of safety and an allowance for growth.
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We will ignore any resistance due to contact resistance and due to the thickness of the
base of the heat sink.
As a required part of your report/presentation, suggest a scheme for attachment of the
heat sink to the chip, and discuss why you chose it (i.e. to minimize contact resistance,
cost, reliability, etc.; also thermal paste including a reference for what you chose).
Finally, we will ignore any radiation effects since our temperature difference is only
about 33 degrees Celsius.
Figure 1 Heat Sink Geometry (Rectangular Fin Array)
Report format (if assigned):
Title page: To, From, Subject, Date
Introduction section: The introduction section should include as a minimum your
problem statement, any assumptions you are making, and describe how you will solve
your problem.
Results section: Show the results to your problem here. This section as a minimum
should include the 3 materials you chose for your heat sink (and why you chose them), a
design decision matrix showing which material/design best meets your intended usage,
a sketch/CAD drawing of your “best” solution (including dimensions), and a short
discussion on how your design solves your problem (and any limitations to your design).
Include a brief discussion on how you will attach the heat sink to the chip.
References: Properly document any reference material in the Reference section.
Appendix: Include your calculations, computer print-outs (if appropriate), etc that you
used to produce your design.
This is a short “work “report so you do not have to include a table of contents, list of
figures, etc that would be expected for a longer, more formal report.
Your project report will be graded with the help of the attached Rubric; note that there are five
areas that will be evaluated. If the final reporting out is a presentation you will need to address
the items as shown above in the Report Format, and address the 5 categories shown below in
the Rubric for Solving Engineering Problems. More details on the reporting for this project will
be released later in the quarter. Your report/oral presentation (TBD) will also be graded using
the communications Rubric shown below.
Proficiency Scale
4 High proficiency
3 Proficiency
2 Some proficiency
1 Limited or no proficiency
Rubric for Solving Engineering Problems
Based on the OIT ESLO Communication rubric developed by the ESLO Communication Committee (approved by the Assessment Executive Committee, November 2016)
EAC SLO 03 An ability to communicate effectively with a range of audiences
EAC SLO g: An ability to communicate effectively
Performance Criteria
(1) Limited or No
Proficiency
(2) Some Proficiency
(3) Proficiency
3a) Purpose and
Audience
• Purpose is unclear or
requires substantial
inference from the
audience.
• Intended audience is
unclear or overly broad.
• The work would not be
meaningful or useful to
the intended audience.
• The work omits or
dismisses key audience
concerns.
• Purpose may be inferred, but is not clearly stated
• Minor changes in approach or medium would make
the work more meaningful or useful to the intended
audience.
• Some content is too advanced/basic for the intended
audience.
3b) Focus and
Organization
• Organizing element is
underdeveloped,
inconsistent, or missing.
• Order and structure are
unclear.
• Digressions
compromise or obscure
the work’s purpose.
• Transitional elements
are underdeveloped,
inconsistent, or missing.
• Organizing element is present, but needs
development (it is too broad, narrow, or trivial).
• Minor gaps in organization detract from the
effectiveness of the work.
• Minor changes in organization would clarify the
hierarchy of claims and information.
• Minor changes in transition language would improve
the work (transitions between key ideas are choppy
or abrupt).
(4) High Proficiency
• Content serves a
specific, identifiable
purpose (e.g., inform,
persuade, analyze).
• Purpose and content
are appropriate to the
needs of a specific,
identifiable, and
appropriate audience.
• Content is tailored to
the level of expertise,
authority, and values of
the audience.
• Communication
medium (essay, memo,
report, speech, etc.)
matches purpose
and audience.
• Content is focused on a
specific and appropriate
organizing element: a
thesis statement, purpose
statement, or theme.
• Content is organized so
that ideas relate clearly to
each other and to the
organizing element.
• Distinctions between
major and minor claims
Score
Based on the OIT ESLO Communication rubric developed by the ESLO Communication Committee (approved by the Assessment Executive Committee, November 2016)
3c) Support and
Documentation
3d) Style and
Conventions
• The work includes
frequent instances of
unsupported claims or
key missing details.
• The work relies on
evidence that lacks rigor,
based on the audience’s
or discipline’s standards.
• The work relies on
demonstrably biased
evidence (without
providing appropriate
context or qualification of
that evidence).
• The work treats sources
with bias, or
demonstrates incomplete
understanding of source
material.
• The work does not meet
academic citation or
disciplinary standards.
• (Where students have a
choice in form or
medium) the choice or
form or medium is
inappropriate to
audience, purpose, or
context.
• The work includes few instances of claims
unsupported by appropriate evidence.
• Additional or more carefully chosen details would
improve the work.
• The work includes (but does not rely on) evidence
that lacks rigor, based on the audience’s or discipline’s
standards.
• Additional context or discussion of credentials for
sources of evidence would add value to the work.
• The work contains few, minor documentation errors
(according to academic citation style or disciplinary
approach).
• (Where students have a choice in form or medium) a
minor change in form or medium would make the
work more accessible or engaging to the audience.
• Minor changes in terminology, word choice,
sentence structure, or tone would improve the work.
are clear, providing
consistent focus in
content.
• Transition language
(and other organizing
elements, such as
headings or lists)
throughout organizes
ideas and guides
audience understanding.
• Claims are consistently
supported with
appropriate, relevant,
and specific evidence,
whether drawn from
disciplinary knowledge,
careful reasoning, or
credible research.
• Evidence derived from
sources supports and
develops original content.
• Source material is
credible; it is introduced
and interpreted to
provide context.
• Source material is
documented accurately
according to the
appropriate conventions
(academic citation style
or disciplinary approach).
• Students deliver
content in spoken,
written, or visual forms
and media, as
appropriate to context.
• Use of language
(terminology and word
Based on the OIT ESLO Communication rubric developed by the ESLO Communication Committee (approved by the Assessment Executive Committee, November 2016)
3e) Visual
Communication (where
appropriate)
• Terminology, word
choice, sentence
structure, or tone are not
in keeping with
professional or academic
expectations for the
work.
• Written: prevalent or
distracting spelling,
grammar, syntax, usage,
and/or mechanics errors
compromise the work’s
impact, credibility, or
coherence.
• Oral: prevalent or
distracting verbal and/or
non-verbal delivery
issues compromise the
work’s impact, credibility,
or coherence.
• The work includes any
visuals that are
inappropriate to
audience or context.
• Necessary visuals are
missing from the work.
• Most (or all) visuals in
the work serve a purely
aesthetic purpose, and
relate only tangentially to
the work’s purpose and
content.
• The work presents most
(or all) visuals without
context or interpretation.
• The work presents most
(or all) visuals without
documentation
(according to academic
• Written: the work contains minor, isolated errors in
spelling, grammar, syntax, usage, and/or mechanics;
an editing pass would improve the work.
• Oral: the work contains minor, isolated issues in
verbal and/or non-verbal delivery; additional
preparation or practice would improve the work.
choice, sentence
structure, etc.) is clear
and professional,
demonstrating mastery of
content and form.
• Written: students
demonstrate correct
grammar, spelling,
syntax, usage, and
mechanics.
• Oral: both verbal and
nonverbal delivery
demonstrate poise,
preparation, mastery of
material and audience
awareness/ engagement.
• Minor changes in content, organization, or
appearance would enhance the visuals in the work.
• Additional or more carefully-chosen visuals would
improve the work.
• Some (but a minority of) visuals in the work serve a
purely aesthetic purpose, and relate only tangentially
to the work’s purpose and content.
• Additional context and interpretation of visuals
would improve the work.
• The work contains few, minor documentation errors
of visuals, or the information presented in visual
format (according to academic citation style or
disciplinary approach).
• High quality visuals are
employed to illustrate,
contribute to, or develop
content, and not for
purely aesthetic appeal.
• All visuals are
appropriately introduced
and interpreted.
• All visuals are
documented according to
the appropriate
conventions (academic
citation style or
disciplinary approach).
Based on the OIT ESLO Communication rubric developed by the ESLO Communication Committee (approved by the Assessment Executive Committee, November 2016)
3f) Justification (SelfAssessment)
citation style or
disciplinary approach).
• Student omits
discussion of multiple
ESLO criteria.
• Student’s selfevaluation is cursory,
facile, or is compromised
by lack of insight (student
overlooks obvious
deficiencies in the work).
• Student demonstrates
an inability or
unwillingness to elicit or
use feedback to improve
the work.
• Student omits evaluation of one ESLO criterion.
• Student’s self-evaluation would be improved by a
more rigorous analysis.
• Student’s self-evaluation addresses only process, or
only product, but does not address both.
• A more rigorous approach to eliciting and using
feedback would improve the work.
• Articulate a clear
rationale for
communication choices
(purpose and audience,
focus and organization,
support and
documentation, style and
conventions, and visual
communication).
• Self-assess the quality
of their work (including
process and product).
• Elicit and effectively use
feedback to improve their
work.