2. 2
Abstract
The increasing demand of computing power leads to a higher demand of electric power running
through microprocessors. To combat this, the project team was tasked with the design,
analysis, building and testing of a device to minimize the operating temperature of an
electrically heated plate. The temperature at the top center of the plate was to be tested after
6 minutes, while a box fan is turned on from a distance of 12 inches after the first three minutes
of heating. The group tested various designs by adjusting fin arrays and plate thicknesses as
well as by adding small computer fans in various positions. The advantages, disadvantages, and
test results of each option were then compared to create the final product used during Design
Day. The final product showcased a thicker plate with a pin-fin array and an operating
temperature of 31.2°C, a mass of 169.2 grams, and a cost of $2.60 to create.
3. 3
Introduction
In today’s world, the increasing integration of computers into our lives has led the demand of
microprocessor computing speed to approximately double every two years. Microprocessors
are in technology all around us, from the alarm clock that starts our day off to the cars which
get us to work. This increased computing power leads to an increased electric power demand,
and therefore high amounts of heat created through the microprocessors. The challenge at
hand is to keep the temperature of these microprocessors at a reasonable operating
temperature. The design of many microprocessors include a heat dissipation strategy, such as a
heat sink, a continuously flowing fluid, or a powered fan. The ability to create effective heat
dissipation devices at a low cost has a critical impact on the success of companies when
manufacturing and selling at an industrial scale.
The project team is given an electric 20 Watt Kapton Flexible Heater to simulate the challenge.
The flexible heater is pressed between two thin aluminum plates which are each 2” by 3” and
will be heated for 6 minutes in a horizontal orientation. To expedite the heat transfer, a box
fan set a distance of 12” is turned on after the first 3 minutes. At 6 minutes, a thermocouple is
placed on the top center of the plate to take a temperature reading.
Figure 1. Kapton Flexible Heater
The heat transfer device created by the group is required to fit within a box of dimensions 14” x
14” x 12”, and must be self-sustaining after the start of the competition timer. The competition
takes into account most parameters which are critical to companies who have to solve a similar.
The group is evaluated on the device weight, device cost, and most importantly the operating
temperature of the device. The points regarding the operating temperature of the plate are
given 2.5x the value of the points regarding device weight and cost, to emphasize the ultimate
goal at hand.
The methods used to design, analyze, build, and test the device are outlined in the following
sections of the report.
Design Analysis
During the process of concept generation, each team member presented initial drawings which
utilized basic methods of heat dissipation. These initial drawings presented an overall idea,
without much attention given to specific details. Each of these basic concepts of design were
then to be analyzed for advantages and disadvantages using a decision matrix.
4. 4
Figure 2. Design ideas, A (Top left), B (Top Right), C (Bottom Left), D (Bottom Right)
Design A was the most complex of the concepts imagined by the team. The design was based
around the idea of a fluid running through a casing which surrounds the heated plate,
throughout the 6 minutes of heating. With this design, the team could either incorporate a
pump systemwhich would bring the fluid back through, or have a reservoir filled at the
beginning. With the reservoir approach, the flow rate over time must be calculated and there
must be a place for the fluid to exit into. This would lead to a very slow flow rate to keep the
fluid moving for 6 minutes. In addition, the manufacturing processes for this process would
become very complicated.
Design B combined the idea of a heat sink with a fluid. In this design, the heat sink is
suspending the plate from the reservoir. The fluid does not need to be circulated, which
eliminates the need for increased volume or a pump. In the sketch, cones are used to minimize
the contact with the base of the reservoir. Other shapes were also considered for the geometry
of fins. Various fluids were also considered in place of water. The focus of this design,
however, would be removing the heat from the bottom plate more than the top. There was
discussion of adding a heat sink on the top in combination with this design, but the weight
would significantly increase. Utilizing the air forced convection would be more advantageous
than a resting fluid.
5. 5
Design C was based around the idea of drawing the heat away from the plate to an outside
copper casing. Copper’s low specific heat capacity and high thermal conductivity relative to
cost would make it an efficient and lightweight material choice to draw the heat to. This would
also allow the group to increase the volume of material around the outside of the plate to hold
more heat. Finding raw copper materials for machining was difficult for the team, where
aluminum was in abundance. In addition, the design was drawing heat away from the outsides
of the plate, allowing the heat to still concentrate at the center of the heated plate.
Design D was to test various designs of heat sinks to the advantage of the air flow introduced at
3 minutes. With the horizontal flow, a heat fin array as shown in the figure above would help
push the heat out if oriented parallel with the air flow. In addition, the textbook was
referenced to understand the advantages of various fin array designs. If an axial flow is
introduced to the system, then a pin-fin design may be advantageous. A heat sink could be
applied to the bottom as well when the plate is elevated.
Table 1. Decision Matrix
Emphasis Design Scoring
Parameters A B C D A B C D
Function/Performance 5 4 3 4 5 20 15 20 25
Product Cost 4 1 3 4 4 4 12 16 16
Size 3 2 4 2 5 6 12 6 15
Weight 4 1 2 2 5 4 8 8 20
Manufacturability 3 1 3 3 4 3 9 9 12
Score: 37 56 59 88
The decision matrix took into account the following parameters:
1. Function/Performance – How well will the device dissipate the heat from the top
center? Will it function throughout the 6 minutes of testing reliably?
2. Product Cost – How much will each individual part cost? Parts such as batteries,
pumps, and pre-manufactured nuts and bolts can add up and hurt the final score
during the competition.
3. Size – Will the product fit within the 14” x 14” x 12” requirement? Do any of the
designs require something large such as a reservoir, pump, or fan?
4. Weight – How heavy will everything add up to be? The addition of fluids or thick
plates add to the weight significantly, hurting the final score.
5. Manufacturability – Is the design simple enough to allow the team to manufacture it
with the tools available at machine shop?
The importance of each of these parameters were also added to place more emphasis on the
parameters which will affect the final score the most. The operating temperature score was
the most important, followed by the weight and cost. Each of these three scores will be
compared for a final placing.
6. 6
The team gathered to compare the various design options based on the decision, keeping in
mind many further options and alterations could be made to each basic design. Doing so allows
the team to put a value to the quality of each approach. The scores showed that Design D,
involving some type of heat fins with the possibility of adding more components, seemed to be
the most beneficial by a substantial value.
There are many variations of fin arrays which the team could use over the small heated plate.
The group began by looking into various heat sinks and applications. On a computer repair
company’s website, the idea behind heat sinks is explained in an article called Heatsink 101.
While many basic heat sinks for computers are simply fin arrays, many become more
complicated. The design of these arrays plays to the advantage of the air flow which can be
created. An increased air flow through the fins also helps the heat dissipate more efficiently.
At this point, the team looked into increasing the air flow through the device. Adding an
increased airflow through small fans could give the group a significant advantage over groups
simply relying on the air flow from the box fan. In addition, there would not be a limitation on
how close these fans are placed.
It was determined that a fan approximately the size of the heated plate is the desired
dimensions, to strike a fair balance between weight and surface area which the air flow would
cover. After searching through computer stores and online catalogs, the team decided on two
70 mm ball bearing case fans, which created a 21.33 CFM flow rate and 3500 RPM at a weight
of only 35 grams each. These fans cost $10.96 each after tax.
Figure 3. Device Placement
The group then had to decide on whether a fin array or a pin-fin array will be utilized with the
fans. If only the box fan were being used, the rectangular fin array as shown in Design D would
be the best option. From a top-down view, adding fans to either side of the plate with
perpendicular air flow to the box fan’s would be ineffective as the air flow from the small fans
would be blocked by the first fin plate for the fan in. Attempts to increase the air flow by
placing the fans before and after the entrance to the flow would also be hindered as the box
fan seemed to only slow down the velocities of the mini fans when placed behind them.
Orientations in which the computer fans are placed on the top and bottom of the fin design
were determined to have the biggest gain from the increased air flow the fans offer.
Fan Out
Fan in
Plate Box Fan Box FanPlate
Fan
In
Fan
Out
7. 7
Figure 4. Computer Heatsink
Adding fans to the top or bottom of the plate with a heat sink now changes the horizontal flow
to an axial flow. With axial flow, pin-fins are far more advantageous. Many computer fans add
an axial fan facing upwards to draw the heat away from the plate. For manufacturability
purposes and access to materials, cylindrical pin fins were selected. Attaching the pin fins to
the plate mechanically would lead to a much higher product cost and weight, considering the
parts would be pre-manufactured metals. Therefore, high heat adhesives were considered.
Through researching various glues used to build computers, the team came across a low-cost
thermal adhesive which can operate at temperatures upward of 150°C. This Arctic Silver
adhesive is made with micronized metals, which would help fill small gaps between the pins
and the plate. The direct contact between the fin and plate with the glue as a medium would
serve as a better heat transfer medium than a fluid.
The pins were made from a long aluminum rod with a diameter of 0.25 inches. The rod was cut
into larger pieces based on iterations of testing using a bandsaw. Once the finalized dimensions
were selected, the pins were cut down using a clamp and hand-saw to achieve a better finish
and accuracy.
A thicker plate was found using scrap materials at the machine shop. The top plate from the
flexible heater was replaced with a plate approximately 3 mm thick, weighing in at
approximately 39 grams. This increased mass was outweighed by its significant impact on the
final temperature when running tests. The pins were attached and cured using the Arctic Silver
adhesive and a room temperature cure. In order to create a hole on the top center of the plate
after the pins were attached, a combination of a drill bit and flat head drill were used on a mill.
This hole was created to approximately 2.5 mm diameter with a depth leaving 1 mm to allow a
thermocouple to reach the location which would have been tested on the original plate.
The position of the plate relative to the box fan also needed to be considered. The original
design of the plate elevated the design to approximately 4 inches off the ground. This elevation
allowed significant airflow under the device to provide forced convection to both top and
bottom plates. However, minor alterations to the horizontal and vertical positions showed
different results during testing. Therefore, tests were further conducted to learn what the ideal
horizontal and vertical position of the plate relative to the box fan is. Using a velocity sensor,
the team found the design for the plate needed to be elevated such that the heated plate is 7
inches off of the table. The addition of elevation support would mean an increased weight
8. 8
value, and a lightweight material needed to be used. Balsa wood provides a very good
combination of low weight and low cost.
The process behind selecting number of pins along with geometric properties are further
discussed as an iterative process in the model building and testing sections of this report.
Discussion about how it was also decided that the weight of the fans would not decrease the
operating temperature by a significant enough value to add in the costs and weights is also
included.
The final design showcases 38 offset pins at a diameter of 6.35 mm on the top of the thick plate
inches. Each of these pins is 30 mm tall, provide a total of 0.023945419 m2 of increased surface
area to the air passing through.
The final design used during the competition showed very low total cost, at approximately
$2.60 per unit. These expenses included the thermal paste, aluminum stock, 4 screws, and
balsa wood stock.
Table 2. Device Cost
Material Mass (in gm) Cost ($)
copper
thermal paste 0.60211 $0.759
brass
aluminum 135.37 $0.254
screws
4 @
$0.069/screw $0.276
balsa wood
28 inch @
$1.69/yd $1.314
Total $2.602
Figure 5. Final Device
9. 9
Model Building
There are 3 main processes of heat transfer at work in this setup. Each of these must be
evaluated in order to further understand the theoretical heat transfer occurring, and to help
design an optimal heat transfer device.
The first is natural convection, in which flow is induced by buoyancy forces due to density
differences caused by temperature variations in the fluid. In this situation, the slowest method
of cooling the plate would be only by natural convection. Calculating the natural convection
temperature gives the group a starting point in order to understand the effects of forced
convection and transient heat conduction. Using energy balance, equation 1 compares the
power applied to the plate to its heat transfer coefficient (h), temperatures (T), and area (A).
Simple algebra further simplifies the Eqaution 2, which isolates the desired variable Ts (surface
area).
(1)
(2)
Two separate heat transfer coefficients must be found, since the value varies from top plate to
bottom plate. The heat transfer coefficient (Equation 3) is found by relating the Nusselt
number (NuL). The Nusselt number must be calculated using varying equations depending on
the plate and the range of the Rayleigh number (RaL) and characteristic length value, which are
found by using Equations 4 & 5.
(3)
(4)
(5)
The Nusselt number can then be determined using the equations provided in Equations 6-8.
This value is plugged into the respective heat transfer coefficient in Equation 2.
(6-8)
10. 10
Using the set-up provided, surface temperature (Ts), is actually found using an iterative loop.
The iterative loop requires a guessed surface temperature to start, which can then be used to
evaluate properties, Rayleigh number, Nusselt numbers, heat transfer coefficients, and finally
the surface temperature again. When the guess converges with the guess, the surface
temperature through natural convection is found.
Figure 6. Iteration Process for Natural Convection
Starting the guess for surface temperature at approximately 490K, the values were each
calculated using an iterative table in Excel. After increasing the K value by 0.5 each iteration,
the temperature guess and calculated values converged at after 26 iterations, at approximately
502.5K, or 229.35°C.
Table 3. Iteration Results for Natural Convection
Iteration TS Ra NuTop NuBottom hTop hBottom TS Convergence
26 502.5 93926.01 9.4534 4.72 14.476 7.238 502.281 -0.219
The next heat transfer process at work during this setup is forced convection. This process is
analyzed for after the 3-minute mark, when natural convection transitions to forced transition
due to the fan being turned on. Forced convection is a type of transport in which fluid motion
is generated by an external source such as a pump, fan, or suction device. In forced convection,
the convective heat transfer coefficient is considered, which is the same for both top plate and
bottom plate. Again, the energy balance shown in Equation 1 allows us to compare the power
to the surface temperature (Ts), convective coefficient (h), areas of the plate (ATop and ABottom).
The surface temperature is found by rearranging the energy balance to Equation 2.
11. 11
(9)
(10)
Next, a Reynolds (ReL) and Prandtl (Pr) number are needed (Equations 11 & 12) to calculate the
Nusselt number (NuL) as shown in Equations 13 & 14. The fluid velocity, u∞, is measured using
a velocity sensor.
(11)
(12)
(13-14)
Using an average of several measured velocities, the characteristic length, and properties of air
defined from natural convection, Reynolds and Nusselt numbers are calculated.
Table 4. Velocity of Box Fan, Plate Area, and Characteristic Length
u (Avg) 3.1 m/s
Area 0.004553276 m^2
L 0.065 m
The heat transfer coefficient was calculated by using the thermal conductivity, k, the Nusselt
number, and the characteristic length, giving a value of 36.76 W/(m2*K). The forced convection
leads to a calculated surface value of 359.75K, or 86.6°C.
Table 5. Forced Convection Results
Re Nu h Ts
12672.96 90.8459 36.757651 359.74868
The next part of forced convection analysis is the model building of fins. Fins are one of the
most effective methods for dissipating heat, because they provide more material for the heat
to transfer to as well as more surface area in contact with the fluid flowing through. This was
critical to the team to understand what to manufacture for the pin fins. The initial model must
be built before variables can be input to minimize the theoretical temperature.
12. 12
Even though fins are added on from the beginning, the convective heat transfer will continue
from the fins as well as from the part of the plate still exposed. This equation is shown in
Equation 15.
(15)
The area of the exposed plate is represented by Aplate while the surface area exposed by the fins
is Afins. The efficiency of fins efficiency is given by Equation 16, where the m value is found
through Equation 17.
(16)
(17)
In Equation 17, AS is given by the surface area of a fin, and AC is the cross-sectional area. Using
the above equations as well as geometrical equations to calculate areas, a mathematical model
was created on Excel. This model allows for the input of various fin geometries which then are
used to calculate a fin efficiency and Ts value. In addition, the mathematical model shows the
weight of the fins used, which will play into the final cost of the product.
In the table shown, the actual geometry used for the fins shows a theoretical temperature of
over 46°C. Various other geometries were entered to the mathematical model (see Appendix).
Although many showed a higher fin efficiency at smaller fin lengths, tests showed that the tops
of these pins were becoming too hot, showing that more material could be added on. In
addition, using thicker pins showed a lower temperature as well as a higher efficiency, but the
stock material for such geometries was unavailable to the team, the costs were higher, and
manufacturing as many pins on a lathe was not allowed because of the high demand for
machines in the shop.
13. 13
Table 6. Fin Forced Convection Mathematical Model
The third and final mathematical model to be considered assumes the use of fins, which applies
to this group’s design. This analysis is conducted to understand the effect of the 3-minute
heating period on the device, and whether the predicted steady state temperature from the fin
analysis will be reached by the device. Transient analysis is found by assuming a lumped system
model, as shown in Equation 18.
(18)
In this situation, the qloss is set to zero due to the small amounts of energy lost by natural
convection as the device is heating up. The equivalent heat capacity of the device is given by
(mcP)equiv, and is found by Equation 19.
(19)
Equation 18 can be solved for TH. The cooling period after the 3-minute mark changes the
equation, and is represented by Equation 20.
(20)
Fin efficiency Fin S A Fin CS A
η fin m h As k Ac L q
0.96743882 10.62771941 36.7576514 0.000598473 3.16692E-05 0.03 20
(Taken from forced) 0.000630143
38 Pins
Aluminum Properties Plate Fins
ρ 2702 kg/m^3 l 0.06476 0.003175 r
N 38 w 0.07031 0.03 h
V 3.61029E-05 m^3 Aplate 0.004553276
cp 1013 J/(kg-K)
k 205 W/(m-K)
α 2.25E-05 m^2/s
Cost 1.47 $/kg Mass fins 0.097550057
Mass plate 0.038754295
Weight Fins
0.097550057 kg Area Fins 0.023945419
0.143398584 $ Cost
K C
Ts 319.6292913 46.47929131
14. 14
The above differential equation is solved for T, which is the temperature of the device
(Equation 21). This equation can then be algebraically manipulated to give tss, which is the
amount of time the device will take after the 3-minute mark to reach its predicted steady state
temperature (Tss) fromthe fin analysis (Equation 22).
(21)
finsfinplate
heater
H
finsfinplate
equivp
ss
AAh
q
TTAAh
mC
t
2.0
ln (22)
Using the predicted Tss value from the fin analysis, it was found that the steady state would be
reached from the fins after approximately 5 minutes.
Table 7. Steady State Results from Transient Analysis
tss final 305.2655 (s) 5.087759 (min)
Testing and Verification
Before making any alterations to the plate or doing any designs, it was necessary for the team
to run initial tests to understand the range of temperatures currently at work. Initial tests with
the plate resting on the table and no alterations done to it show value ranges around
approximately 115°C after 3 minutes, and 150°C after 6 minutes when the fan is not run at all.
With the fan running after 3 minutes, the values are significantly lower.
Table 8. Initial Plate Tests without Box Fan
Without Fan (°C)
Trial 3 Min 6 Min
1 125.9 154.1
2 130 174
3 107 158
4 115.5 144.4
5 113.9 150.4
Table 9. Initial Plate Tests with Box Fan
With Fan
Trial 3 Min 6 Min
1 114 66.5
2 111.4 65.7
15. 15
Initial tests were run using fins of 40 mm length, which is 10 mm longer than the final design
used. The group saw that without the fan, the top few millimeters of the fins were at room
temperature or below. This indicated to the group that the mathematical model must be
consulted again to find a shorter length in which as much of the material applied as possible
heats up.
With the two computer fans, the group believed theoretically it would work best if a fan was
placed on top pointed upwards from the fans. However, the direct air blowing back into the
center may have a positive impact on the thermocouple reading. To test these questions as
well as many other mini fan orientations, the group kept the positioning of the plate and the fin
array as a constant.
Table 10. Prototype Testing with Various Orientations
Temperature
Test Type 3 min 6 min
Plates Only - Test 1 110°C 64.0°C
Plates Only - Test 2 114.9°C 64.8°C
Plates Only - Test 3 110.5°C 61.7°C
Box Fan Only 49°C 37.4°C
Mini Fan Facing Up Only 53°C 36.6°C
Mini Fan Facing Down Only - 35.7°C
Both Mini Fans w/ One Facing Down - 36°C
Elevated 6 inches w/ Mini Fan Facing Down 52.7°C 35.2°C
The lowest temperature we were able to achieve was 34.7°C. This was one mini fan pointed
downwards with the pin fin array. The next lowest temperature we were able to achieve was
with the mini fan facing downwards when the plate was elevated. In many of these situations,
it was seen that the batteries were failing on the fans before the end of the test, and results
were not reliable. The increased cost added by the fans and supporting batteries would
increase out estimated price by about 10x its original value, and add over approximately 44.2
grams per fan used. In addition, more weight would be needed to suspend the fans at a 7-inch
height where the box fan showed the highest velocity. Seeing the small difference made by
adding in the computer fans, the group decided the disadvantages in weight and cost were not
worth the small change in degrees. The device could still perform better by lowering the pin
size.
In adjusting the pins, more tests were conducted between various length sizes. Due to a limited
amount of material, the group was unable to use smaller increments of testing, and had to rely
on the mathematical model to verify lengths of pins. It was also seen using fewer pins than the
amount the group was able to fit led to higher temperature readings as well.
16. 16
Table 11. Testing Results with Various Pin Lengths
Fin Length/Quantity Temperature @ 6 minutes
40 mm, 31 pins 38.9°C
40 mm, 38 pins 38.4°C
35 mm, 38 pins 37.3°C
30 mm, 38 pins 36.9°C
25 mm, 38 pins 38.0°C
The next tests performed were to compare the temperature readings done at the regular 4
inches to the readings done at where the velocity was highest for the box fan. All orientations
at this given height showed readings at the lowest of position settings, around 32-34°C.
Final testing was done to determine whether it’s better to have the air flow from the box fan
flowing through the staggered geometry, or parallel with the straight lines.
Table 12. Testing Results with Different Fin Arrangements
Orientation
Temperature @ 6
Minutes
Parallel, straight flow 32.9°C
Staggered, wavy flow 35.1°C
With the competition day approaching, the team was satisfied with an operating temperature
only 10°C above room temperature, and extremely low weights and costs.
In comparison to the mathematical models, the team saw fairly large discrepancies. With
natural convection, the plate was never allowed to heat for a long enough time period to reach
that temperature. When looking at the natural convection, the plate is estimated to reach
around 230°C, while at the 6-minute mark it only reaches a maximum of 174°C from tests.
Forced convection values for both without fins and with fins show a similar trend of being
significantly higher than values in test results. Without the fins, the expected temperature is to
be 86.6°C, while the tested values are slightly over 20°C less than that value. With fins, the
tested value comes slightly closer, approximately 15°C lower than the predicted value of 47°C
from the mathematical model.
With mathematical models, there are many explanations for increased values when compared
to testing. Air properties and are taken to be ideal, and a room temperature is estimated using
the thermocouple. While the room temperature can vary day by day, the model sticks with one
average room temperature. This throws off the fluid property values. The aluminum is also
considered to be a pure aluminum. If taken from the machine shop, the group has no way of
knowing whether it is a 6061 alloy, or pure aluminum. By assuming the wrong kind, the
properties of the plate and fins change immediately. In addition, the aluminum may have
17. 17
impurities in it. The addition of fins is not perfect, where there may be many gaps between the
two materials as well as different shapes and sizes of the fins. The high temperature adhesive
may also absorb and hold plenty of heat, which is not considered in the analysis. Fan power
may vary from box fan to box fan, and other drafts within the test setting room are also
ignored. There is, however, a similar trend with the pattern of experimental vs. theoretical
values. When the theoretical decreases significantly, the experimental value does the same,
showing that trends are recognized with the mathematical model.
Due to the various calculations, uncertainty errors needed to be taken into account. The
uncertainty values calculated showed a smaller range than the actual variations between
testing and theoretical values. The same method used in the Error Estimation Experiment was
used in the derivation and calculation of the uncertainty values. The equations are as follows,
where dq is equal to 0.5 watts and q is equal to 20 watts.
Uncertainty Calculations
𝑑𝑇𝑠 = 𝑇𝑠 ∗ (
𝑑𝑞
𝑞
) (23)
𝑑𝑡𝑠𝑠 = 𝑡𝑠𝑠 ∗ (
𝑑𝑞
𝑞
) (24)
Table 13. Uncertainty Error Values
Uncertainty Analysis
tss final 7.631 s
Ts (w=.005) 9.443 K
Ts(w=.01) 9.440 K
Ts(final design) 7.991 K
Recommendations / Conclusions –
The team’s final project placed 19th out of 40 teams, many of which used various versions of the
design concepts discussed earlier in this report. For the three parameters, the placings and
values are as follows:
1) Temperature – 31.2°C, 28th
place
2) Weight– 169.2 grams,3rd
place
3) Cost - $2.60 – 15th
place
The pin fin array design was manufactured based on the idea of using an axial air flow. The
team overlooked the idea that air flows in different directions would hinder the performance of
each fan. However, the pin fins were already manufactured when the team was close to the
competition day, and switching to a rectangular fin array would lead to a risk. For future
designs, the team would consider using the rectangular fins if only the box fan were being used.
Other recommendations for the pin fin array would include thicker pins at a fewer number, at a
18. 18
shorter length. From the mathematical model, these thicker pins would be able to draw more
heat away from the plate itself. In addition, the pins could have been manufactured with a
tighter tolerance and cut with smoother finishes. The screws used that went into the balsa
would could have been smaller. If cost were not as important, advanced heat sinks for
computers utilize a combination of copper and aluminum. Hollow copper tubing of the right
diameter could be tested with axial flow. The hollow piping could almost double the surface
area increased by pins. Orientations between staggered pins and grid-like square patterns
could also be tested.
19. 19
References
1. C.J. Paul, ME 412 Enhancement of Electronic Cooling. Michigan State University, 2016.
2. C.J. Paul, ME 412 Forced Convection Analysis. Michigan State University, 2016.
3. C.J. Paul, ME 412 Natural Convection Analysis. Michigan State University, 2016.
4. C.J. Paul, ME 412 Transient Analysis. Michigan State University, 2016.
5. "Cooling101: The Basicsof Heat Transfer." Koolance.Koolance,Inc.Web.02 May 2016.
6. "Heatsink 101." Geek Easy Computers. Geek Easy Computers, 29 May 2013. Web. 02 May 2016.
7. Incropera,FrankP., andDavidP.DeWitt. Introduction to HeatTransfer.6thed.JohnWiley&Sons,
New York. Print. 2011.
8. "Replacement70mmTX3 Dual Ball BearingCPU CoolerFan." StarTech.com.StarTech.com.Web.
02 May 2016.
21. 21
Appendix B – Computer Fan Data
Performance
Air Flow Rate 21.33 CFM
Fan RPM 3500
Noise Level 33 dBA
Power
Input Current 0.25
Input Voltage 12 DC
Power Consumption 2.16W
Physical Characteristics
Color Black
Enclosure Type Plastic
Product Height 2.8 in [70 mm]
Product Length 2.8 in [70 mm]
Product Weight 1.2 oz [35 g]
Product Width 0.4 in [10 mm]
Appendix C – Air Fluid Properties
Appendix D – Properties of Materials Used
Balsa Wood Properties
Compressive Strength 7 Mpa
Density 0.13 g/cm^3
SpecificHeatCapacity 1700 J/kg-K
Aluminum Properties
ρ 2702 kg/m^3
N 38
V 0 m^3
cp 1013 J/(kg-K)
k 205 W/(m-K)
α 2.25E-05 m^2/s
Cost 1.47 $/kg
T (K)
μ
(Pa-s)
k
(W/m-K)
Pr
Cp
(kJ/kg-K)
ν
(m2
/s)
α
(m2
/s)
β
(1/K)
300.00 1.842E-05 2.58E-02 0.707 1.007 1.515E-05 2.229E-05 0.00333333
22. 22
Arctic Silver Adhesive Properties
Form Viscous
Color Silver
MeltingPoint >999°C
BoilingPoint >204°C
Density 2.28 g/cm^3
