1. 1
Po-Chun Kang
PORTFOLIO
MASTER OF SCIENCE - MECHANICAL ENGINEERING
School of Engineering for Matter, Transport, and Energy
May 2016
1207901496
Pkang4@asu.edu

2. 2
MAE589: Heat Transfer Project
EFFECTIVENESS OF FIN ON A CPU
Akshay Deepak Bhatia
Ishan Pahwa
Karthik Kannan
Po-Chun Kang
Arizona State University
May 1, 2015

3. 3
EFFECTIVENESS OF FIN ON A CPU
Akshay Deepak Bhatia
Department of Mechanical and Aerospace Engineering
School of Engineering for Matter, Transport & Energy
Tempe, Arizona
Ishan Pahwa
Department of Mechanical and Aerospace Engineering
School of Engineering for Matter, Transport & Energy
Tempe, Arizona
Karthik Kannan
Department of Mechanical and Aerospace Engineering
School of Engineering for Matter, Transport & Energy
Tempe, Arizona
Po-Chun Kang
Department of Mechanical and Aerospace Engineering
School of Engineering for Matter, Transport & Energy
Tempe, Arizona
ABSTRACT
The following paper introduces a concept of rotating air-
cooled heat exchanger for the purpose of cooling a Central Pro-
cessing Unit of a computer. The model is basically an amalga-
mation of a traditional heat exchanger and a fan that is combined
into one in an attempt to develop a more efficient heat exchanger
unit. The project was focused on designing and analysis of dif-
ferent parameters of fins including choosing different materials
so as to get a most efficient fin shape and a structure which can
be used over CPUs to dissipate heat. In addition, computational
simulation was carried out to fully understand the performance
characteristics of each of the key designaspects.
NOMENCLATURE
u Components of velocity [m/s]
ρ Density [kg/m3
]
P Pressure [kPa]
µ Dynamic viscosity [kg/m· s]
k Thermal Conductivity [W/m·K]
h Heat Transfer Coefficient [W/m2
· K]
T Temperature [K]
Bi Biot Number
Lc Characteristic length [m]
Nu Nusselt Number
Re Reynolds Number
Pr Prandtl Number
INTRODUCTION
In the old days, choosing a computer was easy: you bought
the one with the fastest processor you could afford. And you
knew which one was fastest by its numerical clock-speed rat-
ing but know with the advancement in PC computation we need
processors capable enough to do high performance computing,
including 4K video editing, high end games and complex de-
signing. As everything today virtually depends upon computers
we need to have faster processors capable enough to meet the
demands of the present and the future. Fig. 1 shows how the
CPU clock speeds have increased drastically over the period of
4 decades. Higher clock speeds directly relates to greater power
generation in the chip, resulting in higher core CPU tempera-
tures. Therefore, it is necessary to have an efficient cooling sys-
tem, which dissipates the heat from the CPU optimally and at
a fast rate to avoid damage to the electronics owing to massive
heat.
The principle objective of a rotating air-cooled heat ex-
changer is to dissipate the heat away from the CPU. Instead of
the conventional heat sink with a fan, the rotating air-cooled heat
sink is designed to greatly increase the heat transfer efficiency.
In the traditional cooler, the logjam of heat transfer is that the
boundary layer of stagnant air is not heavily relied by the air-
flow, which is made by the fan. Nonetheless, in this improved
rotating cooler, heat is more efficiently transferred from the sta-
tionary basement to its surrounding. Although this innovative
device has not been used widely, this concept has been demon-
strated through several experiments [2] and showed promising
results reaching 10 times reduction in the boundary layer thick-

4. 4
A
−
σ
i
V
Lc =
s
(2)
FIGURE 1. EVOLUTION OF CPU CLOCK SPEEDS OVER TIME
[1].
ness at a speed of a few thousand rpm [3]. Based on this tech-
nique, it can greatly solve the heat exchanger fouling problem.
To achieve similar effect, the results obtained from varying fin
shapes, number of fins, dimension of fins, and speed of rotation
The conjugate heat transfer problem being solved in the
present work is done numerically and is as follows. The turbulent
Navier-Stokes and energy equations are solved in numerically by
a finite-volume method using the commercial flow solver AN-
SYS. In order to simulate the thermal and turbulent flow fields, it
is required to give certain assumptions below which are used to
simulate the stationary as well as the rotating air-cooled heat ex-
changer: (1) incompressible fluid, (2) constant fluid properties,
(3) uniform heat flux, (4) negligible radiative heat transfer, and
(5) turbulent flow.
Following the aforementioned assumptions, it is required to
apply the momentum (Eqn. (3)), continuity (Eqn. (4)) and the en-
ergy equation (Eqn. (5)) so as to describe the heat transfer phe-
nomenon.
were comparatively studied in this present work. Moreover, op-
timizing the rotating heat sink by means of optimizing parameter
variation was also studied.
(ρu) = + µ
∂x ∂x ∂x
+
∂x ∂x
−ρ u (3)
MATHEMATICAL MODEL
One of the major property in the rotating heat sink is its ther-
mal performance. A typical way to easily account for the thermal
performance is by making use of the thermal resistance, which is
the temperature difference between the heat sink surface and the
∂ u
∂ x
= 0 (4)
air above it divided by the total heat dissipate away. In this way ∂T ∂ ..
µl
µt
.
∂T
.
one can compare the difference between the new design and for-
mer one.
Now, the lumped system analysis is a really useful tool to
derive the total thermal resistance. Firstly, the Biot number (Bi)
(ρu)
∂x
=
∂x
+
σl t ∂x
(5)
has to be determined, which is a dimensionless parameter of the
system. This parameter (shown in Eqn. (1)) is the ratio of the
internal resistance of a body to heat conduction, to its external
∂t
+
∂xi
=
∂x σ
·
∂ x
ε j (6)
resistance to heat convection. This will help determine if the
lumped model is applicable or not. If the Biot number is less
than 0.1, it means that the variation of the temperature is small
enough for the lumped system to work. The Biot number must
generally be less than 0.1 in order to proved a more accurate
approximation. Even if this number is greater than 0.1, we still
can use it but the accuracy will generally decrease.
Additionally, the k−ε model (Eqn. (6)) is used as a turbu-
lence closure model to simulate the statistical flow characteris-
tics, whichis predominant inthe near region of the heat sink.
THEORETICAL ANALYSIS
To compute the heat transfer from the heat sink effectively, it
is necessary to have the proper heat transfer coefficient based on
the problem in hand. There are various methods of calculating
the heat transfer coefficient for different modes of heat transfer,
(1) for different given flow regimes, and other such thermodynamic
𝜕𝑢
𝜕𝑥
(𝜌𝑢) = −
𝜕𝑝
𝜕𝑥
+
𝜕
𝜕𝑥
[𝜇 (
𝜕𝑢
𝜕𝑥
+
𝜕𝑢
𝜕𝑥
) − 𝜌𝑢]
𝐵𝑖 =
ℎ𝐿 𝑐
𝑏
𝜕𝑢
𝜕𝑥
= 0
( 𝜌𝑢)
𝜕𝑇
𝜕𝑥
=
𝜕
𝜕𝑥
[(
𝜇 𝑙
𝜎𝑙
+
𝜇 𝑡
𝜎𝑡
)
𝜕𝑇
𝜕𝑥
]
𝜕(𝜌𝜀)
𝜕𝑡
+
𝜕(𝜌𝜀𝑢)
𝜕𝑥 𝑖
=
𝜕
𝜕𝑥 𝑖
[
𝜇 𝑡
𝜎 𝜖
.
𝜕𝜀
𝜕𝑥 𝑗
] + 𝑐1𝜀
𝜀
𝑘
2𝜇 𝑡 𝐸𝑖𝑗 𝐸𝑖𝑗 − 𝑐2𝜀 𝜌
𝜀2
𝑘
(6)

5. 5
conditions. The heat transfer coefficient was calculated by the
following procedure.
Initially, the thermodynamic properties of air is obtained
from EES (Engineering Equation Solver) at a temperature, Tavg.
This temperature is the arithmetic average between the surface
temperature (Ts) of the heat sink, and the ambient temperature
(T∞) of air. The thermodynamic properties of interest are Prandtl
number, Pr and the thermal conductivity, k. The Reynolds num-
ber of the flow is given by:
Re =
ρ𝑣∞ 𝐿 𝑐
μ (7)
FIGURE 2. FLOW FIELD AROUND SANDIA COOLER [2].
axis of the heat sink. Both edges of the fins were rounded using
where, the characteristic length, Lc is a length scale based
on the computational domain, as described in the following sec-
tion. The resulting Reynolds number indicates that the flow is
turbulent for the current setup and hence the Nusselt number of
the flow can be estimated by,
Nu = 0.0308Re0.8
Pr1/3
(8)
Following which, the heat transfer coefficient for the given
conditions can be found using,
fillets with a fillet radius of 0.01 inches. The thickness of the fins
was set to a constant 0.1 inches throughout the fin, excluding the
fillet.
k Nu
h =
Lc
(9)
FIGURE 3. ISOMETRIC VIEW OF BASE HEATSINK MODEL
This approach is used on all the variations performed in the
present work, for instance, for a given average temperature of
65◦
C, the thermal conductivity is 237.8W/m · K, and Prandtl
number is 0.708. For a given free-stream velocity of 0.2 m/s,
the heat transfer coefficient turns out to be 253.29W/m2 · K
DESIGN OF HEAT SINK MODEL
The key to the design is the heat-sink impeller, which con-
sists of a disc-shaped base populated with fins on its top surface.
The impeller acts as a hybrid of a conventional finned metal heat
sink and an attached fan, for the purposes of the evaluation. A
base model was designed using the Sandia cooler (Fig. 2) as a
reference, upon which all further variations were made. Figures
[3-5] show the base model in its various views.
The diameter of the base circle of the model was 4 inches,
following the design of the aforementioned Sandia cooler. The
shapes of the fins were chosen to be intersecting arcs in all of
the model variations including the base model. The inner edge
of the fins were at a distance of 2 inches away from the centroid
The height of the fin from the point of contact to the base
of the model to the tip of the fin was taken as 1.18 inches. The
number of such fins is30.
FIGURE 4. TOP VIEW OF BASE HEATSINK MODEL
h =
𝑘𝑁𝑢
𝐿 𝑐

6. FIGURE 5. FRONT VIEW OF BASE HEATSINK MODEL
This model, referred to as the base model, will be considered
for the stationary analysis case, and variations will be made to
this model. The first variation in model design parameter is the
number of fins, which was varied from 30 to 40 and finally, 50.
This variation will help characterize the effect of the number of
fins on the overall heat transfer.
The second variation in model design parameter is the height
of the fins. The height was decreased from the base value of 1.18
inches to 1 inch and finally, 0.95 inches. The reasoning for this
choice is that experiments conducted [2] on the Sandia cooler by
Sandia National Laboratories used these same values.
The final design parameter variation is the speed of rotation
of the rotating heat sink. The speed of rotation was varied from
1000 rpm (rotations per minute), to 2000 rpm and finally, 3000
rpm. The base of the heat sink is in contact with an extrusion
of square cross section with unit side length and height as 0.1
inches. This part is used to model the contact between the heat
sink and the CPU, and also to specify the volumetric heat gener-
ation and uniform heat flux from theCPU.
Choice of material of the heat sink was researched on, with
the prime candidates being copper and aluminum. The more pop-
ular choice in the computer hardware market is aluminum, owing
to cheaper costs and comparable performance in comparison to
copper. Therefore, aluminum was chosen as the material of the
heat sink.
Design modeling of the base model and all variations to it
was performed using PTC Creo Parametric Student Edition.
PROBLEM SETUP
The conjugate heat transfer problem is solved numerically
using the commercial flow solver ANSYS Fluent, and the de-
signed heat sink was setup in the solver as described below.
The heat sink is placed in a rectangular domain of length
40 inches, width 20 inches and height 10 inches, at a distance
10 inches from one vertical face of the domain. This face is the
designated velocity-inlet boundary, from where the air flow will
FIGURE 6. COMPUTATIONAL SETUP OF PROBLEM DOMAIN
initiate. The outlet face is on the opposite side at a distance of 30
inches from the downstream end of the heat sink.
Meshing the domain and the heat sink is an important step in
the solution procedure of the numerical simulation, and required
special treatment in the case of rotation. The heat sink model
and the rectangular domain were meshed separately without any
regard for conformity between the two meshes. This allowed to
take advantage of the ANSYS moving reference frame model [4]
to simulate the rotation of the heat sink. The side walls of the
domain were maintained as no-slip walls with adiabatic thermal
boundary condition. The reason for this setup is to mimic the
operating conditions within a realistic computer housing.
The geometric part which is meant to act as the contact be-
tween the heat sink and the heated surface (CPU), as described in
earlier sections, carries the thermal load application to the prob-
lem. The contact volume is set to contain a volumetric heat
generation based on the thermal design power (TDP) rating of
a modern Intel Core i7 processor [5] and the geometric volume
of the contact. Uniform heat flux boundary condition on the heat
sink is applied based on these values.
The heat transfer modeling was based on the condition that
the heat sink will start to rotate once the CPU heated surface
reaches a temperature of 65◦
C. This closely follows the more
modern after-market coolers available on the market, wherein
the fans do not start rotating until a threshold temperature is at-
tained. This concept was applied to the rotating heat sink model,
with the initial condition for the heated CPU surface being the
aforementioned 65◦C.
The solver was set to perform a transient solve for the tur-
bulent Navier-Stokes equation, using the k − ε closure model,
while also including the energy equation. All solution controls
4

7. 5
and methods were chosen appropriately to ensure the best trade-
off between accuracy and solution convergence.
RESULTS AND DISCUSSION
The problem was initially solved for a stationary heat sink
model for a time of 10 seconds. The temperature distribution
within the heat sink is shown in Fig. 7 as contours on the heat
sink surface. It should be recalled that the stationary heat sink
was designed with 30 fins, each with a height of 1.18 inches. This
is reference case with which all variations studied are compared.
FIGURE 7. TEMPERATURE DISTRIBUTION FOR STATIONARY
HEAT SINK
In order to make comparisons that can be used in drawing
conclusions, and also captures the essence of the problem objec-
tive, it was chosen that point of interest is the surface of con-
tact between the heat sink and the CPU, which boils down to a
squared surface shape. Further simplification in solution anal-
FIGURE 8. EFFECT OF VARIATION OF NUMBER OF FINS
increasing the number of fins does not impact the heat transfer as
dramatically, as the maximum temperature difference at the end
of simulation reaching 2.2◦
C. There may be some potential lim-
itation in terms of insufficient mesh resolution for the solver to
resolve the flow field in the case of the higher fin count models.
TABLE 1. OVERALL HEAT TRANSFER
Model Variation Total Heat Transfer (W)
Stationary Model - 202.69
- 225.43
ysis was done in the sense that instead of performing compar-
isons between entire surfaces, a point on the surface was chosen.
This point is the geometric centroid of the square-shaped sur-
face, which would be the result of intersection of the diagonals
of the square. In a realistic scenario, this would also be the point
of maximum heat generation owing to the location of the chip
within the CPU die.
The first parameter variation to be studied is the effect of
varying the number of fins on the circular base of the model.
This was done while keeping the other parameter variations con-
stant, similar to the stationary model. The evolution of tempera-
Rotating Model
40 fins 229.90
50 fins 231.20
1.00 ” fin height 216.07
0.95 ” fin height 213.88
2000 rpm 233.17
3000 rpm 239.02
ture over time at the point of interest is shown in Fig. 8, plotted
along with the stationary model’s temperature evolution in red.
It is noted that the rotating heat sink does indeed perform better
than the stationary heat sink, resulting in a temperature differ-
ence of about 5◦
C at the end time of the simulation. However,
The second design parameter variation that was studied is
the effect of varying the height of the fins. The evolution of
temperature over time at the point of interest is shown in Fig. 9,
plotted along with the stationary model’s temperature evolution
in red. The height of the fins were only decreased from the

8. 6
and methods were chosen appropriately to ensure the best trade-
off between accuracy and solution convergence.
RESULTS AND DISCUSSION
The problem was initially solved for a stationary heat sink
model for a time of 10 seconds. The temperature distribution
within the heat sink is shown in Fig. 7 as contours on the heat
sink surface. It should be recalled that the stationary heat sink
was designed with 30 fins, each with a height of 1.18 inches. This
is reference case with which all variations studied are compared.
FIGURE 9. EFFECT OF VARIATION OF FIN HEIGHT
base model, similar to experiments conducted by Sandia Na-
tional Laboratories, as discussed earlier. It is noted that the heat
transfer is related directly to the height of the fins, as expected
with the end temperatures getting closer to that of the reference
stationary model as the height of the fins were decreased. Further
studies with increasing fin heights need to be performed to take
this further.
FIGURE 10. EFFECT OF VARIATION OF SPEED OF ROTATION
The final design parameter variation studied is the effect of
varying the speed of rotation of the rotating heat sink. This
case showed the most promising effects with the final
temperature dropping lower than all previous cases with increase in
speed of rotation of the heat sink, with the heat sink rotating at 3000
rpm reducing the CPU contact’s temperature down to about 45◦
C at
the end of 10 seconds. The overall heat transfer rate for these cases
indicate the same conclusions as the final temperature, as shown in
Table 1.
CONCLUSIONS
The present work attempts to develop a new and innova- tive
rotating air-cooled heat exchanger. The conceptualized sys- tem
takes inspiration from current technologies like the San- dia
Cooler. Multiple assumptions are made to simplify the de- vices
design while still allowing for the fundamental theory to be tested.
By doing the ANSYS simulation some results were very clear. The
heat sink is much more efficient in dissipating heat when it is
rotating as compared to when it is stationary. The effect of varying
number of fins is marginal, if present at all. Further high fidelity
simulations are recommended to establish a more dependable
conclusion for this case.
Decreasing the height resulted in lower heat transfer rate, as
expected. Further simulations with increased fin heights are sug-
gested. However, it should be noted that in reality, fin heights are
constrained by limited space within a computer housing. The ef-
fect of varying speed of rotation showed increased heat transfer
rates. This is extremely promising and shows how higher heat
transfer rates can be attained. However, even this parameter is
limited in the real-world as higher speeds of rotation means in-
creased power consumption and more noise. Using the lessons
learned from this project, it will be possible to create a more ef-
ficient heat sink by performing optimization on the parameters
studied.
REFERENCES
[1] Laboratories, S. N., 2010. The Sandia Cooler: A fundamen- tal
breakthrough in heat transfer technology for microelec- tronics.
[2] Johnson, T. A., e. a., 2013. Development of the Sandia Cooler.
Unlimited Release SAND2013-10712, Sandia Na- tional
Laboratories, Albuquerque, NM, December.
[3] Yang, Y. T., Lin, S. C., Wang, Y. H., and Hsu, J. C., 2013.
“Numerical Simulation and Optimization of Impingement
Cooling for Rotating and Stationary Pin-Fin Heat Sink”. In-
ternational Journal of Heat and Fluid Flow, 54, December, pp.
383–393.
[4] ANSYS, I., 2010. Using Moving Reference Frames and Sliding
Meshes.
[5] Huck, S., 2011. Measuring Processor Power: TDP vs. ACP.
White Paper 1.1, Intel Corporation, April.

9. 1
MAE585: Solar Thermal Engineering Project
OPTIMIZATION OF A SOLAR STILL
Evvan Morton
James Sandrolini
Mohammed Adnaan Hussain
Mariana Lopez
Mohammed Safee Rehman
Po-Chun Kang
Arizona State University
December 4, 2015

10. 2
OPTIMIZATION OF A SOLAR STILL
Evvan Morton Arizona
State University Tempe,
Arizona, USA
Po-Chun Kang Arizona
State University Tempe,
Arizona, USA
Mohammed Adnaan Hussain
Arizona State University
Tempe, Arizona, USA
Mariana Lopez Arizona
State University Tempe,
Arizona, USA
James Sandrolini
Arizona State University
Tempe, Arizona, USA
Mohammed Safee Rehman
Arizona State University
Tempe, Arizona, USA
ABSTRACT
The objective of this project is to optimize a simple, single
sloped solar still by changing the degree of slope. Theoretical
calculations and results were derived using Engineering Equa-
tions Solver (EES) software. Three slope degrees were tested in
the experimental analysis: 15, 25, and 35. Three solar stills were
constructed for each of the three slopes. Radiation data was col-
lected and used to calculate experimental results. No clean water
was produced from the stills, however the 35 sloped still received
the most solar radiation. Future work addresses measures to im-
prove the solar still design
NOMENCLATURE
δ declination angle
n solar day
φ latitude
β slope
ω hour angle
γ surface azimuth
τ transmittance
α solar altitude angle
S absorbed solar radiation
I radiation intensity
F collector efficiency factor
Cp specific heat
θz zenith angle
nair refractive index
rpar parallel component - reflectance
rper perpendicular component - reflectance
INTRODUCTION
Solar stills are a simple and low cost way to provide potable
water by using the suns thermal energy. The concept of evap-
orating unclean water and condensing it for drinking was first
thought of by Aristotle in the fourth century BC [1]. Besides
potable water, solar stills are also used for irrigation, recovery of
salt, and alcohol production [1]. Solar stills improve health stan-
dards by removing contamination from water used for drinking,
cooking, washing, and bathing. In developing countries and rural
areas where clean water can be scarce, solar stills provide imme-
diate access to clean water. This decreases travel time for people
in areas with only one source of clean water and also reduces
dependence on rainfall [1].
There are various ways to create a solar still. The basic de-
sign of a solar still includes a black basin to hold the water being
distilled covered by a transparent sheet of glass or plastic [2].
Figure 1 shows an example of a basic solar still [1]. The water to
be distilled lies in the basin of the still. As the sun hits the trans-
parent cover, the water temperature rises, creating water vapor.
This vapor travels up to the transparent cover were it is collected

11. 3
2
2
−
δ = 23.45 ∗ sin 360 ∗ (284 +n)
365
(1)
By substituting all the parameter we know, so we can get the
angle of incidence on the surface.
FIGURE 1. Operation of a Solar Still
in droplets. These droplets then travel down the slope of the
transparent cover into an output basin of clean water. There are
various designs of solar stills including single sloped, spherical,
cos(θ1 ) = sin(δ ) ∗ sin(φ) ∗ cos(β ) −sin(δ )
∗ cos(φ) ∗ sin(β ) ∗ cos(γ) +cos(δ ) ∗ cos(φ)
∗ cos(β ) ∗ cos(ω) +cos(δ ) ∗ sin(φ) ∗ sin(β )
∗ cos(γ) ∗ cos(ω) +cos(δ ) ∗ sin(β ) ∗ sin(γ)
∗ sin(ω)
(2)
pyramid, hemispherical, double basin, tubular, and concentrating
solar stills [2,3].
The objective of this project is to optimize a simple, single
sloped solar still by changing the degree of slope. Theoretical
calculations and results were derived using Engineering Equa-
tions Solver (EES) software. Three slope degrees were tested
in the experimental analysis: 15, 25, and 35. The following sec-
tions explain the theoretical and experimental results as well as
a comparison of the two analyses. This paper concludes with
troubleshooting, discussion of results, and plans for future work
THEORETICAL MODEL
We will use the zenith angle to calculate the Rb , which will
be used in the further.
cos(θz) = cos(φ) ∗ cos(δ ) ∗ cos(ω) +sin(φ) ∗ sin(δ ) (3)
Besides, we are using the equation which is derived by the
Fresnel for the reflection of unpolarized radiation on passing
from the air with the refractive index NAIR to glass refractive
index nglass . The angles θ1 and θ2 are related to the indices of
refraction by Snells law.
nair sin(θ1 ) = nglass sin(θ2 ) (4)
tan(θ2 −θ1)
rpar =
tan(θ
(5)
+θ1 )
sin(θ2 −θ1)
rper =
sin(θ
(6)
+θ1 )
FIGURE 2.
Within the solar still energy is transferred from the glass
cover into basin by solar radiation, as shown in Fig. 1. So we
are going to get the angle of incidence of beam radiation on the
surface, θ1 . However, we have to know the declination angle in
advance:
Radiation absorbed by a transparent cover
In order to get the total transmittance of our single glass,
we have to consider both the effect due to absorption and reflec-
tion. The equation of transmittance due to the effect cause by
absorption in a partially transparent medium has been described
as following
KL
τa = exp
cos(θ )
(7)
2
𝑟𝑝𝑒𝑟 =
sin⁡( 𝜗2 − 𝜗1)
sin⁡( 𝜗2 + 𝜗1)
𝑟𝑝𝑎𝑟 =
𝑡𝑎𝑛(𝜗2 − 𝜗1)
𝑡𝑎𝑛(𝜗2 + 𝜗1)
𝜏 𝑎 = exp⁡(
−𝐾𝐿
𝑐𝑜𝑠𝜗2
)

12. 4
a
10−10
θ 6
θ
The transmittance of initially unpolarized radiation is the av-
erage of the two components,
- Water surface is parallel to the glass cover
- either the side or the bottom of the basin is adiabatic, so
there is no heat loss under the glass cover
- there is no water leaking from the still
1 1 −rpar 1 −rper
(8τr =
2 1 +rpar
+
1 +rper - the amount of water lost through evaporation is trivial com-
pared to the amount of the water
Thus, the overall transmittance for the glass is given by mul-
tiplying τr and τr
τ = τa ∗ τr (9)
Angular dependence of solar absorptance
If we assume the absorptance of the plate at normal inci-
dence is 0.9 as a flat black surface, so we can calculate the α by
following formula:
= 1 −1.5879 ∗ 10−3
θ1 +2.7314 ∗ 10−4
θ 2
−2.3026∗
- Alternatively, the mass of the water is considered to be
constant at all the time
- the diffuse radiation is ignored, therefore we are only con-
sidering the absorbed solar radiation from the beam directly
Eliminating Q from the Eqs.(13) and (14), then we can cal-
culate the temperature of the water, Tw.
DESIGN
When considering the design of the boxes, cost was the main
focus. For the boxes that would hold the water, the experimenters
decided to use a Styrofoam cooler that was readily available, and
cut the boxes at the predetermined angles of 15, 25 and 35 de-
an
10−5
θ 3 −7 4
1
−8 5 (10)
grees. Then, attach glass covers to each box using an adhesive.
1 +9.0244 ∗ 10 θ1 −1.8000 ∗ 10 θ1 +1.7734∗ In order to get water both in an out of the boxes, the exper-
1 −6.9937 ∗ 10
Thus, the absorbed solar radiation is given by:
−13 7
1
imenters would need to add inlet and outlet holes with snuggly
fitting pipes to run water in and out of each box. Finally, in or-
der to guide the water droplets from the glass cover to the outlet
hole, the experiments would add a rail that would be adhered to
the box to carry the water.
The Styrofoam coolers were not available at local grocery
where
S = It ∗ Rb ∗ (τ α ) (11) stores, so the experimenters bought them from a local conve-
nience store, for around seven dollar each. The coolers had inside
dimensions of 12 and 9 and included top pieces.
Rb = cos(θ1 )/cos(θz) (12)
Energy balance equations
The energy balance equations for the water inside the basin
can be written as follows:
The heat gain form the solar radiation
Q = A ∗ F ∗ S (13)
The heat absorbed by the water
Q = m∗ Cp ∗ (Tw −Ti) (14)
In order to apply the energy balance equations above prop-
erly, we have to make the following assumptions:
FIGURE 3. Glass cover attached to styrofoam box using hot glue
𝜏 𝑟 =
1
2
(
1 − 𝑟𝑝𝑎𝑟
1 + 𝑟𝑝𝑎𝑟
+
1 − 𝑟𝑝𝑒𝑟
1 + 𝑟𝑝𝑒𝑟
)
𝛼
𝛼 𝑛
=1 − 1.5879 × 10−3
𝜗1 + 2.7314 × 10−4
𝜗1
2
− 2.3026 ×
10−5
𝜗1
3
+ 9.0244 × 10−7
𝜗1
4
− 1.8000 ×10−8
𝜗1
5
+ 1.7734 ×
10−10
𝜗1
6
− 6.9937 × 10−13
𝜗1
7
(10)

13. 5
The glass covers were purchased next, as they were readily
available at precut dimensions from Lowes. To cover the boxes
completely, the experimenters purchased 18x12 glass. The plas-
tic sheeting was available for free from one of the experimenters,
and the inlet and outlet tubes were irrigation line hose that was
also available for free. Now that all of the materials were gath-
ered, the experimenters were ready to begin assembling the three
boxes.
ASSEMBLY
The first stage of the actual construction was cutting the
three Styrofoam boxes at 15, 25 and 35 degrees, from the top.
The angles were measured using a large woodworking triangle
and the boxes were cut using a utility knife. Next, the black plas-
tic sheeting was installed to the walls inside each box using hot
glue. Once the hot glue was dry, L-shaped rails were installed
near the front edge of all three boxes using hot glue once again.
They were positioned so that the water droplets would fall onto
the rail and move out the outlet pipe. In order to make the boxes
as air tight as possible, the experimenters closed the inlet pipes
temporarily using electrical tape. The electrical tape could be
easily removed to add water or take internal water temperature
measurements. The final and most challenging step of the assem-
bly was adhering the glass covers to the boxes. After resting the
glass covers on the boxes, some of the black plastic sheeting was
hanging over the outside of each box. This was removed using
a utility knife before adding any more adhesive. Using two hot
glue guns, the experiments started adding hot glue to the crevice
between the Styrofoam box and glass cover, filling any spaces by
flowing hot glue into voids. The same process was done for each
of the three boxes. At this point, the experimenters were ready to
test each still.
EXPERIMENT
First, the experimenters temporarily removed the tape seal-
ing the inlet hole and added 1 liter of water to each box and
recorded the initial water temperature. Next, the electrical tape
was added to seal the inlet holes once again. Then, the boxes
were set out in the sun at 11AM on November 22nd, 2015. The
experimenters measured the internal water temperature of each
box, as well as the distilled water volume collected out of each
still at each hour.
The figure shows all the three solar stills kept A thermocou-
ple was used to gather water temperature data. A pyranometer
was used to measure the incident solar energy on every half an
hour starting from the time of measurement.
FIGURE 4. Experimental testing
FIGURE 5. Working
MATERIALS USED
Table1 given provides the bill of material for all three solar
stills. The total cost comes out to be $42.91.
For three solar stills, this amounts to be quite cost effec-
tive, roughly around 15$ a box. Models like these would prove
viable in developing countries where there is a lack of potable
water. Moreover, most of the developing countries are located in
warmer latitudes. A simple and economic model like this can be
built using the minimum resources and can be used for heating
and distillation purposes.

14. 6
TABLE 1. BILL OF MATERIAL.
Equipment Cost
Styrofoam Boxes $23.58
Glass Covers $12.87
Sealant $06.46
RESULTS AND DISCUSSION
Theoretical Results
Our theoretical model was based on various assumptions
like there was no heat lost to the surroundings and the material
used behaved like an ideal material. A lot of factors as discussed
earlier were kept constant or assumed to have zero effect on our
project such as there is no water leaking from the still, no temper-
ature gradient in the water, ground reflected radiation was taken
to as zero and diffuse radiation was neglected as its effect was
smaller when compared to the beam radiation. So, here we have
taken the total incident radiation value obtained from the pyra-
nometer readings as the beam radiation component for simplifi-
cation. The readings obtained after solving the equations on EES
software and MS-Excel, we see that there is a linear increase in
the temperature of water as all the heat energy absorbed is used
to raise the temperature without any losses.
FIGURE 6. Temperature readings for cover angle of 15
Figure 6 shows the readings of different temperature values
for cover angle of β = 15 and how the values change with respect
to time. Here, we can see that the ambient temperature hardly
fluctuates and is almost a straight line. The ambient temperature
reading was taken as the average temperature for the correspond-
ing hour in the x-axis. Also, we see that the temperature readings
of calculated temperature of water Twat er and the initial temper-
ature Ti shows a linear growth with time. This is mainly due to
our assumption that there was no loss in absorbed radiation and
all of that was used to raise the temperature of water. The actual
temperature readings were recorded on the day the experiment
FIGURE 7. Time vs Temperature plot for cover angle of 15 degrees
was performed show a parabolic trend. This is because a number
of factors affect the actual temperature of water and there is loss
in energy due to the losses.
FIGURE 8. Temperature readings for cover angle of 25
FIGURE 9. Time vs Temperature plot for cover angle of 25 degrees
Figure 8 and 9 are the theoretical results for cover angle β =
25. A peak value of 102 degrees is reached by the theoretical
temperature value of the water. So, here we expect the water to
begin distillation and and water collection at the other end.

15. 7
FIGURE 10. Temperature readings for cover angle of 35
FIGURE 11. Time vs Temperature plot for cover angle of 35 degrees
Figure 10 and 11 show the readings of different temperature
values for β = 35.
FIGURE 12. Experimental Values of Twater
The actual temperature readings recorded on the day the ex-
periment was performed show a parabolic trend and correlates
with the theoretical results and confirms our assumption that for
the greatest cover angle value we get the maximum distillation of
water. Although , there is a dip in later hours of experimentation,
that is due to drop in outside temperature and thus less available
solar energy to heat the water in the still.
FIGURE 13. Experimental Values for Time vs Twater
CONCLUSIONS AND RECOMMENDATIONS
It can be concluded that the device, build as it was is not
adequate for water purification for drinking purposes. Various
changes and studies can be made to improve the device and in-
crease output water rate. With the assumptions that were made
about the prototype, including no heat or mass loss, the theo-
retical model does result in high enough temperatures and some
water distilled. This means that with improvements to the pro-
totype, the initial goals of purifying water at low cost can be
achieved.
The theoretical results show a linear increase in tempera-
ture. This is because of the original assumption that there is no
heat lost to the surroundings. During testing this was not held
true since the temperature of the water began to drop after 2 pm.
The ambient temperature was low, considering that testing was
performed in the end of November, and the wind contributed to
significant convective losses that were not accounted for within
the model.
It was also assumed that the water evaporated would all
be collected, and there would be no evaporative losses. This
was not the case since the prototype was not airtight, and had 2
small holes for water collection and temperature readings. This
allowed some water vapor to escape and never collect in the
distilled water dish. Inefficiencies in collection was also seen
through the seal of the device. Leakage occurred through the
connection of the glass and Styrofoam not allowing the water to
slide down him collecting tube.
Some constraints of the project included budget, time and
weather. The Project was made with the intent of prototyping
a cost effective means of solar distillation through appropriate
technology that could be found anywhere in the world. There
was also no budget given for the scope of the work this restrained
the purchase of high insulators and other materials that could
have increased the effectiveness and efficiency of the device. The
time allotted for the scope of the work was sufficient for a once-
through design build and test of the prototype. The limited time

16. 8
did not allow for proper inspection of the design requirements
and material properties. It also limited the days available for
testing the output and analyzing the results. The ambient tem-
perature and available solar radiation was low during test day.
The testing was done in November, where conditions are not pre-
ferred for a solar distillation device.
For future work, there are various areas of improvement, re-
considerations and tests that can be done to both improve the
technology and compare the outcomes. It is recommended to
test the devices in the summer where it can be more reasonabil-
ity assumed that there is no heat loss to the environment and the
rate of the water output will be larger due to higher solar radi-
ation. It is also recommended that a larger prototype is built to
increase the rate of water collected and decrease shadow effects
on the system.
Although Styrofoam is cheap and readily available, it cre-
ated various problems. The original idea of painting the mate-
rial with a highly absorptance- black paint, did not last because
the Styrofoam reacted with the paint and corroded. Because the
material was thin, there was significant heat lost that was not
accounted for within the assumptions. For future work, a more
isolative material should be used, or the stills should be placed
in an area of no wind to minimize convection losses. The black
plastic bag should also be replaced by a higher absorptance ma-
terial. The folds and texture in the bag increased the reflective
losses. Also, because the main purpose of the still is to recover
drinking water, the materials must be toxin-free. A different
sealant should be used between the glass and Styrofoam to elim-
inate leakage.
Lastly, the device should be build air-tight with a measur-
ing device included into the build to reduce the need of an extra
whole that allows vapor to leave the device and not be recovered
in the collecting dish.
For future studies regarding improvement in solar still effi-
ciency, the water volume can be varied and compared to optimize
rate of water input for higher rate of output. Other parameters to
be optimized include absorbing surface angle, quantity of cov-
ers, and surface area of the collector. If more time is allotted, a
techno economic analysis of the system could be used to opti-
mize product output while minimizing cost of production before
the system is built.
REFERENCES
[1] Gordes, J., McCracken, H., Understanding Solar Stills, Vol-
unteers in Technical Assistance,. Arlington
[2] Garg, H. P., Mann, H. S., 1976, , Effect of climatic, opera-
tional and design parameters on the year round performance
of single-sloped and double-sloped solar still under Indian
arid zone conditions, Solar Energy, 18(2), pp. 159-163
[3] Arunkumar, T., Vinothkumar, K., Ahsan, A.,
Jayaprakash, R., Kumar, S., 2012, Experimental study on
various solar still designs, ISRN Renewable Energy
[4] Solar Engineering of Thermal Processes, 4 th Edition by
John A. Duffie, William A. Beckman, ISBN 978-0-470-
87366-3, Wiley (2013)

17. 9
EXECUTIVE SUMMARY
This portfolio, submitted as partial fulfillment of the requirements for the MS degree in mechanical
engineering, exemplifies the work that I carried out in my graduate coursework. Specifically, it includes:
1. EFFECTIVENESS OF FIN ON A CPU
This was a group project carried out in MAE 589: Heat Transfer in the spring 2015 semester. Heat transfer
was a course which dealt with understanding how the thermal energy exchange between physical systems. There are
three fundamental ways to transfer the heat conduction, convection and radiation. This topic was chosen because of
greater power generation in the chip, resulting in higher core CPU temperature. Therefore, the ability to dissipate
heat away from CPU become much more important.
As a member of the group, my contribution was to bring about an understanding of the theoretical
knowledge so as to solve the Navier-Strokes and energy equations. My teammate went about understanding how to
build the model in Solidworks and once that was done, we went about setting up the problem and solving it in
numerically by applying commercial flow slover ANSYS Fluent in order to determine all the variations we want to
study.
By doing the ANSYS simulation, the heat sink is much more efficient in dissipating heat when it is rotating
as comparing to when it is stationary. The effect of varying number of fins is marginal, if present at all. Also, further
simulations with increased fin heights are suggested. However, it should be noted that in reality, fin heights are
constrained by limited space within a computer housing.
I included this topic as my first project in portfolio because I was able to study a real-life problem by
applying concepts learn in class. Moreover, this was an area which did not have much research carried upon yet. So
it could not only be a interesting but also worthwhile topic to conduct.
2. OPTIMIZATION OF A SOLAR STILL
This was a group project carried out in MAE 585: Solar Thermal Engineering in the Fall 2015 semester.
According to the previous experience in heat transfer, I decide to study a little bit more on the area relate to thermal.
The topic of optimization of a solar still was chosen because we want to figure out a low cost way to provide
portable clean water by using solar energy.
As a member of the group, my contribution was to apply my knowledge and stuffs learn from this course to
derive the theoretical calculation and result by using EES. My group mates went about building experimental model
and testing it so as to compare the result with theoretical model.
Since my specialization is in the aspect of thermodynamic, I chose this topic to be included in my portfolio.
Then, I had a chance to apply my learnings from other courses to discuss an industrial problem. In addition, the
renewable energy such as Solar and Wind Energy is casting by all over the world. Therefore, by improving the
design, a lot of efficiency problem can be promoted.