Computational and Experimental Investigation of
Cylindrical Heat Sink for Cooling of Electronics
S Sudeepa, Sohan K Gangannavara, Suraj Sa, Sankeerth S Ka, Dr. Jyothi Prakash K Ha
a Department of Mechanical Engineering, PES University, Bengaluru, Karnataka, India
ABSTRACT
Rising incidents of failure of electronic devices due to overheat has been a major concern all
over the world. As the technologies have become so advance the electronic devices are failing
due to overheat. The purpose of this research is to model a heat sink which plays a major role
in improving the performance of the electronic devices. Using Ansys Workbench the designed
heat sink is simulated under natural convection condition in an enclosure. The design model
was manufactured and the natural convection experiment was performed. The findings of the
simulation and the experiment were compared, and they matched with a very low error
percentage. Additionally, the study demonstrates that the average temperature of sink with
perforations has reduced for 10.9% for 4 watt and thermal resistance is reduced by 17%. Further
it was noticed during experimentation that the heat sink with 3mm perforations reaches the
steady state faster.
1. Introduction
Innovative cooling technologies are necessary to meet the ever-increasing heat dissipation
requirements of electronic gadgets. Even while forced convection using fans is still common,
worries about complexity, noise, and dependability open the door to investigating effective
passive cooling solutions. Circular heat sinks are particularly appealing in this domain because
of their built-in symmetry and ability to maximize surface area. Their behavior in naturally
occurring convection, offers both opportunities and problems. Li et al. [1] investigates the
transfer of heat from radial heat sink compromising perforated circles in different orientations.
The results conclude that the radial heat sink with perforation has the best thermal performance.
Higher the number of perforation better is the performance. With addition to this author
concludes that size of the perforation also has an impact on the thermal performance.
Kumar et al. [11] investigates the effect of dimples and protrusions in a standard plate fin heat
sink in a forced convection system. The main reason to refer this author’s work is that, the
author concludes that presence of dimples and protrusions improves the thermal performance
of a heat sink. Song et al. [8] studied the effectiveness of a heat sink with perforated fins on a
cylindrical base. The study was performed to discover the heat sink ability to dissipate heat
with perforated fins. The author concludes that the heat dissipation efficiency is enhanced by
increasing the number of small sized perforation. With addition to that he concludes that
thermal resistance reduces as the number of fins increased because the heat dissipation surface
area is increased. Similarly Li and Byon [10] studied how the orientation influences the heating
efficiency of radial heat sinks with circular rings that were subjected to natural convection.
Author concludes that orientation of heatsink plays a major role in the thermal performance.
The radial heat sink orientation upright has shown the best performance. Maha A et al. [2]
investigated a heat observer with comprises of six symmetrical fins. Three different variants
were examined. The fin with perforations has the highest effectiveness and better thermal
performance. Wong et al. [6] concluded in their research that the inclusion of a fillet improves
the heat transfer performance over the usual design. As the fillet radius increases the heat
transfer performance improves. Yu et al. [12] explains the importance of size and orientation
fins in a heat sink. Three different types of fins with varied size were examined. The transfer
performance was decreased when shorter fins were employed whereas the long and middle fins
has the best heat transfer rate. Elmi et al. [13] also explains the importance of orientations of
fins. The authors examined various orientation of fins and concluded that the semi-triangular
heat sink performs best with reducing the peak temperature vastly when compared with other
orientations.
In summation, these papers goes into the expanding research domain of circular heat sinks
functioning under natural convection. They explain the underlying physical principles that
determine their thermal performance, examine the impact of important design factors, and
investigate cutting-edge optimization methodologies. This extensive analysis paves the way for
a paradigm change in thermal management, marked by increased efficiency and decreased
environmental effect.
2. Numerical Model
2.1. Geometry
The heat sink consists of a circular base, rectangular fins, and a concentric ring to which the
radial fins are attached. The fins are arranged circumferentially at constant intervals, and
perforations in the ring are positioned in the exposed area of the concentric ring at constant
intervals. The number and diameter of the perforation varies from 0 (imperforated) to 6 and 0
to 3mm respectively. Since the perforations are uniformly distributed over the vertical fin
height, the distance between the adjacent perforation decreases as the perforation diameter
increases. The overall radius of the heatsink which will be in contact to the heat source denoted
as R (= 30 mm) and the height of the heatsink H (Hf + Hb, 38 mm). These specific dimensions
are chosen based on the commercially available heat sink. The height of the fin (= H f) is 35
mm, height of the base over which the fins are placed (= Hb) is 3 mm, thickness of the fin (=
tf) is 1 mm. The length of the fin is set to be 14 mm and the outer radius of the fin is 16 mm,
and the fin number is fixed at 23. The selection of material used to manufacture the 6061 T6
aluminum, the number 6061 number indicates the main alloying elements that is magnesium
and silicon, T stands for Temper or Degree of Hardness, “T6” refers temper involves heating
the material to a specific temperature and then quenching it, followed by artificial aging, this
heat treatment process enhances the mechanical properties of aluminum. Aluminum 6 series
has an excellent thermal conductivity of 167 W/m K, it also has good resistance to corrosion,
ease of machining, and the surface emissivity 𝜀 is 0.8.
2.2 Governing Equation
The governing equation describes how the values of the unknown variable (i.e. the dependent
variable) change when one or more known (i.e. independent) variables change. So the
momentum, continuity and thermal energy equations for a laminar 3-D flow are as follows:
 Continuity Equation:
𝜕𝑢 𝜕𝑣 𝜕𝑤
+
+
=0
𝜕𝑥 𝜕𝑦 𝜕𝑧
 Momentum Equations:
𝜌 𝑢
𝑢
𝜕
𝜕𝑢
𝜕𝑢
𝜕𝑢
+𝑣
+𝑤
= −
+ 𝜇∇ u
𝜕𝑥
𝜕𝑦
𝜕𝑧
𝜕𝑥
𝜕𝑢
𝜕𝑢
𝜕𝑢
+𝑣
+𝑤
= 𝑣∇ 𝑣 + 𝑔𝛽(𝑇 − 𝑇 )
𝜕𝑥
𝜕𝑦
𝜕𝑧
𝜌 𝑢
𝜕
𝜕𝑤
𝜕𝑤
𝜕𝑤
+𝑣
+𝑤
= −
+ 𝜇∇ w
𝜕𝑥
𝜕𝑦
𝜕𝑧
𝜕𝑥
 Energy Equation:
𝜌𝐶
𝑢
𝜕𝑇
𝜕𝑇
𝜕𝑇
𝜕 𝑇
𝜕 𝑇
𝜕 𝑇
+𝑣
+𝑤
=𝑘 𝑢
+𝑣
+𝑤
𝜕𝑥
𝜕𝑦
𝜕𝑧
𝜕𝑥
𝜕𝑦
𝜕𝑧
where, 𝜌 is the fluid density, x, y, z- the directions, u, v, w – the velocities, 𝐶 - the heat capacity,
𝛽 – thermal expansion coefficient, T – surface temperature, 𝑇 - the ambient temperature, and
k – thermal conductivity.
The convective heat transfer and the thermal resistance can be calculated using the following
equations.
 Convective heat transfer coefficient:
ℎ=
𝑄
𝐴(𝑇 − 𝑇 )
 Convective thermal resistance:
𝑅=
1
𝐴ℎ
Where A is the total surface area of the fins and h the local convective heat transfer
coefficient.
 The power input of the heater is calculated using the following equation:
𝑃 =𝑉× 𝐼
Where, 𝑃 is the power input to the heater, I is the current supplied and V is the voltage.
3. Simulation and Boundary Conditions
The numerical study for natural convection was conducted by ANSYS Fluent which is
based on the Finite Volume Method (FVM).
When the density of the fluid is temperature dependent, adding heat to the fluid will change its
density. Temperature difference between fluid and surroundings will induce flow by buoyancy
force which inturn is the result of gravity acting on the density differences. Flow caused by
buoyancy with no external devices involved is called Natural Convection. To setup Natural
Convection in Ansys fluent, density was made the function of temperature and turn ON gravity
of - 9.81𝑚/𝑠 . Operating density was set to 1.225 𝑘𝑔/𝑚 and Boussinesq density models is
used which lead to faster convergence. Thermal expansion coefficient [k-1], material property
was set as 0.0033.
The bottom surface of the computational domain was set as a wall where no
mass or heat transfer occurs to imitate actual installation environment, while other surfaces
were openings in order to take into account the natural convection through the domain
boundary. The pressure of the computation domain are set to be the atmospheric pressure (=1
atm) and the ambient temperature is set to be 20 0C. Boundary conditions are shown in Table
123.
Boundary Conditions
Values
Heat Flow
1W to 4 W at intervals of 1 W
Ambient Temperature
20oC
Density (Boussinesq)
1.225 kg/m3
Thermal Expansion Coefficient (1/k) 0.0033
Thermal Conductivity (Aluminium)
167 W/m-k
4. Experimental Work
4.1 The test-rig specifications
The radial heat sink has a 60 mm diameter and total height of the heat sink is 38 mm (H f =
35mm, Hb= 3mm). The heat sink is manufactured using a vertical machining center (VMC).
Then a Electric Discharge Machine (EDM) is used to remove the fillet part between the fins.
(EDM gives the sharp edge between the fins) The heat sink is made of aluminum 6061 T6. A
specific heating pad of 60mm mm diameter was separately manufactured and a voltage
regulator with higher precision was procured. The perforations were made using a 5degree
CNC machine.
Test rig specifications

Heater


Circular heat pad
Maximum heat voltage: 50V

Heatsink




Base diameter: 60mm
Height of base: 3mm
Number of Perforations: 138
Size of the Perforations: 1.5mm –
3mm (interval of 0.5 mm)

Fins


Height of fin: 35mm
Number of Fins: 23

Thermocouples


Number of thermocouples used: 7
Number of thermocouples on the
base: 3
Number of thermocouples on the fins:
7

4.2. The Experimental Procedure
The heating pad was fastened to the base of the heat sink with three thermocouples between
them and four attached to the fins. The thermocouple readings is displayed in a display as
shown in. The heat is varied from 1W to 4W by varying the voltage regulator. The formula P =
V x I is used while setting the heat source.
1. The heat sink without any perforations is fastened to the heat source with the
thermocouples. The heat source is set to 1W and the thermocouple temperature is noted
after it has come to a steady state.
2. The same is done for 2W, 3W and 4W. The temperature for each watt is noted and
averaged.
3. This process is done for different perforations that is 1.5mm- 3mm in an interval of
0.5mm.
The thermocouples data collected from the above steps are used to calculate the temperature
distribution, Nusselt’s number, heat transfer coefficient, heat dissipation from fins and fin
effectiveness.
4.3 Data Reduction
To determine the thermal performance of the heat sink with and without fins the following
assumptions were taken under consideration:
1. There is no change in thermal conductivity with temperature.
2. There is no other heat generation other then the heat supplied at the base.
3. Heat transfer by radiation is neglected.
At steady state conditions, all the heat gained from the base of the heat sink to the tip of the fin
is by convective mechanism released to the surrounding environment. From Newton law of
cooling and Fourier law we get [put ref.]
𝑞
𝑞
= 𝑘𝐴
𝑑𝑇
𝑑𝑥
= ℎ𝐴 (𝑇 − 𝑇 )
A heat flux of (356 W/m2, 712.22 W/m2, 1068.33 W/m2, 1424.44 W/m2) is achieved when
the heater pad applies a heat of 1 to 4 W to the heat sink's base. The following formulae were
used to compute the heat transfer coefficient for the cylindrical vertical heat sink:
.
Nu
H
= 0.525 GrPr ×
L
𝑅𝑎 =
g × β × (T − T ) × d × 𝑃𝑟
v
h=
Nu × k
d
where,
β=
1
T +T
and T =
T
2
To calculate how much heat is lost from a one-dimensional vertical solid fin (conduction +
convection) exposed to ambient temperature T∞, the below equation is used:
h
mk
hPk A × ∆T ×
h
cosh(mL) +
mk
sinh(mL) +
Q
=
cosh(mL)
sinh(mL)
where,
hP
≈
k A
m=
2h
k t
The fin effectiveness can be calculated by dividing the heat dissipated from the heat sink with
fins to that of without fins:
Effectiveness =
Q
Q
To find out heat dissipated without fin the below equations are used:
T =
𝐺𝑟 =
Nu
T +T
2
g × β × (T − T ) × x
v
⎡
0.386 × (GrPr) .
⎢
= ⎢0.825 +
0.492 .
⎢
1+
Pr
⎣
.
The above correlation for the Nusselt’s number is for all values of GrPr.
h=
Nu × k
x
⎤
⎥
⎥
⎥
⎦
The below equation is used to find the amount of heat dissipated from a heat sink without fins:
Q
= h × A × ∆T
where, 𝐴s is the surface area.
5.Results and Discussions
5.1 Effectiveness of Radial Heat Sink with Perforation
The Effectiveness of a heat sink presents a distinct picture about the performance of various
designs which may be assessed by the ratio of the heat dissipated with the fins to that of the
sink without fins. The efficacy of the heat sink for various diameters range from 0 - 3 mm for
diverse heat loss is illustrated in Figure 123
5.2 Comparison of CFD and Experimental Results
Temperature values were measured from a thermocouple placed on the heat sink, the average
of the readings was tabulated. CFD results are compared with the experimental results and an
error percentage ranging between 0.35-5.47 % for average temperature and an error
percentage ranging between 1.26-14.63 % for thermal resistance is observed. The comparison
results with the error percentage for average temperature is shown in Table 4.1- 4.5 and for
thermal resistance is shown in Table 4.6-4.10.
5.2.1 Comparison of CFD and Experimental results of average temperature for various
diameters.
The experimental average temperature to simula on average temperature obtained are can
be seen in the above graphs. It is clear from the graphs that both experimental and CFD results
are in agreement.
5.2.2 Comparison of CFD and Experimental results of Thermal Resistance for various
diameters
The experimental Thermal Resistance to simula on Thermal Resistance obtained are
compared in above graphs. It is clear from the graphs that both experimental and CFD results
are in agreement.
6. Proposed Design
Radial heat sink with an edge cut with the same dimension is used. The Fin thickness of 1 mm
and five edge cuts of 7 x 4 mm in dimensions are made to enhance the perimeter and area, this
also gives a better heat transfer rate. This is designed in SOLIDWORKS and simulated on
ANSYS, temperature contour are shown in Figure 4.14.
6.1 Comparison between the combination of edge-cut fins with perforations and the radial heat
sink with perforations
The 3mm perforated radial heat sink shown in Figure 3.2.(B) and the radial heat sink with
combination of perforations and edge cut fins shown in figure 3.9 is simulated in ANSYS using
the boundary condition mentioned in Table 3.1. The results were compared and shown below.
The thermal resistance obtained from calculation for radial heat sink and radial heat sink
with edge cut is shown in comparison plot Figure 4.16.
The effectiveness was obtained with calculation for radial heat sink and radial heat sink with
edge cut is shown in the comparison plot Figure 4.17.
7 Conclusion and Scope for Future Work
As a part of this study, a radial heat sink with perforation is numerically developed and verified
using literature. The revolutionary design, radial heat sink with a blend of perforation and edge
cut fins to attain superior heat transfer performance with greater efficacy and reduced thermal
resistance.The simulations are performed in steady-state calculation using the Boussinesq
model. A radial heat sink with perforations is fabricated and experimental analysis is conducted.
The experimental results are validated with CFD analysis. The radial heat sink with edge cut
and perforation is contrasted with the heat sink with straightforward fins with the same
dimension to emphasise the merit of the new design. The simulated results are presented and
the relation between geometric parameters and output parameters is investigated.
7.1 Salient Conclusions




It is observed by comparing an imperforate heat sink to that of perforated heat sink for
various heat loads and the average temperature was observed to be reduced by 9.5 %
for 1 W power input and 10.9 % for 4 W of power input.
It is compared to an imperforate ring, the optimised perforated ring of the radial heat
sink demonstrated a 17% lower thermal resistance, with a 37% reduction in ring mass.
It is observed during experiment, the heat sink with 3mm perforated ring reached the
steady-state faster than that of imperforated ring.
It is observed that effectiveness is a function of perimeter by area. It plays a major role
in selection of heat sink i.e with increase in perforation diameter the effectiveness is
increased by 7.65. When an edge cut fin is incorporated to this set up the effectiveness
increases by 82.31%.
7.2 Scope for Future Work




Optimization of current proposed design with different edge cut fin width and thickness.
Investigation of the radial heat sink with coupled edge cut and perforations through
experimentation.
Exploring the heat transfer behaviour in forced convection set-up.
Investigation of application-specific heat sinks.
8 References
[1] Bin Li, Sora Jeon, Chan Byon.,(2016).Investigation of natural convection heat transfer
around a radial heat sink with a perforated ring. ELSEVIER International Journal of Heat and
Mass Transfer, volume 97, 705-711.
[2]Maha A. Hussein , Vinous M. Hameed b, Hussein T. Dhaiban (2022).An implementation
study on a heat sink with different fin configurations under natural convective
conditions.ELSEVIER,Case Studies in Thermal Engineering 30 - 101774
[3] Seyfi Şevik, Özgür Özdilli, Experimental and numerical analysis of the splay impact on
the performance of splayed cross-cut fin heat sink,ELSEVIER, International Journal of
Thermal Sciences, Volume 170, 2021, 107101, ISSN 1290-072.
[4] Deepak Gupta, Vignesh Venkataraman , Rakesh Nimje., (2014). CFD & Thermal Analysis of
Heat Sink and its Application in CPU:Semanticsscholar, International Journal of Emerging
Technology and Advanced Engineering , volume 4 , 2250-2459.
[5] T Saravanakumar, D Senthil Kumar .,(2019). Performance analysis on heat
transfer characteristics of heat SINK with baffles attachment.ELSEVIER , International
Journal of Thermal Sciences 142 14-19.
[5] Kok-Cheong Wong , Sanjiv Indran ,(2013).Impingement heat transfer of a plate fin heat
sink with fillet profile.ELSEVIER, International Journal of Heat and Mass Transfer , 65 1-9
[7] S. M. Pouryoussefi and Y. Zhang, (2014). Experimental Study of Air-Cooled
Parallel Plate Fin Heat Sinks with and without Circular Pin Fins between the Plate Fins, JAFM
Journal of Applied Fluid Mechanics, vol 8, No 3 pp 515 - 520.
[8] Gihyun Song, Dong-Hwa Kim, Dong-Hyung Song, Ju-Bin Sung, Se-Jin Yook, (2021).
Heat-dissipation
performance
of
cylindrical
heat
sink
with
perforated
fins,ELSEVIER, International Journal of Thermal Sciences, Volume 170 , 107132.
[9] Dong Ho Shin, Dong Kee Sohn, Han Seo Ko., (2018). Analysis of thermal flow around
heat sink with ionic wind for high power LED. ELSEVIER ,Applied Thermal Engineering,143
376-384
[10] Bin Li, Chan Byon.,(2015). Orientation Effects on Thermal Performance of Radial Heat
Sinks with a Concentric ring Subjected to Natural Convection .ELSEVIER
International Journal of Heat and Mass Transfer,volume 90, 102-108.
[11] Sharath Kumar S N, Sathish S , Purushothama H R., (2021). Heat Transfer Analysis
of Plate Fin Heat Sink with Dimples and Protrusions:IIETA: Investigation of New
Designs.International Journal of Heat and Technology, 39, pp. 1861-1870.
[12] Seung Hwan Yu, Kwan Soo Lee, Se jin Yook., (2011). Optimum Design of a
Radial Heat Sink under a Natural Convection.ELSEVIER , International Journal of Heat and
Mass Transfer, volume 54, 2499-2505.
[13] M. Ahmadian-Elmi , M. Mohammadifar, E. Rasouli, M.R. Hajmohammadi.,(2021).
Optimal design and placement of heat sink elements attached on a cylindrical heat-generating
body for maximum cooling performance.ELSEVIER, Thermochimica Acta, volume 700,
178941.
[14] Robert Tucker , Mehdi Khatamifar, Wenxian Lin , Kyle McDonald., (2021).
Experimental investigation of orientation and geometry effect on additive
manufactured
aluminium LED heat sinks under natural convection.ELSEVIER, Thermal
Science and Engineering Progress , Volume 23, 100918
[15] HoSung Lee.2011. Thermal Design Heat Sinks, Thermoelectrics, Heat Pipes, Compact
Heat Exchangers, and Solar Cells