This experimental study examines how forced convective flow affects heat transfer
properties in a rectangular channel with staggered pin fins featuring different perfo-
ration patterns under constant heat flux conditions across Reynolds numbers (Re)
ranging from 2.0 103
to 12 103
. The study compares cylindrical pin fins with solid
pin fins and those featuring circular longitudinal (L), longitudinal/transverse (LT),
and longitudinal/transverse/vertical (LTV) perforations to determine optimal perfo-
ration configurations for enhanced heat transfer performance. The experiment uses a
Peltier module to generate heat on one side, utilizing the Armfield Free and Forced
Convection Heat Transfer Service Units HT 19 and HT10XC. The results showed that
perforated pins significantly raise Nusselt number (Nu) over solid pins: 7% for L, 30%
for LT, and 64% for LTV perforations. Pressure drops are reduced by 10% for L, 17%
for LT, and 25% for LTV perforations relative to solid pins. At lower Reynolds num-
bers, the overall enhancement ratio peaks, notable for reaching a 40% rise with LTV-
perforated pin fins. Additionally, fin effectiveness improves significantly: 14, 34, and
57% higher for L, LT, and LTV perforated pin-fin arrays, respectively. This study
showcases potential applications in electronic cooling systems, promising improved
heat transfer efficiency.
Keywords: pin-fin heat sink, Peltier module, perforation pattern, heat transfer
coefficient, electronic cooling
1. Introduction
The relentless push for higher performance in microelectronics, coupled with the
drive for miniaturization, has made efficient thermal management a paramount concern
in modern electronic design.
As electronic devices become more compact and powerful,
the ability to dissipate heat effectively is crucial to ensuring their performance, reliabil-
ity, and longevity. The relationship between component temperature and the opera-
tional efficacy of electronic devices is well established–lower temperatures generally
equate to better performance and a longer lifespan for these components.Heat sinks play a critical role in managing the thermal loads of electronic devices.
By facilitating heat transfer from heat-generating components, heat sinks help main-
tain temperatures within safe operating limits. The challenge lies in designing heat
sinks that not only efficiently dissipate heat but also fit within the increasingly
constrained spaces of modern electronics.
Perforated fins are especially effective at improving heat transfer because of their
greater ratio of surface area to volume, resulting in lighter heat sinks and more
uniform temperature distribution compared to solid fins. Research consistently shows
that heat sinks with perforated pin-fins outperform those with solid pin-fins in terms
of thermal efficiency [1–5]. Studies on various pin-fin configurations further under-
score these findings [6–10].
Additional studies have further underscored the advantages of specific perforation
geometry. Ibrahim et al. [11] highlighted the benefits of triangular perforations in
reducing pressure drop and increasing the Nusselt number, while Chingulpitak et al.
[12] noted that enlarging both the quantity and size of perforations in pin-fins results
in better thermal performance.
Chin et al. [1] demonstrated that perforations enhance convection heat
transmission by 45% and reduce pressure drop by 18% compared to solid pins.
Moreover, perforations reduce the heat sink’s weight by 37%, improving overall
heat transfer. Kore et al. [13] found that conical perforations in pin-fin heat
sinks significantly enhance flow turbulence and heat transmission. According to
Gupta et al. [14], circular perforations improve thermohydraulic performance by
28%, with a temperature reduction of approximately 16 K when using
square-shaped perforations.
Other studies have investigated the effects of varying perforation sizes and quan-
tities on the efficiency of heat sinks. Choure et al. [15] found that enlarging both the
quantity and diameter of perforations leads to a reduced pressure drop and an
enhancement in the Nusselt number. Foo et al. [16] found that perforated pin-fin
arrays, subjected to varying inlet velocities, transfer more heat and experience a lower
pressure drop compared to solid pin arrays.
Hayder et al. [17] examined the influence of pin geometry on thermal efficiency,
concluding that round pin fins facilitate better heat transfer than those with sharp
edges. Similarly, Kotcioglu et al. [18] discovered that circular pin fins demonstrate a
lower pressure drop in comparison with hexagonal or square pin fins. Hwang et al.
[19] proposed a thermal optimization model demonstrating that varying fin thickness
can reduce thermal resistance, particularly in water-cooled heat sinks. Koga et al. [20]
designed an enhanced heat sink using the Topology Optimization Method tailored for
small-scale applications, with an emphasis on reducing pressure drop while maximiz-
ing thermal dissipation.
In the existing literature on heat sink optimization through perforations, most
studies have focused on individual types of perforations [8, 12, 21–24], resulting in a
fragmented understanding of the effectiveness of circular perforated cylindrical fin
pin heat sinks.
Building on this extensive foundation, the current investigation seeks to push the
boundaries of heat sink design by examining the impact of various perforation con-
figurations on heat transfer efficiency. This research aims to identify the optimal
perforation pattern that maximizes heat dissipation efficiency. Experimental analysis
will be conducted on heat sinks with solid pin-fins, longitudinal perforations, longi-
tudinal/transverse perforations, and longitudinal/transverse/vertical perforations
across different inlet velocities and Reynolds numbers. Key performance metrics,including the Nusselt number, friction factor, thermal resistance, hydrothermal per-
formance, fin efficiency, and effectiveness, are evaluated to determine the most
effective design.
In essence, this study aspires to advance the state of the art in thermal manage-
ment for electronic devices, providing insights that could lead to more efficient and
compact cooling solutions. By systematically exploring and analyzing the effects of
various perforation configurations, this research aims to contribute valuable knowl-
edge to the ongoing quest for optimal heat sink designs.
2. Methods
The experiment was conducted using the Armfield Unit for Heat Transfer by Free
and Forced Convection, designed to demonstrate the principles of natural (free) and
forced convection. As depicted in Figure 1, this unit features a bench-mounted verti-
cal rectangular air duct (300 350 mm and 950 mm in height) positioned above a
centrifugal fan. Inside the duct, a hot wire anemometer measures and displays the air velocity on a dedicated display unit. The duct includes a 150 150 mm test section at
the rear wall, allowing the insertion of various heat-transfer surfaces.
Each heat sink unit is equipped with a polycarbonate sheet with low thermal
conductivity at its base, serving as an insulator to ensure upward heat flow through
the heat sink. A 60-watt Peltier module (heating pad) with stabilized heat flux mimics
the thermal heating of electronic components. The heat sink, characterized by high
thermal conductivity, is connected to the heating pad using high-conductivity thermal
tape to minimize contact resistance. Thermocouples positioned on the heat sink’s base
measure the temperature across the surface.
The duct’s front wall is constructed from acrylic to allow clear observation of the
heated surface and measurement sensors. A throttle that can be adjusted manually regu-
lates the airflow, while pressure sensors placed both upstream and downstream of the
orifice plate monitor the difference in pressure across the test section. Thermocouples
measure air temperatures before and after the heated surface, as well as base and surface
temperatures at various points along the extended surface of the heat exchangers.
The base plate has seven primary thermocouples (T3–T9) to measure its surface
temperature, while the pins have eight secondary thermocouples (T1–T8) to measure
extended surface temperatures. Air inlet and outlet temperatures are recorded by sen-
sors T1 and T2 at the duct’s top and base. Thermocouple attachment points are covered
with adhesive for protection. Air velocity can be adjusted from 0 to 12 m/s, depending
on local mains voltage and supply frequency, with the sensor permanently mounted in
the duct and connected to the console via a plug and socket. All thermocouples are
“Duplex,” with primary thermocouples using miniature plugs and secondary thermo-
couples using two-way edge connectors suitable for the Risepro Data Logger.
Four different configurations of staggered pin arrays have been used, namely:
i. Solid pin-fin heat sink depicted in Figure 2a,
ii. Heat sink with longitudinal perforated pin-fins shown in Figure 2b,
iii. Heat sink featuring both longitudinal and transverse perforated pin-fins
illustrated in Figure 2c, and
iv. Heat sink incorporating longitudinal, transverse, and vertical perforated pin-
fins as shown in Figure 2d.
Each pin-fin array contains 23 pins, 8 mm in diameter and 45 mm in height, with a
pitch of 20 mm.
2.1 Experimental procedure
The experiment entailed testing four types of heat sinks at five flow speeds (0.5,
1.0, 1.5, 2.0, and 2.5 meters/second) with a constant heat flux of 5000 Wm2
, resulting
in 20 experimental runs using a consistent approach.
2.1.1 Preparation
i. The laboratory air conditioning system was activated to stabilize the room
temperature at 25°C.
The HT10XC heat transfer service equipment was powered on.
iii. The centrifugal ventilator was started to induce fluid flow through the test
section. The air velocity at the entrance was adjusted to the desired value and
maintained constant.
2.1.2 Measurements
i. The digital differential manometer was zeroed to record the pressure
difference.
ii. The variable transformer was set to provide the required input power
to the heating pad, monitored via a digital wattmeter to ensure the desired
heat flux.
iii. The system was allowed to reach steady-state conditions over approximately
80 minutes, as determined by stable specimen temperatures (fluctuations
within 0.1°C over 10 minutes).
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