Of the Active Cooling Techniques, Jet impingement achieves high localized heat transfer rates. Introduction of swirl is one of the methods of augmentation of heat transfer rates. The current work aims at verifying the expression derived in our previous work experimentally. Three cases, for which simulations were performed previously, are executed. The required ducts are manufactured by additive manufacturing. Thermistors are used for measuring temperatures. Anemometer is used to monitor air flow rates. Smoke tests are executed to demonstrate the generation of swirl and then experimentation is executed to study the heat transfer characteristics. The experimental results are in agreement with those of simulation results

1. http://www.iaeme.com/IJMET/index.asp 493 editor@iaeme.com
International Journal of Mechanical Engineering and Technology (IJMET)
Volume 9, Issue 11, November 2018, pp. 493–499, Article ID: IJMET_09_11_048
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=11
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
HEAT TRANSFER DURING MULTI SWIRL JET
IMPINGEMENT: EXPERIMENTATION
N. V. S. Shankar
Research Scholar, Department of Mechanical Engineering,
GITAM University, Visakhapatnam, India
Dr. H. Ravi Shankar
Professor, Department of Mechanical Engineering,
GITAM University, Visakhapatnam, India
ABSTRACT
Of the Active Cooling Techniques, Jet impingement achieves high localized heat
transfer rates. Introduction of swirl is one of the methods of augmentation of heat
transfer rates. The current work aims at verifying the expression derived in our
previous work experimentally. Three cases, for which simulations were performed
previously, are executed. The required ducts are manufactured by additive
manufacturing. Thermistors are used for measuring temperatures. Anemometer is
used to monitor air flow rates. Smoke tests are executed to demonstrate the generation
of swirl and then experimentation is executed to study the heat transfer
characteristics. The experimental results are in agreement with those of simulation
results.
Key words: Jet Impingement, Swirl, Heat Transfer, Smoke Test, Thermistors.
Cite this Article: N. V. S. Shankar and Dr. H. Ravi Shankar, Heat Transfer During
Multi Swirl Jet Impingement: Experimentation, International Journal of Mechanical
Engineering and Technology 9(11), 2018, pp. 493–499.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=11
1. INTRODUCTION
Increasing processing power of chips is leading to higher heat generation in processors [1].
High temperatures are the primary cause of failure of 67% electronics [2]. Cooling of
electronics is thus an important aspect relating to functioning of the equipment. There are two
types of cooling: Active cooling and Passive cooling. Passive cooling is the process of
cooling without the use of extra energy while active cooling involves use of explicit fluid
circulation systems over heat sinks. Jet impingement is an active cooling process in which jet
is impinged on the surface to be cooled. Zuckerman and Loir [3], Sagar Chirade [4], Anupam
Dewan, et al [5] reviewed the jet impingement process and summarized the correlations of
heat transfer during jet impingement. Air jet impingement applications in food processing
were presented by A. Sarkar, et al [6]. Simulations and Experimentation were executed by

2. Heat Transfer During Multi Swirl Jet Impingement: Experimentation
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many researchers to understand the phenomenon of heat transfer. Sajad Alimohammadi, et al
[7] used both numerical simulations and experimental procedure to study the heat transfer
during unconfined single jet impingement. The Re values simulated are between 6000 and
14000 with z/D ranging from 1 to 6. Equation (1) has been proposed.
0.518 0.4 0.064
0 0.633Re Pr ( / )Nu z D (1)
Benmouhoub and Mataoui [8] used numerical simulations to investigate the heat transfer
characteristics when slot jet is impinged on a moving flat plate. Hwang and Cheng [9], [10]
used anisotropic t2
-εt heat-transfer model together with the anisotropic k-ε turbulence model
for simulating heat transfer during swirling couette flow. Rattner [11] performed 1000 cfd
simulations to generate the correlations for k factor and Nu during jet impingement in micro
fin heat sinks. Equations (2) & (3) were proposed by them.
20
1
Re
10
c j d j
bj
j j
j j
j
p tha
D D
k

 
    
    
     

 (2)
20
1
Re
0.29
Pr 10
c j d j
bj
j j
j j
j
p tha
D D
Nu

 
    
    
     

 (3)
Nasif, et al [12] used CFD simulations to study the effectiveness of cooling piston with oil
jet impingement. SST model was used and RANS equations were solved during this process.
Farida Iachachene, et al [13] performed numerical simulations to investigate the heat transfer
due to impinging slot jet in a rectangular cavity. Several flow regimes are observed depending
on the jet exit in the slot. Numerical correlations are formulated so as to compute the Nusselt
number. The Correlation that has been derived is given in equation (4).
3 2 0.71546
10 (66,55 3,23 0.068 )Ref fNu L L
   (4)
Jia, et al [14] performed numerical simulations to study the effect of upstream and
downstream shaped ribs on heat transfer during flow when cooling turbine blades. ν2
f-kε
model is used during simulations. Xu, et al [15], using numerical simulations, investigated the
effect of five different types of vortex generator on heat transfer during flow in a rectangular
channel.
Modak, et al [16] investigated experimentally the use of Cu2O-Water nanofluid during
single jet impingement form a flat surface. Different values of Re, z/D and concentrations (Φ)
are experimented during this process. Ichimiya & Yamada [17] experimentally studied the
heat transfer due to circular impinging jet form a confining wall. Shen, et al [18] using CFD
techniques, investigated into heat transfer augmentation during jet impingement by the use of
dimples and protrusions.
Rodriguez, et al [19] compared different methods of modeling helicoloids for generating
swirling flow fields. Impact of Re and S on Heat transfer, central recirculating zone are
discussed. Numerical simulations carried out for this purpose are presented. Bakirci, et al [20]
& Bilen, et al [21] conducted experiments for flow visualization and study heat transfer in
both multi-channel impinging jet (MCIJ), Swirling Impinging Jet (SIJ) and conventional
impinging jet (CIJ). Experimental results indicated significant improvement in radial
uniformity of heat transfer in SIJ compared to the MCIJ and CIJ. Herrada, et al [22] used
axisymmetric cfd simulations to study the effect of a swirl number S and a vortex core length
d on the mechanical characteristics of the flow at moderate Reynolds numbers. Amini Y, et al
[23] practically studied the use of twisted tape inserts in augmenting heat transfer during jet
impingement cooling. During this process, the effect of swirl on the surface pressure is
studied in detail. Swirling was achieved aerodynamically. Prasad, et al [24] used numerical

3. N. V. S. Shankar and Dr. H. Ravi Shankar
http://www.iaeme.com/IJMET/index.asp 495 editor@iaeme.com
simulations to study the heat transfer from sparse and dense pin fin heat sinks during jet
impingement. Zahir U Ahmed, et al [25] used RANS approach with RNG k–ε model is used
for investigating the effects of inflow conditions on the transition from free-to-impinging and
non-swirling-to-swirling (impinging) jets. 2D axi-symmetric analyses are performed during
this process. The analyses and swirl numbers tested have targeted flow conditions whereby no
vortex breakdown is expected to occur. Kinsella, et al [26] indicated that the main reason for
augmentation of heat transfer in swirling jets is due to increase in turbulence. It is also found
during their investigations, that at lower H/D ratios, the heat transfer decreases as higher
stagnation area is generated because of blockage due to swirl generator. It has also been
observed by them that the optimum degree of swirl from a heat transfer perspective is a
function of the nozzle to impingement surface spacing. Ortega-Casanova [27], [28] gave
expressions relating to heat transfer from a heated plate when subjected to swirl jet
impingement. The expressions given are for constant wall boundary conditions.
Sergey, et al [29] employed stereo PIV technique using advanced pre- and post-processing
algorithms for studying the turbulent swirling jets. During their study, they observed early
breakdown of vertex when S=1.0 and 0.71, but a lengthy vertex for S=0.41. The vertex
breakdown at higher S values leads to greater turbulent energy and thus significantly large
values of the third-order moments determining the turbulent diffusion of the energy. Shuja, et
al [30] indicated that swirl increases irreversibility due to heat transfer while reduces fluid
friction. Erik [31] gave expressions for mathematically modelling swirling flow and
evaluating various parameters in the flow. Koichi Ichimiya and Koji Tsukamoto [32]
investigated the heat transfer when swirling laminar jet is being impinged on a flat plate.
Ekkad, et al [33] investigated the heat transfer augmentation by inducing swirl in impinging
cooling jets by introducing them at an angle during cooling turbine blades. Three different
lateral hole configurations with three different Re values are tested.
2. EXPERIMENTAL SETUP
Based on the literature reviewed, it can be seen that there are no numerical correlations for
Multi-Swirl Jet Impingement. In our past work [34], a set of 42 simulations were executed so
as to obtain a relation for predicting heat transfer coefficient during multi-swirl jet
impingement with Re ranging from 11000 to 33000, swirl generators with angles 0°, 90°,
180°, 360° and z/D ranging from 4.00 to 4.50. The correlation for calculating Nusselt number
is given by equation (5). The heat transfer coefficient is further calculated using equation (6).
0.8764 0.33 0.0364 0.04846 0.4454
3.347834 ( )zNu Re Pr Si I
D
 (5)
hD
Nu
K
 (6)
The current work focuses on experimental verification of equation (5). For this purpose,
ducts with swirl generators are 3D printed.
3. FABRICATION OF DUCTS
Three ducts with swirl angles of 90°, 180° and 360°, and a duct with no swirl generator are
manufactured using additive manufacturing. The ducts are modelled in Creo. Tool paths are
generated using Cura. For this PLA material is used. Wanhao Duplicator i3 printer is used to
fabricate the ducts. The ducts are printed at a temperature of 205°C at a speed of 20mm/s.
Grid infill is used and a wall thickness used is 2mm. Figure 1 shows the fabricated ducts.
Each duct contains 9 (3X3) jet exits at pitch of 15mm.

4. Heat Transfer During Multi Swirl Jet Impingement: Experimentation
http://www.iaeme.com/IJMET/index.asp 496 editor@iaeme.com
Figure 1 Fabricated ducts
4. EXPERIMENTAL SETUP
The schematic of the experimental setup at given in [35] is shown in figure 2. The
experimental setup uses six 100K NTC thermistors which used for measuring temperature.
These thermistors are interfaced to computer using Intel Edison using resistance break circuit
shown in figure 8. This fabricated circuitry is shown in figure 3. Of the six thermistors, four
are placed on 60mm X 60mm X 15mm Aluminium plate as in figure 4. One is placed at the
duct exit to measure T∞ as shown in figure 5. Average of the temperature measured by the
thermistors on the Al block gives T. Another thermistor is placed at the exit of complete setup
so as to read exit air temperature Te. The heat transfer coefficient is computed using equation
(7). The mass flow rate is measured using vane anemometer. This shown in figure 6.
Complete experimental setup is shown in figure 7. It may be noted that the heat input is given
using 12706 Thermoelectric Chip.
( ) ( )p e avmC T T hA T T    (7)
Figure 2: Schematic of Experimental Setup
used
Figure 3: Thermistor setup used for measuring
temperatures
Figure 4: Thermistors placed
on Aluminum block
Figure 5: Thermistor
placed at duct exit
Figure 6: Flow exit from blower

5. N. V. S. Shankar and Dr. H. Ravi Shankar
http://www.iaeme.com/IJMET/index.asp 497 editor@iaeme.com
Figure 7: Complete Experimental Setup Figure 8: Resistance break circuit used for
interfacing thermistors
5. RESULTS AND DISCUSSION
Smoke tests are initially performed using the ducts. With the increase in swirl angle, an
increase in cone angle of the jet exiting the nozzles in the duct are observed. The increasing
cone angle indicates the increase in swirl. This is shown in figure 9. It may be noted that the
smoke tests are captured using high speed camera at 960fps. The cone for 360° swirl
generator could not be captured as the spreading of smoke is very high due to large cone
angle. The blower generates an air flow with a velocity of 16m/s. This is directed via duct on
to aluminium plate via nine nozzles with diameter of 10mm each. As indicated heat input is
given using a TEC. Temperatures are noted when steady state is reached. Table 1 summarizes
the experimental data. Tav denotes the average surface temperature. T∞ indicates the air exit
temperature from the nozzle. Te indicates the air exit temperature from the experimental setup.
Heat Transfer Coefficient is computed using expression (7). In all the cases, H/D is
maintained at 4. The error that was obtained during experimentation is around 13% indicating
the validity of the expression derived.
Figure 9: Smoke Test Result. Starting from left (a) No Swirl generator used, (b) with 90° helix swirl
generator, (c) with 180° Helix swirl generator, (d) with360° Helix swirl generator
Table 1: Experimental Data
Name Tav T∞ Te
Exit
Velocity
(m/S)
Exitmass
flowRate
(Kg/S)
Heat
Removed
(W)
Surface
Area
HeatTransfer
Coefficient
Experimental
HeatTransfer
Coefficient
Simulated
Error
NoSwril 363 313 318 8 0.01176 11.8188 0.0036 65.66 75.93 13.52%
Swirl 90° 343.5 313 318 8 0.01176 11.8188 0.0036 107.64 125.52 14.24%
Swirl 180° 344.5 313 319 8.2 0.012054 12.11427 0.0036 106.83 129.16 17.29%

6. Heat Transfer During Multi Swirl Jet Impingement: Experimentation
http://www.iaeme.com/IJMET/index.asp 498 editor@iaeme.com
6. CONCLUSIONS
This work is continuation of our previous work published in [34]. The work aims at verifying
the expression that is derived for computing Nusselt number and thus heat transfer coefficient,
in our past work, for Multi-Swirl Jet impingement cooling. When experimenting 9 (3X3) jets
are used. The ducts are fabricated using additive manufacturing techniques using PLA
material. Thermistors are used for measuring temperature. Anemometer is used for measuring
air velocity. Initially smoke tests are performed to demonstrate the swirl generated.
Experimentation is then performed to compute the heat transfer rates. The heat transfer rates
computed from experimental data are in agreement with that of numerically simulated values.
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