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1. REVIEW PAPER- ON ENHANCEMENT OF HEAT TRANSFER USING RIBS
Adiraja.M 1
, Hariram.P.S 2
, Varun Kumar 3
1 & 2 - III Year Mechanical Students, 3-Assistant Professor
adiraja098@gmail.com,bvk@vcet.ac.in
Department of Mechanical Engineering
Velammal College of Engineering and Technology- Madurai
ABSTRACT:
A Review paper based on
investigations of heat transfer enhancement
using ribs mounted in duct (Rectangular or
Square channel). Repeated ribs have been
used to enhance heat transfer, promote
turbulence and enhance convective heat
transfer. Local heat transfer coefficients were
obtained at various Reynolds number (Re)
with in a turbulence flow regime. The heat
transfer is low due to the low heat transfer
capability between absorber plate and air
heater duct. To improve heat transfer by
creating turbulence flow artificial roughness.
Here many authors conduct investigation of
heat transfer by using various shape of ribs
such as Continuous Ribs, Transverse Ribs,
Angle Ribs, Multi V -Ribs, Arc Shaped Ribs
etc. The article is based on comprehensive
review of work carried out in the technology
KEYWORDS: Heat transfer, Ribs, Artificial
roughness
1. INTRODUCTION:
Heat transfer enhancement is a purely
geometric analysis that is presented in this paper
for a variety of rib geometries. Variation in heat
transfer coefficient on the area of the ribs and the
rib surface itself are available for a wide range of
rib parameters. The large number of studies of
heat transfer and flow characteristics have been
carried to investigate the effect of rib design
parameter namely rib height, angle of attack,
relative roughness pitch, rib arrangement and rib
cross section. The convective heat transfer along
duct wall can be improved significantly by
introducing the recirculationreverse flow to
increase efficiency axial Reynolds number and
decrease cross sectional area of flow. The heat
transfer rate can be improved by introducing a
disturbance in the fluid flow (breaking the viscous
and thermal boundary layers). Therefore, to
achieve desired heat transfer rate in an existing
heat exchanger at an economic pumping power,
several techniques have been proposed recent
years. The techniques are listed below.
1. Active technique: This technique are more
complex from the use and design part of view as
the method requires some external power input to
cause design modification and improvement of
heat transfer. Various active techniques such as
mechanical aids, fluid vibration, surface vibration,
jet impingement.
2. Passive technique: This technique generally
are surface geometrical to the flow channel by
incorporating inserts, ribs (or) adding device. Heat
transfer can be achieved by rough surface,
extended surface and treated surface.
3. Compound technique: It is combination of
both active and passive technique.
LITERATURE REVIEW
1. Square duct with w-type turbulators:
Desai, yada [1] et al. In this paper
numerical analysis was carried out of three
different angles of turbulators were placed in
square duct with internal W-shaped ribs. It was
performed by CFD (Computational Fluid
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2. Dynamics). The parameters of Reynolds number
range from 10,000-60,000, angle of attack α=90⁰,
60⁰&45⁰, Pitch height (ed) =10, relative
roughness height (edh) =0.043, rib
height=0.0035. It was found that high heat transfer
and pressure drop in angle of attack 60⁰.
2. Rectangular duct with inclined discrete rib:
K.R .Agarwal, B.H.Gandhi [2] et al.
experimentally investigated the effect of gap in
inclined rib on heat transfer and the fluid flow
characteristics of heated surface. The parameters
range of Reynolds number were 3,000-
15,000.pitch distance (ed) =10mm, angle of
attack 45°. The rectangular duct with internal size
(2600mmx181mmx31mm), thickness (6mm),
length (800mm). It was found that the relative
roughness of pitch 7.5 gives better performance
than 10 (or) 5.
3. SAH duct with multi V-shape roughness:
Anil Kumar [3] et al. The study presents
the heat transfer and fluid flow characteristics in a
rib-roughened solar air heater duct (SAH)
channel. It was performed by computational fluid
dynamics (CFD) with multi V pattern ribs ,
Individual parameter of effect of gap of width 0.5
to 2.0 and Re range of 2,000-20,000 at relative
roughness height of (edh)=0.043 , pitchRib
height ratio (ed)=10mm, angle of attack α=60⁰.
While comparing multi V-shape rib with other
relative gap width. Multi V Rib gives better
thermal performance of 3.82.
4. Nozzle rib shape in gas turbine:
Chandrasekhar Bhatt [4] et al. A numerical
investigations is carried out to evaluate the heat
transfer characteristics of nozzle ribs in gas
turbine. The investigations were conducted in
rectangular channel of aspect ratio of (AR) =4:1
with rib to hydraulic diameter ratio (edh) =0.1,
and rib pitch to height ratio (pe) =10&5mm, Re
range of 30,000 for different configurations of
nozzle ribs. Fluid flow simulation results of
different configurations of nozzles provides better
heat transfer characteristics over the conventional
45⁰ ribs.
5. Rectangular rib in SAH duct:
Mohammed rayed facraqui [5] et al. A
numerical study on effect of rectangular shaped
ribs in different patterns on thermal performance
of solar air heater duct. The work is concerned
with two dimensional study done to predict the
influence of transverse rectangular cross-sectional
ribs. They experimentally investigated on single
wall arrangement, staggered arrangement and
inline arrangement of ribs. Individual parameters
of Reynolds number range of 3,000-18,000, pitch
height (ed) =10mm, artificial roughness height of
0.018-0.052, angle of attack α=60⁰, and
rectangular duct ratio of 6.8-11.5. It was found
that inline ribs give better thermal performance of
1.82 than staggered counter parts of relative gap
widths.
6. Circular tube having transverse ribs:
Sujaykumar, saha [6] et al. The
experimental factor of Reynolds number and
Nusselt number data for laminar flow of viscous
oil through a circular duct having integral
transverse rib roughness and fitted with twisted
tapes with oblique teeth are presented. The
parameter of range Re 5,000-20,000, tooth angle
30⁰, 45⁰, 60⁰. Rib pitch (pe) =20, 13.33and 10.
Twist ratio y=2.5 &5.0 rib height (ed) =0.0526,
0.07894, 0.10526. The major findings of this
experimental investigations are that the twisted
tape with oblique teeth results in combination with
integral transverse ribs roughness performs
significantly better than individual enhancement
technique acting alone for laminar flow through a
circular duct up to a certain value of fin parameter.
ISBN-13: 978-1539669203
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Proceedings of ICRTE-2016
©IIRDEM 201649

3. It is observed that both friction factor and Nusselt
number decreases.
7. Helical rib:
Pong jet Promvongeet et al [7], report
carried out in a double tube heat exchanger using
the helical-ribbed tube fitted with twin twisted
tapes have been investigated experimentally.
Individual parameter are a Single rib-height to
tube-diameter ratio, e/DH= 0.06 and rib-pitch to
diameter ratio, P/DH= 0.27 as the tested section
double twisted tapes with twist ratio, Y, in the
range of 2.17 to 9.39 is to create vortex flows
inside the tube. They reveal that the co-swirling
inserted tube performs much better than the
ribbed/ smooth tube, co-swirl tube at Y≈8 yields
the highest thermal performance at lower
Reynolds number (RE).
8. skew-rib in rectangular narrow channel:
S.W. Chang et al [8],conducted heat
transfer measurements over a skewed-rib
roughened surface in a rectangular narrow
channel with two equal-area flow entrances
located on two adjacent edges of a channel-corner
for increasing the coolant-flow fed into the narrow
channel without increasing the height of assembly
in order to enhance the capacity of cooling duty
for electronic chipsets parameter used that Rib
attack angle (α) = 45⁰ , Rib height/channel gap
ratio (e/B) = 1 mm/10 mm = 0.1 & Rib pitch/rib
height ratio (P /e) = 8 mm/1 mm = 8 and Rib
land/rib height ratio (l/e) = 1 mm/1 mm = 1. They
concluded that Effect of Re on spatially averaged
heat transfer over the skewed ribs roughened
surface to be evaluated for single side blow, single
upper-blow and two twin twin-blow conditions of
Res = Re u and Res = 2Reu. Among all the test
results, the twin-blow case of Res = Re u features
the worst heat transfer scenario while the Nu a
values in the twin-blow channel of Res = 2Reu are
in the range of 1.5–1.8 times of those counterparts
obtained in the sing-blow channels which measure
could be adopted for further heat transfer
augmentation in rib-roughened narrow channel.
9. Round tube with staggered WPT:
Sompol skull Ong [9] et al. The article
deals with thermal performance and flow
resistance characteristics in a turbular heat
exchanger fitted with WPT (Winglet Perforated
Tapes). Investigating the parameter of Re range of
4180-26,000, blockage ratio (Br) =0.15, prandtl
number (PR) =0.5, pitch rib ratio (ed) =10mm. It
gives better thermal efficiency of 13-15%.
10. SAH duct using 60⁰ inclined V shape
rib:
Rawat, jaurker [10] et al. experimentally
investigated heat transfer coefficient and thermal
efficiency by providing 60⁰ inclined V –SHAPED
ribs. They investigated the effect of heat transfer
and friction factor by using transverse, inclined,
V-continuous, V-discrete ribs on absorber plate in
solar air heater duct. Investigating the parameters
of Re range of 3,000-15,000, pitch duct ratio of
7.19-7.75, pitchroughness height =10mm, angle
of attack =60⁰, pitch rib ratio (ed) =0.0287.
Roughness of wall is heated with heat flux electric
heater while there running walls are insulated .It
was found that 60⁰ inclined rectangular ribs shows
better results than transverse ribs and thermal
performance of heat transfer is 1.82 times better
than smooth duct.
11. Turbulent flow through ribbed duct:
Priyank lahiya [11] et al. The paper mainly
focus on rib turbulators and heat transfer
enhancement and its design modification towards
enhancement of heat transfer and saving pumping
power. They used to find in a five different rib
ISBN-13: 978-1539669203
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©IIRDEM 201650

4. shapes such as square, rectangular, triangular,
circular and semi-circular. Holographic
interferometry is used to enhance heat transfer rate
in turbulent over square duct. Investigating the
parameters of Re range of 3,000-20,000, pitch
ratio (pe) =7, 8. Blockage ratio (edh) =8, 9. No
of ribbed walls=12, rib angle α=4⁰,10⁰. It was
found that heat transfer of roughened duct
produces more than that of smooth duct and also
while comparing square sectioned ribs produce
high enhancement in average Nusselt number than
circular rib of Reynolds number .
12. Circular duct with spiral rib:
Sagnik Pal, SujoyKumar Saha [12],
report that an circular duct with integral spiral rib
roughness and fitted with twisted tapes with
oblique teeth inserts have been presented. He used
Transverse rib roughness of two different rib
heights and rib pitches were investigated. The
twisted-tape with oblique teeth inserts in
combination with integral spiral rib roughness
performs significantly better than the individual
enhancement technique acting alone for laminar
flow through a circular duct. It was found that
spiral rib gives better thermal performance than
other relative gap widths.
13. Artificial roughened SAH duct with ribs:
Maidu Sharma, varun [13] et al.
experimentally investigated a comparison of solar
air heaters having different types of geometry of
roughness elements (continuous ribs) on absorber
plate. They experimentally investigated on
a)small diameter protrusion wire b)angle circular
rib c)wedged shaped rib d)rib grooved e)arc
shaped wire and they compared all the ribs with
an smooth duct. The parameters of range Re
3,000-21,000. Pitch roughness ratio=10mm, angle
of attack α=60⁰, rib height (0, 0181-0.053). It was
found that solar air heater having rib grooved and
arc shaped wire having better thermal
performance than others. It also concluded that
smooth duct having high heat transfer in lower
value of Reynolds number while compare with
other relative gap widths.
14. Rectangular duct with repeated ribs:
Arkan [14] et al. Computational fluid was
carried out to determine average heat transfer co-
efficient and friction factor for turbulent flow
through rectangular duct with ribs. The fluids in
the duct was air, and the average heat transfer co-
efficient were determined by measuring the
overall heat transfer co-efficient of duct. The
parameters of range Re of 3800-18,000. rib height
‘e”=0.5-2mm, rib pitch ‘p’-15mm, hydraulic
diameter of duct’d’-28.6mm. It was found that
ribs increase in both heat transfer and pressure
drop while comparing than smooth duct.
Conclusion: From this review, authors were
conducted many experiments on ribs by varying
size, angle, rib height, and roughness of
geometries. The authors are concluded that rib
will high heat transfer when the flow creates
turbulence in a boundary layer and also found that
smooth duct will give high heat transfer in lower
value of Reynolds number. The most efficient
way to dissipate the heat effectively by improving
surface roughness and use of ribs.
NOMENCLATURE
A- heat transfer area of channel
AR- Aspect ratio of channel (WH)
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Proceedings of ICRTE-2016
©IIRDEM 201651

5. D- Hydraulic diameter, m
e- Rib height, m
f- Friction factor
H- Channel height, m
h- Average heat transfer co-efficient,
(wm^2k)
I-Current, amp
K- Thermal conductivity of air (WMK)
L- Length of tested channel, m
m- Air mass flow rate (Kgs)
Nu- Nusslet number (hdk)
Re- Reynolds number
PR - Prandtl number
Br- blockage ratio
p- Pitch (axial length of rib cycle), m
Q- Heat transfer, W
T- Temperature, k
t- Thickness of rib, m
U- Mean velocity (ms)
Dp- pressure drop, pa
COMPARISON OF RIBS
S.N
O
AUTHOR RIB SHAPE TITTLE THERMAL
PERFORMANCE
1 Desai,
Yadav
Square duct W-type
shape rib
Gives Better thermal
performance in 60°.
2 Agarwal,
Gandhi
Rectangular duct
inclined discrete rib
Gives Better thermal
performance in pitch ratio of
7.5
3 Anilkumar SAH duct with V-
shape rib
Gives thermal performance of
3.82
4 Chandrasekhar
Bhatt
Nozzle rib in gas
turbine
High heat transfer at 45°
5 Mohammed rayed
facraqui
Rectangular rib in
SAH duct
High thermal performance of
1.82
6 Ponjet
promvongeet
Helical rib High thermal performance in
lower value of Reynolds
number
7 Sagnikpal Circular duct with
spiral rib
High thermal performance of
1.72
ISBN-13: 978-1539669203
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Proceedings of ICRTE-2016
©IIRDEM 201652

6. 8 Maidu Sharma ,
varun
Continuous rib in
SAH duct
High heat transfer at 45°
9 Priyank lahiya Rectangular duct
repeated ribs
Roughened duct gives high
transfer than smooth duct
10 s.w. chang Skew rib in narrow
channel
High heat transfer of 1.5-1.8
11 Arkan.k Rectangular duct
with inline,
staggered ribs
Inline rib gives high heat
transfer than staggered
Finally, I conclude that inline rib at 60° gives better thermal performance than other
relative gap widths. Because in an inline rib, the boundary layer which disrupts faster which creates
turbulence flow higher and velocity will be high in a duct, therefore heat transfer will be more.
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ISBN-13: 978-1539669203
www.iirdem.org
Proceedings of ICRTE-2016
©IIRDEM 201653