Effect of Wavy (Corrugated) Twisted Tape Inserts on Heat Transfer in a double Pipe Heat Exchanger

NOVATEUR PUBLICATIONS
INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT]
ISSN: 2394-3696
VOLUME 2, ISSUE 1 JAN-2015
1 | P a g e
Effect of Wavy (Corrugated) Twisted Tape Inserts on Heat Transfer
in a double Pipe Heat Exchanger
Mr. A. S .Kurhade
Department of Mechanical Engineering, GSMCOE, University of Pune, India
Prof. M. M. Dange
Department of Mechanical Engg. Faculty of Engineering, GSMCOE, University of Pune, India
Prof. D. B. Nalawade
Department of Mechanical Engineering, Faculty of Engineering, VIIT, University of Pune, India
Abstract
In the present work heat transfer and friction factor properties were experimentally investigated by using copper
wavy (corrugated) twisted tape inserts. The turbulent flow was created by inserting the wavy twisted tape inserts
into the inner tube of heat exchanger creating high rate of turbulence in pipe, which results in increasing heat
transfer enhancement and pressure drop. The tape consists of the corrugations and the twisting with various twist
ratios (TR=10.7, 8.5, 7.1). The length and width of insert was 1 meter and 14 mm respectively. The outer tube of
heat exchanger is made up of mild steel with outside diameter 0.0198 m & 0.0142 m inside diameter and the inner
tube is made up of copper with 0.038 m outside diameter and 0.032 m inside diameter. The length of pipe in pipe
heat exchanger is 1.4 m. The bulk mean temperatures at various positions are used for different flow rate of water.
From the obtained results the new Correlations for Nusselt number and friction factor are developed for twisted
tape inserts. The Reynolds number is varied from 5000 to 17000. The results of varying twists in wavy twisted
tape inserts with different pitches have been compared with the values for the smooth tube. It showed that the
highest heat transfer rate was achieved for the wavy twisted tape with twist ration 7.1. The Nusselt number value
increased by 172 % and friction factor value increased by 32.11% as compared to the smooth tube values.
Keywords - Heat transfer, heat exchanger, wavy twisted tape, turbulent, pressure drop, friction factor,
Introduction
In heat exchanger, the enthalpy is transferred between two or more fluids, at different temperatures. The use of
heat exchangers are in various industrial processes for heating and cooling applications such as air conditioning
and refrigeration systems, heat recovery processes, food and dairy processes, chemical process plants etc. The
major challenge in designing a heat exchanger is to make the equipment more compact and achieve a high heat
transfer rate using minimum pumping power. Techniques for heat transfer augmentation are relevant to several
engineering applications. In recent years, the high cost of energy and material has resulted in an increased effort
aimed at producing more efficient heat exchange equipment. Sometimes there is a need for miniaturization of a
heat exchanger in specific applications, such as space application, through an augmentation of heat transfer.
Furthermore, as a heat exchanger becomes older, the resistance to heat transfer increases owing to fouling or
scaling. These problems are more common for heat exchangers used in marine applications and in chemical
industries. In some specific applications, such as heat exchangers dealing with fluids of low thermal conductivity
and desalination plants, there is a need to increase the heat transfer rate. The heat transfer rate can be improved by
introducing a disturbance in the fluid flow thereby breaking the viscous and thermal boundary layer. However, in
the process pumping power may increase significantly and ultimately the pumping cost becomes high. Therefore,
to achieve a desired heat transfer rate in an existing heat exchanger at an economic pumping power, several
techniques have been proposed in recent years and are discussed under the classification section. The heat transfer
enhancement techniques are performed in widespread applications. Those methods are, for instance, the insertion
of twisted strips and tapes, the insertion of coil wire and helical wire coil and the mounting of turbulent decaying
swirl flow devices in several heat exchangers. The results of those studies have been shown that although heat

ISSN: 2394-3696
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transfer efficiencies are improved, the flow frictions are also considerably increased. In this report the various
wavy twisted tapes are used for heat transfer enhancement having various twist ratios. The strips are expected to
induce a rapid mixing and a high turbulent and longitudinal vortex flow like a delta wing, of course, resulting in an
excellent rate of heat transfer in the tube.
Experimental Set-Up
Fig. 1 The schematic diagram of experimentation
Fig. 2 Actual photograph of experimentation

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The experimental set up and the various measuring devices were shown in figure. It consisted of tube in tube type
heat exchanger. The material of inside tube was of Copper and outside tube was of Mild Steel. The thermocouples
were used to measure the inlet and outlet temperature of cold and hot water. Here four thermocouples were used;
two at the inlet and two at the outlet of hot and cold water respectively. Rota meters were used to measure
the flow rate at inlet of cold and hot water. Two centrifugal pumps were used to circulate the cold and hot water.
Two tanks were used for storing the hot water and cold water. Electric heater was attached to the hot water tank
having capacity of 1500 watt. Inverted U-tube manometer was used to measure the pressure difference between
inlet and outlet of test section of hot fluid the velocity of flow through inserted tube was measured by using current
meter. The control valves and bypass valves were provided at inlet of both the rota meters.
Procedure
In the experiment, initially the water tank was filled with cold water and maintained its temperature up to 80 0
C by
using water heater. Then, this hot water was flowed through the rota meter by opening the flow control valve with
help of hot water pump and through the inner pipe of heat exchanger. The cold water from the cold water tank was
allowed to enter the heat exchanger through rota meter by flow control valve & cold water pump. Adjust the flow
rate of cold water at 100 LPH and made it constant during whole experiment. The flow rate of hot water was
adjusted at 300 LPH and kept it constant. When the steady state was reached, the temperatures of the inlet and
outlet of the cold and the hot waters were recorded and pressure drop across the test tube was measured for plain
tube without inserts. Thereafter repeat same procedure with wavy twisted tapes having twist ratio (TR=10.7, 8.5,
7.1) for various flow rates of hot water like 400, 500, 600, 700, 800, 850, 900 & 950 LPH. The figure 3 shows the
terminology of wavy twisted tape and figure 4, 5, 6 shows the wavy tape inserts with twist ratio 10.7, 8.5, 7.1
respectively.
Fig. 3 Terminology of twisted tape
Fig. 4 Wavy corrugated twisted tape with TR – 10.7

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Specifications of inserts:
1. Material = Copper
2. Width of twisted tape (W) = 14 mm
3. Twist ratio (TR) = 10.7, 8.5, 7.1.
4. Length of insert = 1000 mm
5. Thickness of inserts = 2 mm
6. Wave-width (WW) = 10 mm
7. Depth of wave = 10 mm
Sample Calculations
The Properties of hot water and cold water are calculated at their bulk mean temperature,
Tbh =
2
T+T h2h1
(1)
Tbc =
2
T+T c2c1
(2)
Tbh and Tbc are bulk mean temperature of hot & cold water. Th1 & Th2 and Tc1 & Tc2 are inlet and outlet
temperature of hot & cold water respectively.
Hot water heat transfer rate,
Qh = mh × Cph × (Th1-Th2) (3)
Cold water heat transfer rate,
Qc = mc × Cpc × (Tc2-Tc1) (4)
mh & mc are the mass flow rate of hot and cold waters. Cp is the specific heat coefficient of water. (Th1-Th2) and
(Tc2-Tc1) are the present temperature difference between inlet and outlet cold water and temperature difference of
inlet and outlet hot water, respectively.
An average heat transfer rate between hot and cold waters and the convection heat transfer between copper surface
and hot fluid flow, can be written as,
Qavg. =
2
Ch QQ +
(5)
Qavg. = TmAsU ∆×× (6)
∆Tm =
( )
( )2
1
ln
21
T
T
TT
∆
∆
∆−∆
(7)
∆T1 = Th1 – Tc2
∆T2 = Th2 – Tc1

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As , U & ∆Tm is the surface area of tube, overall heat transfer coefficient & Logarithmic mean temperature
difference respectively.
Nusselt Number of cold water flowing through the annular space is given by,
Nuo = 0.023(Reo) 0.8
(Pr) 0.3
(8)
Reo =
µ
ρ hoDU
(9)
Dh = Di - do
Continuity equation, mc = ρAoUo
Heat transfer coefficient (h0) of cold water flowing through the annular space is given by,
Nuo =
K
hoDh
(10)
ho =
h
o
D
KNu
Heat transfer coefficient of hot water (hi),
oi hhU
111
+=
(11)
Nusselt Number (Experimental) of hot water flowing through the tube,
Nui =
K
iidh
(12)
Theoretical Nusselt Number of hot water flowing through the tube is given by (Dittus Boelter equation).
Nui = 0.023(Rei) 0.8
(Pr) 0.3
(13)
Experimental Friction Factor is calculated by,
ghP ρ=∆
i
i
d
UfL
P
2
2
ρ
=∆
2
2
i
i
LU
hgd
f =
(14)
Theoretical Friction Factor f can be written as,






















++×=
33.0
6
Re
10
5010055.0
i
f (15)
Result and discussion
After the experimental study, the Nusselt numbers and friction factors were calculated for plain tube and tube with
wavy tape inserts. These results were compared with the correlation of Dittus and Boelter for Nusselt number &

ISSN: 2394-3696
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John Nikuradse for friction factor. Figure 7a.shows the graph of Nusselt number Vs Reynolds number for plain
tube. It is found that there is linear behavior of Nusselt number along Reynolds number. Nusselt number is a
function of Reynolds number. Figure 7b.shows the graph of friction factor Vs Reynolds number for plain tube. The
friction factor is inversely proportional with Reynolds number.
Fig. 7a Nusselt number Vs Reynolds number Fig. 7b Friction factor Vs Reynolds number
Fig. 8 Nusselt number Vs Reynolds number for TR=10.7, 8.5, 7.1
Figure 8 shows the variation of Nusselt number with Reynolds number at various twist ratios (TR=10.7, 8.5,
7.1). This figure concludes that the Nusselt number increases with increase in Reynolds number. Therefore heat
transfer rate is more with higher Reynolds number. Here Nusselt number is more for the twisted tape with lesser
twist ratio (TR – 7.1) for particular Reynolds number compared with other twisted tapes. So highest heat transfer
rate was obtained for lesser twist ratio.

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Fig. 9 Friction Factor Vs Reynolds number for TR=10.7, 8.5, 7.1
Figure 9 shows the variation of friction factor with Reynolds number. It was found that the friction factor become
greater as the twist ratio decreased. The value of friction factor is more for the wavy twisted tape insert having
twist ratio 7.1 as compared with other inserts. The friction factors for the case of the insert having twist ratio 7.1,
8.5 & 10.7 were 2.00, 1.47 and 0.147 times over the plain tube respectively.
Conclusions
By using wavy (corrugated) twisted tape inserts the highest heat transfer rate was achieved for twist ration 7.1. In
comparison with plain tube all wavy twisted tape inserts would significantly enhance the heat transfer rate. The
more twist increased the heat transfer and decreased the friction factor. From this experimental study the results
can be concluded as follows,
1) For Reynold number range 5000 to 17000, the Nusselt number for wavy twisted tape insert with twist ratio
10.7, 8.5 and 7.1 was found to be 75.75 %, 157 % and 172 % respectively.
2) The Friction factor is increased approximately by 9.4 %, 22.44 % and 32.11 % with twist ratio 10.7, 8.5
and 7.1 respectively.
Nomenclatures
As Lateral surface area of tube, m2
Re Reynolds number
Cp Specific heat, J/Kg K V Mean velocity of water
f Friction factor L Length of inner tube
h Heat transfer coefficient, W/m2
K ν Kinematic viscosity of water
k Thermal conductivity, W/mK ρ Density of water
Nu Nusselt number Pr Prandle number
∆P Prassure drop
References
[1] Veysel Ozceyhan, Sibel Gunes, Orhan Buyukalaca and Necdet Altuntop, “Heat transfer enhancement in a tube
using circular cross sectional rings separated from wall”, Applied energy 85 (2008) 988 – 1001
[2] Naga Sarada S., Kalyani K. Radha, A.V.S.Raju, “Experimental Investigation in a Circular Tube to Enhance
Turbulance Heat Transfer Using Mesh Inserts”, ARPN Journals of Engineering & Applied Science (2009)
[3] Piroz Zamankhan, “Heat transfer in counterflow heat exchangers with helical turbulators”, Commun Nonlinear
Sci Numer Simulat 15 (2010) 2894–2907
[4] Mr.Kumbhar D.G., Dr. Sane N.K.,”Heat Transfer Behavior In A Tube With Conical Wire Coil Inserts”.

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[5] Somsak Pethkool, Smith Eiamsa-ard, Artit Ridluan and Pongjet Promvonge, “Effect of Louvered Strips on
Heat Transfer in a Concentric Pipe Heat Exchanger”, The 2nd Joint International Conference on “Sustainable
Energy and Environment (SEE 2006) 21-23 November 2006, Bangkok, Thailand
[6] Paisarn Naphon , Effect of coil-wire insert on heat transfer enhancement and pressure drop of the horizontal
concentric tube,
[7]S.K. Saha, A. Dutta, S.K. Dhal, Friction and heat transfer characteristics of laminar swirl flow through circular
tubes fitted with regularly spaced twisted-tape elements, International Journal of Heat and Mass Transfer 44
(2001) 4211–4223.
[8] R. Sethumadhavan, M.R. Rao, Turbulent flow heat transfer and fluid friction in helical-wire-coil-inserted tubes,
International Journal of Heat and Mass Transfer 26 (1983) 1833–1845.
[9]Sivashanmugam .P and P.K. Nagarajan, 2007. “Studies on heat transfer and friction factor characteristics of
laminar flow through a circular tube fitted with right and left helical screw-tape inserts”, Experimental Thermal
and Fluid Science, Vol. 32, No. 1, pp. 192-197.
[10] Shah, R.K., Joshi, S.D., 1987. Convective heat transfer in curved ducts. In: Kakac, S., Shah, R.K., Aung, W.
(Eds.), Handbook of Singlephase Convective Heat Transfer. Wiley Interscience, New York, pp. 5.1–5.46.Eiamsa-
ard.
[11] Patil A.G, February 2000, “Laminar flow heat transfer and pressure drop characteristics of power-law inside
tubes with varying width twisted width inserts”, ASME Transactions, Vol. 122, pp. 143-149.
[12] L.Wang, B. Sund, “Performance comparison of some tube inserts”, International communication Heat Mass
Transfer 29 (2002) 45–56.
[13] Pongjet Promvonge, “Thermal performance in circular tube fitted with coiled square wires”, 2007 Elsevier
Ltd.
[14] V. Ozceyhan, “Conjugate heat transfer and thermal stress analysis of wire coil inserted tubes that are heated
externally with uniform heat flux”, Energy Conversion and Management 46 (2005) 1543–1559.
[15] M.A. Akhavan-Behabadi, M.R. Salimpour, V.A. Pazouki, “Pressure drop increase of forced convective
condensation inside horizontal coiled wire inserted tube”. International Communications in Heat and Mass
Transfer 35 (2008) 1220e1226.
[16] K.N. Agrawal, A. Kumar, M.A.A. Behabadi, H.K. Varma, “Heat transfer augmentation by coiled wire inserts
during forced convection condensation of R-22 inside horizontal tubes”, International Journal of Multiphase Flow
24 (1998) 635–650.
[17] P.Promvonge, “Thermal performance in circular tube fitted with coiled square wires”. Energy Conversion and
Management49 (2008)980e987.
[18] Naphon P. “Effect of coil-wire insert on heat transfer enhancement and pressure drop of the horizontal
concentric tubes”. Int Commun Heat Mass Transfer 2006; 33(6):753–63.
[19] S. Gunes, V. Ozceyhan, O. Buyukalaca, The experimental investigation of heat transfer and pressure drop in a
tube with coiled wire inserts placed separately from the tube wall, Applied Thermal Engineering 30 (2010) 1719–
1725.

Effect of Wavy (Corrugated) Twisted Tape Inserts on Heat Transfer in a double Pipe Heat Exchanger

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