Analysis of Double Pipe Heat Exchanger With Helical Fins

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 08 | Aug -2017 www.irjet.net p-ISSN: 2395-0072
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ANALYSIS OF DOUBLE PIPE HEAT EXCHANGER WITH HELICAL FINS
Bandu A.Mule1, Prof.D.N.Hatkar2,Prof.M.S.Bembde3
1 ME student, Department of Mechanical Engineering, MGM’s COE, Nanded, Maharashtra, India.
2 Professor, Department of Mechanical Engineering, MGM’s COE, Nanded, Maharashtra, India.
3Professor, Department of Mechanical Engineering, TCOE, Nerul, Mumbai, Maharashtra, India.
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Abstract – In this present day double pipe heat exchanger
is the most common type of heat exchanger widely use in
oil refinery and other large chemical processes because it
suits high pressure application. To determine the
performance of double pipe heat exchanger, the hot fluid
has made to flow through inner tubes and cold fluid is flow
through the outer tubes. The main objective is to design
the DPHE with different angles of fins. & to study the flow
and temperature field inside the tubes. Also, attempts
were made to investigate the effects and heat transfer
characteristics of a DPHE for six different inclination of
fins namely 0 , 5 , 10 T
of DPHE has made by using CATIA V5 and meshing is
generated by using hyper mesh. The flow and temperature
field inside the tube have studied using ANSYS FLUENT
R18.0. The work determines with better enhancements in
heat transfer rate and overall heat transfer coefficient
using helical fins.
Key Words: Helical fins, overall heat transfer coefficient,
heat transfer rate, mass flow rate, CFD.
1. INTRODUCTION
The heat exchanger is a device used to transfer the heat
from the hot fluid to cold fluid with maximum rate and
minimum investment. The heat exchanger is an important
device in various thermal systems for e.g. condenser and
evaporator in refrigeration systems, boiler & condenser in
steam power plants etc. The heat exchanger has wide
variety of industrial applications such as process
industries, chemical industries, food industries etc. Now
there is need of the compact heat exchangers to give
required heat transfer rate with minimum space
requirement. The helical fins on the inner tube increase
the area available for the heat transfer and the helical fins
on inner tube increases the turbulence. With helical fins at
larger pitch, the efficiency of the heat transfer
enhancement however is rather low when the total length
of heat exchanger is fixed. At high Reynolds number,
pressure drop will increase sharply if the helical pitch
decreases. Due to this reason the heat transfer
enhancement with helical fins is more suitable at low
Reynolds number. The worldwide researchers are making
hard efforts to find out suitable alternatives for heat
exchangers with different geometry and varying
parameters which effects on performance of heat
exchanger. Now days helix fins has became blessings for
researchers. Balarama Kundu et al. [1] had
experimentation on beneficial design of shell and tube
heat exchangers for attachment of longitudinal fins with
trapezoidal profile. In this experimentation, the
rectangular and trapezoidal fin shapes longitudinally
attached to the fin tubes. The results show that the heat
transfer rate was lesser than the rectangular cross section
keeping the outer shell diameter is a constant along with
all other constraints of a heat exchanger. N. Sathiya
Narayanan et al. [2] had done modelling and simulation of
helical fluid flow through double start screw type heat
exchanger. In this experimentation efficient heat transfer
is achieved by increasing the area of heat transfer by
providing fin arrangement. The result shows that an
efficient heat transfer is achieved as heat transfer
coefficient is more. Shewale omkar M et.al. [3] have
performed experimental investigation of double pipe heat
exchanger with helical fins on the inner rotating tube. In
this analysis the Nusselt Number obtained from the
experimental results are higher than that of theoretical
values obtained from Dittus-Boelter equation. The helical
fins over the inner tube results into the increase in the
heat transfer area and reduction in the hydraulic diameter
of the flow channel. The result shows that the Nusselt
number for the inner tube with helical fins is 4 times
higher than that of the plain inner tube for stationary
condition. The Nusselt number at the speed 50 rpm and
100 rpm are 36 % and 64% more than that of stationary
inner tube. Vinous M Hameed et al. [4] have carried out an
experimental study of turbulent flow heat transfer and
pressure loss in a double pipe heat exchanger with
triangular fins. The working fluids were air flowing in the
annular pipe and water through the inner circular tube.
The results shows that the heat dissipation 3.815 to
5.405times than that of smooth tube. . In the lowest space
the average increment in nusselt number is about 98%
over the smooth tube heat exchanger. Yu et al. [5]
performed to compute the heat transfer and pressure drop
characteristics of tubes with internal wave-like
longitudinal fins. They conducted two cases for this work
were carefully examined, using air as a working fluid. For
the tube of type A, since the inner channel of the insertion
is not blocked, its flow cross-section area only differs
mildly from that without the insertion. While for the tube
of type B the cross-section of the inner tube is totally
blocked. The wave-like fins are within the annulus and
span its full width. There are total 20 waves. The outer
tube was electrically heated. Pressure taps were no

uniformly distributed in 13 cross-sections along the test
tube axis. Results showed that the wave-like fins enhance
heat transfer significantly with the blocked case by 36%
higher than that of unblocked tube. Sameer H. Ameen et al.
[6] has constructed a model with parabolic fins fixed over
the outer surfaces of its inner pipe with different
inclination angles from copper alloy. They carried out the
numerical work using ANSYS14.0 and conclude that local
heat convection for parabolic fin heat exchangers is 2.42
times greater than pipes without fins.
1.1 Materials selection
Heat Exchanger
The selection of material is the first step while designing a
heat exchanger. There are so many materials available at
market for double pipe heat exchanger like copper,
stainless steel, aluminum, etc. However, the process
temperature and pressure dictates the choice of the
material. As we are dealing with hot fluid there will be
chances of development of thermal stresses, so copper and
stainless steel are selected. As copper is having high
thermal conductivity it is selected for inner tube and
stainless steel for annulus. The brazing material used in
stainless steel exchangers is a nickel based alloy with
appropriate melting and welding characteristics.
Table -1: Thermal Properties of water
Sr.no. Property Water(hot) Water(cold)
1 C, J/kg K 4179 4179
2 ρ k / 3 997.1 997.1
3 k, W/m K 0.605 0.605
4 u, m2/s 0.001 0.001
2. Computational fluid dynamic procedure
2.1 Geometry and computational fluid domain:
The schematic diagram of computational fluid domain is
as shown in fig.1.
(a)
(b) (C)
(d) (e)
(f) (g)
Fig.1 (a) Geometry of Double pipe heat exchanger, (b)
Computational fluid domain
2.2 Grid Generation
Fig. 2 Discretized computational domain
2.3 Setting of boundary condition and solving
The inlet boundary conditions are defined as cold fluid
velocity flowing though outer pipe and hot fluid velocity
flowing though inner pipe in counter flow.
Table2: Boundary Conditions
Quantities Boundary Conditions
Working fluid Water Water
Inner pipe
(hot fluid)
Hot inlet (water)
Velocity Temperature
0.1472 m/s 550C
Outer pipe
(cold fluid)
Cold inlet (Water)
Velocity Temperature
0.05859 m/s to 0.5859 m/s 280C

2.4 Post processing
The variables such as temperature, velocity, water are
represented in the form of vectors, contours which are
extracted from post processing tool.
3. Experimental set up
3.1 Fabrication:
The experimental set up fabricated as per design of heat
exchanger. Four temperature indicators are used to
measure inlet and outlet temperatures. Two pumps with
two flow controlling valves each and a flow meter, two
tanks to store the water. The system line diagram is shown
in fig.3
Fig. 3 Line diagram of set up
3.2 Actual set up photo
4. Data processing
4.1 Analysis of heat exchanger
1. According to first law of thermodynamics, heat transfer
rate from hot fluid is equal to cold fluid. It is given by,
 Hot fluid heat transfer rate Qh= mh*Cph*(Thi-Tho)
 Cold fluid heat transfer rate Qc= mc*Cpc*(Tco-Tci)
Where, mh and mc are the mass flow rates of hot and cold
fluid respectively, Cph and Cpc are the specific heats of hot
and cold fluid respectively, Thi and Tci are hot and cold
inlet temperatures, Tho and Tco are hot and cold outlet
temperatures. Then average of both of them is taken for
further calculation as shown below,
Qavg = (Qh + Qc)/2
2. Logarithmic mean temperature difference (LMTD) is
calculated by using formula,
LMTD (∆Tlm) =
( – ) ( – )
( – ) ( – )
3. The surface area is calculated as
As= Π*D *L+ LNH
The overall heat transfer coefficient
is calculated by using formula,
Qavg= U*As*∆Tlm
5. Results and Discussion
Effects of helix angles of fin in the base fluid on
thermophysical properties of water and different
parameters like heat transfer rate, overall heat transfer
coefficient are discussed in this chapter.
Table 3: For 0.017 Kg/sec
Table 4: For 0.034 Kg/sec
1, 2 - Storage tanks
3, 4 – Pumps
5, 6 - Ball valves
7, 8 – Rota meters
9 -Stainless steel tube
10 - Copper tube
11 - Control panel
Fins
inclin
ation
angle
Tco
CFD
Tco
EXP
Heat
Transfer
(W)
CFD
Heat
Transfer
(W)
EXP
Overall Heat
Transfer
Coefficient
(W/m2 OC)
CFD EXP
39.94 39 462.86 747.06 236.43 357.63
39.97 500.74 390.88
40.02 40 563.02 818.55 441.70 636.82
40.22 570.14 450.01
40.43 41 655.91 854.14 523.44 685.39
40.78 582.95 467.99
Fins
inclin
ation
angle
Tco
CFD
Tco
EXP
Heat
Transfer
(W)
CFD
Heat
Transfer
(W)
EXP
Overall Heat
Transfer
Coefficient
(W/m2 OC)
CFD EXP
36.43 37 649.86 996.5 293.26 451.3
36.89 696.84 511.26
36.94 37 775.13 1067.64 571.32 763.9
37.14 800.05 593.79
37.35 39 829.83 1138.86 621.51 878.2
37.70 825.67 619.84

5.1 Effect on overall heat transfer coefficient
Graph 5.1 Helix angle Vs Overall Heat Transfer Coefficient
(U)
From CFD analysis, it shows that the mass flow rate
increases then overall heat transfer coefficient increases.
The graph shows the effect of helix angle on overall heat
transfer coefficient for five flow rate
5.2 Effect on heat transfer rate
Graph 5.2 Helix angle Vs Heat Transfer Rate (Q)
From CFD analysis, it shows that the mass flow rate
increases then heat transfer rate increases. The graph
shows the effect of helix angle on heat transfer rate for five
flow rate. From CFD analysis of different helix angle of
fins it is found that increase in helix angle then increases
the overall heat transfer coefficient. Also, the mass flow
rate increases the values of U.
(a) 0 angle (b) angle
(c) 1 angle (d) 15 angle
(e) 2 angle (f) 25 angle
Fig.5.3 Temperature distribution diagrams
The figure5.3
, 15 , and 20 and 25 Diagrams are for
the first reading of each helix angle. As hot flow rate is
constant throughout and cold flow rate is varied from 1
LPM to 5 LPM.
6. Conclusions
Analysis of different helix angles of fins for a double pipe
heat exchanger with the help of ANSYS FLUENT R18.0 is
studied. From those angles experimental study on three
angles ( ) is performed. The thermal performance
parameter overall heat transfer coefficient has been
determined. Some of main conclusions of the present work
are noted below.
1. From CFD analysis it is observed that increase in
heat transfer rate (1494.75 W to1920.05 W) and overall
heat transfer coefficient (734.58 W/m2 OC to 1570.46 W/m2
OC W) it
decreases
2. From CFD analysis it is observed that increase in
helix fins gives promising enhancement in heat transfer
rate.
E
o
0
2000
0ͦ 10ͦ 20ͦ 25ͦ
OverallHeatTramnsfer
CoefficientW/m20c
Helix angle
Helix angle Vs Overall Heat
Transfer Coefficient
1 lpm
CFD
1 lpm
EXP
2 lpm
CFD
2 lpm
EXP
3 lpm
CFD
3 lpm
EXP
4 lpm
CFD
4 lpm
EXP
0
500
1000
1500
2000
2500
0ͦ 5ͦ 10ͦ 15ͦ 20ͦ 25ͦ
HeatTransferRate(W)
Helix Angle
Helix Angle Vs Heat Transfer Rate
1 lpm
cfd
1 lpm
exp
2 lpm
cfd
3 lpm
cfd
3 lpm
exp
5 lpm
cfd
5 lpm
exp

4. From these analysis it indicates that heat transfer
rate is better for helical fins in double pipe heat
exchanger.
FUTURE SCOPE
The conventional method used for the design and
development of double pipe heat exchanger are expensive
.CFD provide alternative to cost effectiveness speedy
solution to DPHE design and optimization. The extension
of this work can be done by using Computational Fluid
Dynamics (CFD) analysis for knowing heat transfer rate
over the helical fins in DPHE.
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