Shashi Kumar et al.

2023, 11:4 International Journal of Science,

ISSN (Online): 2348-4098 Engineering and Technology
ISSN (Print): 2395-4752
An Open Access Journal

CFD Analysis of Tubular and Sector-By-Sector

Helical Coil Heat Exchanger
M.Tech Scholar Shashi Kumar Keshri, Prof. Sujeet Kumar Singh
Department of Mechanical Engineering, PCST Bhopal

Abstract- A heat exchanger may be defined as an equipment which transfers the energy from a hot fluid to a
cold fluid, with maximum rate and minimum investment and running cost. The rate of transfer of heat
depends on the conductivity of the dividing wall and convective heat transfer coefficient between the wall
and fluids. The heat transfer rate also varies depending on the boundary conditions such as adiabatic or
insulated wall conditions. Heat exchange between flowing fluids is one of the most important physical
processes of concern, and a variety of heat exchangers are used in different type of installations, as in process
industries, compact heat exchangers nuclear power plant, HVACs, food processing, refrigeration, etc. The
purpose of constructing a heat exchanger is to get an efficient method of heat transfer from one fluid to
another, by direct contact or by indirect contact.

Keywords- Tubular, sector-by-sector helical coil heat exchanger, heat transfer

I. INTRODUCTION pipe placed concentrically inside another pipe

having a greater diameter. The flow in this
configuration can be of two types: parallel flow and
Tubular heat exchangers are built of mainly of
counter-flow. It can be arranged in a lot of series and
circular tubes although some other geometry has
parallel configurations to meet the different heat
also been used in different applications. This type of
transfer requirements. Of this the helically arranged
construction offers a large amount of flexibility in
stands out as it has found its place in different
design as the designing parameters like the
industrial applications.
diameter, length and the arrangement can be easily
modified. This type is used for liquid-to-liquid (phase
As this configuration is widely used, knowledge
changing like condensing or evaporation) heat
about the heat transfer coefficient, pressure drop,
transfer.
and different flow patterns has been of much
importance. The curvature in the tubes creates a
Again, this type is classified into shell and tube,
secondary flow, which is normal to the primary axial
double pipe and spiral tube heat exchangers.Heat
direction of flow. This secondary flow increases the
exchange between flowing fluids is one of the most
heat transfer between the wall and the flowing fluid.
important physical processes of concern, and a
And they offer a greater heat transfer area within a
variety of heat exchangers are used in different type
small space, with greater heat transfer coefficients.
of installations, as in process industries, compact
Study has been done on the types of flows in the
heat exchangers nuclear power plant, HVACs, food
curved pipes, and the effect of Prandtl and Reynolds
processing, refrigeration, etc. The purpose of
number on the flow patterns and on Nusselt
constructing a heat exchanger is to get an efficient
numbers. The two basic boundary conditions that
method of heat transfer from one fluid to another,
are faced in the applications are constant
by direct contact or by indirect contact. The heat
temperature and the constant heat flux of the wall.
transfer occurs by three principles: conduction,
convection and radiation. The double pipe or the
tube in tube type heat exchanger consists of one

© 2023 Shashi Kumar et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the
original work is properly credited.
Shashi Kumar et al. International Journal of Science, Engineering and Technology, 2023, ,11:4

Table 1: Operating and Geometrical parameters used

for CFD analysis (Abu-Hamdeh et al. (2020)
Operating and Geometrical Value / Range
parameters
Velocity of fluid, u 1.6-3.8 m/s
Temperature of cold water, Tc 283.15 K
Temperature of hot water, Th 353.15 K
Pitch, p 20 mm
Height of coil, H 80 mm
Fig. 1 Double pipe helical coil
Diameter of inner tube, di 6 mm
II. RESEARCH METHODOLOGY Diameter of outer tube, do 12 mm
Sector angle 30-150o
Computational domain
The details of the heat exchangers and their
geometrical variables are shown in Fig. 2. As it can Governing differential equations
be seen from this figure, these helical coil heat Continuity equation
exchangers are made from two sectors that are
connected via one of their plane surfaces thus; they
are called sector-by-sector heat exchangers. Indeed
the heat exchanger is divided into two parts using a (1)
spiral plate. According to Fig. 2Ɵ is the sector angle. Momentum Equation
Thus, the heat exchanger involves two sectors and
the water flows through the each sectors. Therefore,
a sector consists of warm water and the other
consists of the cold water.
(2)
Energy equation

(3)
Boundary Condition
On all the walls of the coil, no-slip boundary
conditions were assigned. At the inlet, uniform
velocity with an inlet temperature of cold fluid 300 K
and at the exit, invariable pressure (atmospheric
pressure) boundary conditions were assigned. All the
other edges were assigned as walls with insulated
boundary conditions, as shown in Fig. 3.3. The outer
Fig. 2 Schematic of computational domain
side wall was assumed to be adiabatic.

Fig. 3 Computational domain for CFD

Fig. 4 Boundary condition for CFD analysi

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Shashi Kumar et al. International Journal of Science, Engineering and Technology, 2023, ,11:4

CFD Modelling
Nusselt number
Commercially available ANSYS FLUENT v 15.0 was
the CFD software employed to solve the concerned 120
general differential equations numerically. This
software numerically simulates using finite element
100
method.

III. RESULTS AND DISCUSSION

80

Temperature Profile 60
In a helical coil tube heat exchanger, temperature
variation refers to the changes in temperature that 40
occur as a fluid flow through the coils of the heat
exchanger. This variation can occur both along the
length of the coil and across the cross-sectional area 20
of the coil.The flow rate of the fluids (hot and cold)
through the coil affects how much heat is transferred 0
and how quickly the temperature changes. Higher 10000 20000 30000 40000
flow rates can lead to smaller temperature
Tubular helical heat exchanger 30o 90o 150o
differences along the coil.The initial temperatures of
the hot and cold fluids entering the heat exchanger
impact the temperature difference driving the heat
transfer. A larger initial temperature difference Fig. 6: Variation of Nusselt number at different sector
usually results in greater temperature variation along angle
the coil.

Effect of Sector Angle on Friction Factor

Friction factor
0.5

0
Fig. 5: Temperature profile in sector-by-sector coil 10000 20000 30000 40000
type heat exchanger Tubular helical heat exchanger

Effect of Sector Angle on Nusselt number 30o

Effect of sector angle on Nusselt number is shown in 90o
Fig 6. The horizontal x-axis represents Reynolds
number and y-axis represents Nusselt number. It is 150o
seen that increase in sector angle results in increase
in Nusselt number and it is maximum at 150o. This Fig. 7: Variation of Friction factor at different sector
may be due to the fact that at higher values of sector angle
angle, reattachment of free shear layer might not
occur and rate of heat transfer enhancement is not Effect of sector angle on friction factor is shown in
proportional to that of friction factor. Fig. 7. The horizontal x-axis represents Reynolds
number and y-axis represents friction factor. It is
seen that increase in sector angle ratio results in
increase in friction factor and it is maximum at 150o.
This may be due to the fact that at higher values of

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 Shashi Kumar et al. International Journal of Science, Engineering and Technology, 2023, ,11:4

sector angle, pumping power is required more.The area of the coil's flow passage decreases. This
pressure drop across the heat exchanger is closely reduction in cross-sectional area can lead to
related to the friction factor. As the fluid flows increased flow velocity, especially when the same
through the narrower cross-sectional area of the coil flow rate is maintained. Higher flow velocity
with a higher sector angle ratio, it encounters increases the likelihood of fluid friction against the
increased resistance, leading to a greater pressure coil's walls, resulting in a higher friction factor.
drop. This pressure drop represents the energy loss
due to fluid friction. The observation that the friction
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