Page 1 of 12
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online:https://ejbss.org/ P a g e | 1352
ENHANCEMENT OF HEAT TRANSFER COEFFICIENTS
OF HEAT EXCHANGER
PRABAKARAN .S
PG Student,
PRIST Deemed to be University, Thanjavur
Abstract – A shell and tube heat
exchanger are the best common type of
heat exchanger in oil refineries and other
large chemical process industries and is
suited for higher-pressure applications.
The designs of thermal energy systems
have crossed many ways in the past few
decades which lead to some improvements
in performance. Even though various
techniques were applied to enhance heat
transfer, there is still bright scope for the
improvement of the performance. For
many decades, efforts have been done by
many researchers to enhance heat transfer
of heat exchangers and finally reported a
reasonable increase in heat transfer
characteristics of nanofluids when
compared to the respective base fluids.
Most of the research works have been
carried out for different nanofluids like
CuO/Water, Al2O3/water, TiO2/Water,
Graphite/water, Ethylene Glycol/Water,
Silicon Nitride/Water and Carbon
nanotube/Water for the study of heat
transfer enhancement in bare tube, twisted
tape and with coils separately.
An improvement in heat transfer co- efficient studied by using Graphite /water
& Al2O3/water nanofluids in shell and tube
heat exchanger increase at different
volume concentration of the nanoparticles
compared with water. We have taken up
these nanofluids and compared to find out
which fluid is having more heat transfer
enhancement at different concentrations
and flow rates in bare tube, twisted tape
with right and left twist. Hence this work
has been taken up for this work.
Keywords- Heat exchanger, shell and tube,
nano fluids
I.Introduction
The Shell and tube heat exchanger are an
important class of heat exchanger designs. In
oil refineries and other large chemical and
process industries this type of shell and tube
heat exchanger is mostly used and best is
suited for higher-pressure applications. As its
name implies, it consists of a shell (a large
pressure vessel) with number of tube made as
a bundle inside it. One fluid flows inside the
tubes and another fluid runs over the tubes
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European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online:https://ejbss.org/ P a g e | 1353
(through the shell) to transfer heat between
these two fluids. The number of tubes
assembled called a tube bundle and may have
several pairs of tubes namely plain,
longitudinally finned etc.
In this heat exchanger two fluids flow at
different temperatures. One fluid flows into
the tubes and the other fluid flows inside the
shell (the shell side).
Transfer of heat occurs from one fluid to
the other through the walls of the tube, either
from shell side to tube side or vice versa. The
fluids may be either liquids or gases on the
shell side or the tube side. To improve the
transfer heat effectively, a large heat transfer
area should be used, leading to more number
of tubes may be used. In this way, waste heat
can be put to use. This is one of the most
efficient ways to conserve energy. There are
many variations in actual practice on the shell
and tube design. Typically, the ends of each
tube are connected to water chambers
(sometimes called water boxes) through holes
in tube sheets. The tubes may be straight or in
the shape of ‘U’ called U-tubes.
The Pressurized water reactors in nuclear
power plants and steam generators which are
otherwise called as large heat exchangers, are
two pass – shell and tube heat exchangers
which have U tubes. These exchanger are
being utilized to boil water which are recycled
from a surface condenser into steam to drive a
turbine to produce power. Most of the shell
and tube heat exchangers are 1, 2, or 4 pass
designs on the tube side. The important use of
this multi pass is to make the fluid passes
through the tubes and shell into number of
times. In a single pass heat exchanger, the fluid
goes from one end of the tube and comes out
through the other.Surface condensers in power
plants generally have single pass straight-tube
heat exchangers. Two and four pass designs
are common because the fluid enters and exits
on the same side. This makes construction
much simpler.
The objective of the project work is to
investigate the heat transfer characteristics of
water/water, Graphite/water and Al2O3/water
nanofluids in a horizontal 1-2 shell and tube
heat exchanger. The behavior of Nusselt
number, thermal conductivities, viscosities,
specific heat capacities, heat transfer
coefficients of various nano fluids such as
Graphite /water and Al2O3/water are to be
studied.
Using suitable inserts like left twisted
tape, right twisted tape 1-2 Shell and Tube heat
exchanger, suitable nanofluids for heat transfer
applications that have more amount of heat
transfer enhancement need to be identified.
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European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online:https://ejbss.org/ P a g e | 1354
II.Experimental Setup
The experimental setup has pump,
water storage tank of capacity 175 lit,
water heater, shell and tube heat
exchanger and thermocouples at inlet and
outlet to measure the temperature. The
thermocouples were calibrated by PT100
type and the error in them is less than 0.1
LC. The thermocouples 1 and 2 are used
to measure the inlet temperature and the
exit temperature of the nano fluid and on
the contrary the thermocouples 3 and 4
measure the inlet temperature of the base
fluid. In order to get very good
experimental results, first of all equipment
is made stable by passing the water
through the shell as well as the tube side
of the heat exchanger.
The experimental setup consists of a
shell with 51 mm inside diameter and the
tube bundle consisting of 6 tubes with 8
mm outside diameter, 1mm thickness and
518 mm length and the tube pitch is 8
mm. The baffle spacing is 15% and 129.5
mm respectively. The heat exchanger as
well as the pipe is strongly wound by a
thermal insulation tape. Two series of
solution are prepared such as aluminium
oxide-water and graphite-water where
water flows through the shell side in both
the cases. To prepare stable nanofluids,
ultrasonic vibrations were made to pass
through it to prevent the agglomeration of
the nanoparticles.The nanofluids are
prepared with different particle
concentration such as 0.1%, 0.2%, 0.3%
respectively. It is done to investigate the
effect of the nanoparticles concentration
on the heat transfer performance of the
nanofluids.
Fig.1 Schematic diagram of experimental
Setup
Twisted Tapes:
To develop flow hydro-dynamically,
twisted tapes are inserted in the heat transfer
test tube. The twisted tapes were tested in
experiments with twist ratio (y/D = 3.0) and
two different twists (Left twist and right twist)
with a clearance of 0.0357 mm. The schematic
figure of twisted tape insert is given in Fig. 2.
The twisted tapes are manufactured and fixed
