ENHANCEMENT OF HEAT TRANSFER USING
VORTEX FLOW CHANNELS
DIPESH THAPA
Department of mechanical, Koneru Lakshmaiah University, India
Email:dipesh.thapa1995@yahoo.com
ABSTRACT
The prime objective of present work is to study the heat transfer augmentation through various fluid flow channel
geometries both experimentally and using ANSYS WORKBENCK 15.0. In this paper the heat transfer rate between
circular cross section, tapered cross-section (both convergent and divergent) and the vortex flow channel is compared. It
has been found that the heat transfer rate increases significantly in the vortex flow channel in compare to any other flow
channel geometry when all other parameter like fluid, inlet temperature of fluid and atmosphere, surface area, volume of
channel and mass flow rate are kept to be same. The only reason that make difference in heat transfer rate between these
flow channel of the circular and tapered cross- section type and vortex flow channel is the flow pattern, in the circular and
tapered cross- section flow channel fluid flow domain is mostly dominated by the laminar flow whereas in the vortex flow
channel the high Reynolds turbulence flow can be obtain which enhances the heat transfer rate.
Index Terms: Vortex flow channel, Natural Convection, Heat transfer augmentation, low Reynolds turbulent
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INTRODUCTION
Heat transfer Enhancement techniques are commonly
used in areas such as process industries, heating and
cooling in evaporators, thermal power plants, airconditioning equipment, refrigerators, radiators for space
vehicles, automobiles, Electronic devices, Chemical
process etc. Heat transfer rate can drastically change the
performance and efficiency of any kind of system; either
you consider huge automobiles or the small electronic
chips. This is why the demand for the study of heat
transfer is increasing day by day. In this paper we will
see how the heat transfer rate can be enhanced through
the simple modification of flow channels to vortex
channel.
Fig1: vortex flow channel
Vortex channel is the channel in which the low Reynolds
turbulent (or laminar) flow is converted to high
turbulence flow by producing the swirl or vortex flow
pattern. The vortex flow channel geometry is till now
just has been study for the production of gravitation
hydroelectricity but it may have an effective application
where in the cooling of fluid under atmospheric
condition is required in different industries. There may
be some scenarios in different industries where an
amount of certain fluid is to be transferred from hot zone
to cold zone and eventually certain variation of
temperature is desired without supplying any external
work or minimum work(for forced convection). In this
paper we will just discuss about the free convection but
this kind of principle can also be used where the forced
convection is required. Pin-fin heat exchanger mostly
focuses about the production of the vortex by using large
number of extension which may be more costlier more
over the heat transfer takes place in the large span of
region whereas in case of vortex flow channel the heat
transfer is dominated in particular region which means if
we want to implement forced convection we can just
focus for some particular region(i.e core region and swirl
region) hence the size of heater or cooler decreases
significantly which results in both work efficient and
cost efficient.
EQUATIONS AND BOUNDARY
CONDITIONS
The governing equations in this system are the
incompressible Navier-Stokes equation (Eq. 1) and
continuity equation (Eq. 2) accounting for the motion of
the fluid
(
(
Also,
Where
)
Ti is inlet temperature of fluid=323 K ,
) (1)
A is the surface area for convection
This value is chosen as below as the boiling point of
water is 100 °C. At boiling temperature, water will start
changing its phase and bubbles may begin to form which
is undesirable for this study.
(2)
Ta = wall temperature which is assumed to be 300 K
(27 °C).
(3)
The analysis of the flow is performed using ansys
workbench 15.0. Inlet temperature of the fluid is
assumed to be 300K the external environment
temperature is assumed to be 300k. The constant flow of
0.432 kg/s of water were given from inlet. These values
of inflow for the particular geometry and dimension are
taken based upon the experiment performed on 2014-0820 at KL university fluid mechanic lab.
For the ansys analysis part the geometry has been
meshed with higher order triangular elements. Size of
the elements at the inlet and outlet boundaries is chosen
to be finer than those of other boundaries. Three
dimensional meshing was performed. To investigate the
accurate property several trials have been made for
different flow rate.
EQUATIONS FOR
THE
HEAT
COEFFICIENT
And
Where D is the hydraulic diameter
EXPERIMENTAL PROCEDURE
CALCULATING
TRANSFER
Fluid is passed through the inner wall of the flow
channels. The mode of heat transfer is convection and
steady state condition is assumed. So, heat transfer in the
fluid can be expressed as
;Where T0 is outlet average
temperature
The average heat transfer coefficient, h and the mean
Nusselt number, Nu are estimated as follows:
Fig2: Vortex flow channel
Fig3: Circular cross section flow channel
RESULT AND DISCUSSION:
Table for experimental analysis:
For vortex flow channel:
S
N
O.
Raise
in
level
of
tank
(cm)
Ti
me
Ta
ken
for
rais
e
(sec
)
Dischar
ge
Throug
h
the
pipe
(cm3/sec
)
Temperatu
re
at
inlet
( Ti 0C)
Temperatu
re
at
outlet
( Ti 0C)
Temperatu
re
Difference
(Ti-To)
0
C
1
10
19
473.68
50.23
48.26
1.97
10
33
272.72
49.34
47.16
2.18
Fig4: Formation of vortex in vortex flow channel
APPARATUS REQUIRED: Water vortex generator,
Stop watch, Vernier caliper, Discharge tank,
Thermocouples, Water (working fluid)
PROCEDURE: At first fill the discharge tank with to
the certain level, and heat the water using electric heater
till the temperature of the water becomes to 500c, the
temperature of the water in the tank is measured
continuously using the thermocouple. Now open the
outlet of the tank till the water level decrease is 10
centimeter. Measure the time required to decrease the
level of tank by using stop watch. Now without
disturbing the outlet valve connect the flow to the
circular cross section pipe, read the outlet temperature
using thermocouple based sensor. Now again without
disturbing the flow of water connect the flow to vortex
channel and measure the outlet temperature using the
thermocouple.
2
For Circular cross-section flow channel
S
N
O.
Raise
In
level
of
tank
(cm)
Time
taken
for
raise
(sec)
Dischar
ge
Throug
h
the
pipe
(cm3/sec
)
Temperat
ure
at
inlet
( Ti 0C)
Temperat
ure
at
outlet
( Ti 0C)
Temperat
ure
Difference
(Ti-To)
0
C
110
19
473.68
50.21
49.53
0.68
10
33
272.72
49.29
48.37
0.92
OBSERVATION:
1.
2.
3.
4.
Size of the collecting tank: 200cmX30cmX30cm
L.C of stop watch: 1 millisecond
L.C of thermocouple:0.010 C
Volume of fluid flow path for each
geometry:722.083cm3
5. Surface area for convection: 118.22 cm2
1
2
Table for ANSYS analysis:
For divergent flow channel
For vortex flow channel:
SN
NO.
1
Raise in
level of
tank
(cm)
10
Time
Take
n
for
raise
(sec)
19
Discharg
e
through
the pipe
(cm3/sec)
473.68
Tempe
rature
at
inlet
( Ti
0
C)
Temperat
ure
at outlet
50.23
48.09
Temper
ature
SN
N
O.
10
33
272.72
49.34
46.97
Time
Take
n
for
raise
(sec)
Dischar
ge
10
19
10
33
level
of
Differen
ce
(TiTo)
0
C
2.14
tank
(cm)
1
2
Rais
e
In
2.37
Temperat
ure
at
inlet
( Ti 0C)
Temperat
ure
at
outlet
(To0C)
Temperat
ure
Difference
(Ti-To)
0
C
473.68
50.21
49.33
0.88
272.72
49.29
48.24
1.05
through
the
pipe
(cm3/sec
)
2
For Circular cross-section flow channel
SN
NO.
Rais
e
In
Tim
e
take
n
for
rais
e
(sec)
Dischar
ge
through
the
pipe
(cm3/sec
)
Temperat
ure
at
inlet
(
Ti
0
C)
Temperat
ure
at
outlet
( Ti
0
C)
Temperat
ure
Difference
(Ti-To)
0
C
1 10
19
473.68
50.21
49.39
0.82
10
33
272.72
49.29
48.26
1.03
leve
l
of
tan
k
(cm
)
2
For convergent flow channel:
SN
NO.
2
Rai
se
in
leve
l of
tan
k
(cm
)
Tim
e
Take
n
for
raise
(sec)
Dischar
ge
through
the pipe
(cm3/se
c)
Temperat
ure
at
inlet
( Ti 0C)
Temperat
ure
at
outlet
( Ti 0C)
Temperat
ure
difference
(Ti-To)
0
C
1 10
19
473.68
50.23
49.49
0.74
10
33
272.72
49.34
48.4
0.94
Form the above tables the temperature difference of
water for inlet and outlet is of 1.97for 0.473lit/sec and
2.180C for 0.273lit/sec of flow rate whereas for the same
flow rate the circular cross-section flow channel is just
0.680c and 0.92 respectively. Hence, it is very clear that
the temperature difference we got from the vortex flow
channel is more than twice as much as the circular crosssection channel for 500c of water and 27 0C atmospheric
temperatures. Similarly, the temperature difference we
have got experimentally for 0.473lit/sec is 2.140C and
2.370c for vortex flow channel and circular cross-section
flow channel and 0.82 and 1.03 for 0.273lit/sec, which
implies that the heat transfer rate through this channel is
also inversely proportional to the mass flow rate. So the
heat transfer rate for the vortex channel was significantly
high for vortex flow channel in compare to the circular
cross-section flow channels. Here for the experiment the
only things made different between those to flow
channels was their geometry keeping all other boundary
condition same for both. That means only the reason to
have the heat transfer rate enhanced in the vortex flow
channel is because of the flow pattern of the fluid.
CONCLUSIONS
This study is an attempt to present the effect of different
geometries of flow channel on heat transfer
characteristics under steady state flow condition. The
study has shown that the vortex flow channel have
significant heat transfer in compare with different
common flow geometry like circular cross-section flow
channel, convergent flow channel and divergent flow
channel for same volume and same surface area exposed
to surrounding. Actually for the heat transfer through the
flow channel this geometry (i.e. vortex flow channel) has
never been used for any of the industries that means the
study of these kinds of geometries are not done in the
way they need to be. The efficiency of any industries not
only depends upon the huge losses which can be sensed
directly, but there also may be some minor losses which
instead of getting the solution we might have ignored.
The significant of these vortex flow channel does not
only limits at a good heat exchanger but also have many
significance like production of hydroelectricity, aeration
of chemicals etc. The result in the above study have
already shown that the vortex flow channels enhances
the heat transfer rates and more than that significant heat
transfer only takes place in a small confined area that
means if we require the force convection instead of
focusing whole flow domain we can just have our focus
in this domain, which reduces the requirement huge size
and capacity of forcing device which I think is most
important aspect of my study. .
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GRAPHS AND PLOTE FOR 0.272lit/sec FLOW FOR DIFFERENT FLOW CHANNELS:
Fig4: For vortex flow channel
Fig5: For circular cross-section flow channel
Fig6: For convergent flow channel
Fig7: For divergent flow channel
GRAPHS AND PLOTE FOR 0.272lit/sec FLOW FOR DIFFERENT FLOW CHANNELS:
Fig8: For vortex flow channel
Fig9: For circular cross-section
Fig10: For convergent flow channel
Fig11: For divergent flow channel