The convective heat transfer through circular depends on the inclination of pipe,Dia of pipe,heat value and insulation provided.

1. UNDER THE GUIDENCE OF
Prof. BASAVARAJ H TALIKOTI
Mechanical dept.
SPCE Bengaluru
SHRI PILLAPPA COLLEGE OF ENGINEERING

2. OVERVIEWOVERVIEW
 Abstract
 Introduction
 Literature Survey
 Layout of experimental set up
 Specifications
 Experimental Work
 Methodology
 Operating procedure
 Sample Reading
 Results And Discussion
 Graphs
 Conclusions
 Scope for future Work
 References

3. ABSTRACTABSTRACT
 In the present work the experimental setup for
convective heat transfer coefficient of air flowing
through a copper tube of circular cross section is
fabricated. This setup can be used to find out heat
transfer coefficient at different operating conditions.
 Using the experimental setup, convective heat transfer
coefficient of air passing through circular duct was
determined under the following conditions.
o By varying heat input.
o By varying blower valve position.
o By varying inclination of circular duct.

4. INTRODUCTIONINTRODUCTION
Heat transfer is defined as “transmission of energy from
one region to another as a result of temperature gradient”.

5. LITERATURE SURVEYLITERATURE SURVEY
 Hilpert was one of the earliest researchers in the area of forced
convection from heated pipe surfaces. He developed the correlation
Nu= hd/K) =C Re
m
Pr0.333.
 Fand and Keswani reviewed the work of Hilpert and recalculated
the values of the constants C and m in the above equation using
more accurate values for the thermo physical properties of air.
 Zukaukasz Another correlation proposed by Zukaukas for
convective heat transfer over a heated pipe is given by
Nuf =c Ref Prf
0.37
( Prf/ Prw)0.25
 Churchill and Bernstein Churchill and Bernstein proposed a
single comprehensive equation[5] that covered the entire range of
ReD for which data was available, as well as a wide range of Pr.
The equation was recommended for all ReD.Pr > 0.2 and has the
form
NuD= 0.3+ *[1+(ReD/282,000)5/8
]4/5
This correlation was based on semi-empirical work and all
properties were evaluated at the film temperature.

6. Contd…..Contd…..
 Dittus Boelter relation
The conventional expression for calculating the heat transfer
coefficient in fully developed turbulent flow in smooth pipes is the
Dittus Boelter equation
Nu = C Rem Prn
 where C, m and n are constant determined experimentally. these
values - C=0.023, m=0.8 and
 n = 0.4 for heating of the fluid
 n = 0.3 for cooling of the fluid
 Properties of this relation have been calculated at the average fluid
bulk temperatures. Equation is valid for single phase heat transfer
in fully developed turbulent flows in smooth pipes for fluids with
Prandtl number ranging from 0.6 to 100 at low heat fluxes. At high
fluxes the fluid properties changes resulting in higher errors.

7. LAYOUT OF EXPERIMENTALLAYOUT OF EXPERIMENTAL
SET UPSET UP
Where T1
= inlet temperature of air
T6
= outlet temperature of air
T ,T ,T ,T = Specimen surface temperature

8. SPECIFICATIONSSPECIFICATIONS
 Specimen : Copper circular Tube.
 Size of the Specimen : 33 mm x 33 mm x 500 mm long.
 Heater : Externally heated, Nichrome wire
Band Heater 500W.
 Ammeter : Digital type,0-20amps, AC.
 Voltmeter : Digital type, 0-300volts, AC.
 Dimmer stat for heating Coil : 0-230v, 2amps.
 Thermocouple Used : 6 no. k-type, range: 0 to 4000
c.
 Centrifugal Blower : Single Phase 230v, 50 Hz,
13000rpm.
 G. I pipe diameter : 33 mm.
 Outer duct : Aluminum

9. EXPERIMENTAL WORKEXPERIMENTAL WORK
Fig. 1Test section copper circular duct with
insulation and heater at 0º.º.
.
Fig 2: Experimental Setup of circular duct with
Insulation and Heater at 30º.
Fig 3: Experimental Set up of circular duct
with Insulation and Heater at 60º.
Fig 4: Experimental Setup of circular duct with
Insulation and Heater at 90º.

10. Contd….Contd….
Fig 5:Experimental Setup of Circular Cross
Section Duct at 1200
Fig 6:Experimental Setup of Circular Cross
Section Duct at 1500
 The above figure shows an experimental setup which comprises
of test specimen made up of copper having circular cross section
having dimensions 33x33x500mm, which is connected to a blower
through a GI pipe and bellows.
 The equipment is mounted on a 2ftX3ft rectangular table which
is made up of mild steel sheets and plane woods.

11. Contd….Contd….
 Angle of inclination can be varied in terms of 300,
600
,
90°,120° and 150° with the help of lever and nut-bolt
arrangement.
 Here five thermocouples of k-type, two for inlet and
outlet i.e. T4 and T5, rest of the three (i.e. T1,T2 andT3)
thermocouples are placed at equal distance on the
surface of test specimen.
 With the help of blower regulator, velocity of air can be
set.
 Heat input can be set with the help of variac provided on
control panel and same can be read out digitally with the
help of voltmeter and ammeter.
 Manometer is provided on the board to indicate the
level and hence velocity for different valve opening can

12. METHODOLOGYMETHODOLOGY
 The apparatus consists of a blower for forced
circulation.
 The air from the blower passes through a flow passage
at different valve positions, heater and then to the test
section.
 A heater placed around the tube heats the air, heat input
is controlled by a dimmer stat. Heat input is measured
with the help of voltmeter and ammeter.
 Temperature of the air at inlet and at outlet are measured
using thermocouples. The surface temperature of the
tube is measured at different sections using
thermocouples embedded on the circular duct.
 Test section is enclosed with wool and rope, where the
circulation of rope avoids the heat loss to outside.
 The entire test rig is mounted on a table as shown

13. OPERATING PROCEDUREOPERATING PROCEDURE
 Plug the 230 Volts AC mains to the main supply line and switch
ON mains.
 Put on the heater and adjust the voltage to a desired value by using
electronic voltage regulator and maintain it as constant
 Switch ON the Blower and regulate the flow for desired value by
using electronic regulator (First press the switch on the blower and
then control through the electronic regulator)
 Allow the system to stabilize (reach steady state).This may take
about 10-15 minutes.
 Note down all the temperatures T1 to T5, voltmeter, ammeter
readings and manometer readings.
 Repeat the experiment for different heat input and air flow rates.

14. SAMPLE READINGSSAMPLE READINGS
Readings for the velocity of 11.097 m/s and 40v heat input at 00
Procedure for calculation
Sl
No.
Manometer
reading in
cm
V
volts
I amps T1
0
c T2
0
c T3
0
c T4
0
c T5
0
c
h1 h2 hw
01 0.7 0 0.7 40 0.61 40.6 42.7 40.3 40.6 40
Contd….
 Note down all the parameters which are displayed on control
panel,which includes voltage, current & all temperatures.
 Calculate the surface temperature and ambient temperatures by
using the following formulae :
surface temp = (T1+T2+T3)/3
Ta= (T6+T5)/2
Tfilm =( Ts+Ta)/2
 Find the properties of air at film temperature like kinematic viscosity (ν),
prandtl number (Pr), thermal conductivity (K) from heat transfer data
hand book.

15.  Calculate the Reynolds number (Re), with the formula Re =
ρvD/μ
 Based on the Reynolds number, select the Hilpert’s constants like
C and m.
 Calculate Nusselt number using parameters Pr,C,m,ReD and the
formula is
Nu = C Rem
x
pr0.333
.
 Calculate the convective heat transfer coefficient by using the
formula.
h=( KxNu)/ D
Contd….
 Repeat the calculation part for following different situations.
 By keeping the valve openening and varying the heat input in
terms of 40,60,80,100,120 and 140 m/sec ,for various angle of
inclinations like 00
,300
,600
,900
,120° and 150°.
 And also varying the blower valve positions by 1/4th
,1/2,3/4th
and
full open, for various angle of inclinations like
00
,300
,600
,900
,120° and 150°.
 Tabulate all the calculations for separate angle of inclinations.

16. RESULTS AND DISCUSSIONRESULTS AND DISCUSSION

17. SL NO.
Inclination Valve
position
Velocity
(m/s)
Heat input
(W) Re Nu
H
(kW/m2 0
k)
01 00
1/4th
11.097 140.3 21369 81.02 64.98
1/2 12.578 140.3 25132.5 89.6 70.911
3/4th
12.58 140.3 24736.01 88.768 70.038
Full 11.094 140.3 22266.085 83.1905 65.237
02 300
1/4th
8.386 140.3 16052.12 68.052 54.533
1/2 12.58 140.3 24729.285 88.73 70.243
3/4th
12.58 140.3 24926.84 89.183 70.397
Full 11.86 140.3 23680.18 86.397 67.967
03 600
1/4th 9.375 140.3 17835.88 72.45 58.314
1/2 16.245 140.3 31869.22 103.637 81.99
3/4th
16.245 140.3 32268.645 104.615 82.49
Full 16.245 140.3 32191.638 104.498 82.45

18. SL NO. Inclination Valve
position
Velocity
(m/s)
Heat input
(W) Re Nu
h
(kW/m2 0
k)
04 900
1/4th 9.375 140.3 18026.91 72.92 120.86
1/2 20.54 140.3 40866.74 120.86 95.382
3/4th
22.966 140.3 46128.92 130.99 102.74
Full 23.72 140.3 47907.577 135.04 105.64
05 1200
1/4th
13.26 140.3 25766.61 90.988 72.51
1/2 21.787 140.3 43276.04 124.92 98.48
3/4th
23.345 140.3 46297.83 131.1 103.56
Full 23.34 140.3 46990.67 132.915 104.26
06 1500
1/4th
12.57 140.3 21042.95 81.36 70.12
1/2 19.66 140.3 39401.96 117.44 92.255
3/4th 24.08 140.3 48753.44 136.91 108.44
Full 23.34 140.3 46549.82 130.92 103.88

19. Variation of heat transfer coefficient withVariation of heat transfer coefficient with
inclination for different velocitiesinclination for different velocities
 As it seen from the above graph velocity of air flow influences the
heat transfer coefficient at a greater extent than the inclination.
GRAPHS

20. Variation of Reynolds number andVariation of Reynolds number and
Nusselts number at all inclinationsNusselts number at all inclinations
 From the above graph it is clear that, irrespective of angle of inclination
of duct, there is a direct proportionality between the Reynolds number
(Re) and Nusselts (Nu) number. i.e., by increasing the velocity of air there
must be an increase in the Reynolds number and Nusselts number, thus
increasing the heat transfer coefficient.

21. CONCLUSIONSCONCLUSIONS
 During the test it was found that convective heat transfer
coefficient increases in air stream velocity at constant heat input
and inclination.
 From the result it is evident that heat transfer coefficient is
maximum for a constant heat input of undergoes and 9.375 m/sec
velocity when the when the duct was inclined at 900
inclination.
 The minimum heat transfer coefficient was observed for heat input
of 292.6watts and air stream velocity of 8.386 m/sec with 300
inclinations.
 The decrease in heat transfer coefficient may be due to restriction
in the flow of air when the duct is above 900
.

22. SCOPE FOR FUTURE WORKSCOPE FOR FUTURE WORK
 The experimentation can be carried out for different fluids.
 The determination of variation of heat transfer coefficient for
varying cross section of the copper duct.
 The test rig can be computerized to obtain more accurate results.
 Fins can be attached on the specimen and the effect of fins on heat
transfer coefficient can be studied.

23. ReferencesReferences
 Krishpersad Manohar, Kimberly Ramroop. “A Comparison of Correlations for
Heat Transfer from Inclined Pipes” Volume 4, Issue 4, October 2010.
 2. Hilpert, R. “Heat Transfer from Cylinders,” Forsch. Geb. Ingenieurwes, 4:215,
1933.
 3. Fand, R. M. and K. K. Keswani. “A Continuous Correlation Equation for Heat
Transfer from
 Cylinders to Air in Crossflow for Reynold’s Numbers from 10-2 to 2(10)5,”
International Journal of Heat and Mass Transfer, 15:559-562, 1972.
 4.Zukauskas, A. “Heat Transfer From Tubes in Crossflow,” Advances in Heat
Transfer, 8:87-159, 1987.
 5. Churchill, S. W. and M. Bernstein. “A correlating Equation for Forced Convection
from Gases and Liquids to a Circular Cylinder in Crossflow,” J. Heat Transfer,
99:300-306, 1977.
 Sunil S and Basavaraj H Talikoti, “Fabrication Of Experimental Setup To Evaluate
The Convective Heat Transfer Coefficient Of Air Flowing Through An Inclined
Circular Cross Section Duct”. ISSN: 2278-0181 www.ijert.org IJERTV4IS020027
Vol. 4 Issue 02, February-2015.

24. THANK YOU