Declaration of Authorship We hereby certify that this thesis is our own work and was completed for partial fulfilment of the undergraduate degree in Mechanical Engineering at Bangladesh University of Engineering and

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Declaration of Authorship
We hereby certify that this thesis is our own work and was completed for partial fulfilment of the
undergraduate degree in Mechanical Engineering at Bangladesh University of Engineering and
Technology. We declare that where any or all part of this thesis has previously been submitted
for a degree or any other qualification at this university or any other university, this has been
clearly stated. All the published work of others and all sources of information have been properly
attributed and acknowledged and with the exception of such references, this work is entirely our
own and all authors have contributed equally to the project.
Signed:
Md Imran Khan
Md. Mamun Billah
Mohammed Mizanur Rahman
Abstract
This thesis illustrates a numerical study of steady two dimensional mixed convention heat
transfer phenomena in a rectangular channel with an active flow modification system by means
of a variable speed heat conducting cylinder that is placed at the center of the channel. In the
current study, an isothermal low temperature is maintained on the upper wall while a discrete
isoflux heater is installed on the lower wall. The Prandtl number of air flowing through the
channel is kept fixed at 0.71 while the Reynolds and the Grashof numbers are varied
considerably for four different configurations of the cylinder such as: i) channel with no cylinder,
ii) channel with stationary cylinder, iii) channel with cylinder rotating clockwise and iv) channel
with counter clockwise rotating cylinder. The speed ratio is varied as 0.5, 1.0 and 1.5 for only the
counter-clockwise and clockwise rotational setups. The impact on the flow pattern and
temperature field is evaluated in terms of the distribution of streamlines, isothermal lines while
the impact on the heat transfer phenomena is analyzed in terms of the local and surface averaged
Nusselt numbers. The results point out that the cylinder’s configuration, rotational speed,
Grashof and Reynolds numbers significantly impact the flow pattern, temperature field and the
heat transfer characteristics. Glapke and Afsaw [11] analyzed natural convection in a circular
enclosure with a concentric hexagonal cylinder.
Acknowledgements
All praises be to Allah, the Most Gracious and Most Merciful, for giving us the strength and
knowledge to successfully complete this thesis.
We are extremely grateful and honored to have had the opportunity to work under the
supervision of Dr. Mohammad Nasim Hasan, Associate Professor of Department of Mechanical
Engineering, Bangladesh University of Engineering and Technology whose kindness, patience
and guidance helped us shape our work into what it is today. For his mentorship and for the time
and effort that was put in to make us understand the problem more clearly, we would like to
express our sincerest gratitude and appreciation.
Dedicated to our beloved parents
Table of Contents Page
Declaration of Authorship 1
Abstract 2
Acknowledgements 3
Dedication 4
List of Figures 7
List of Tables 8
Nomenclature 9
Chapter 1 11
1.1 Convection Heat Transfer 11
1.1.1 Natural Convection 13
1.1.2 Forced Convection 14
1.1.3 Mixed Convection 14
1.2 Classification of Mixed Convection 15
1.3 Mixed Convection in Cavity 16
1.3.1 Closed Cavity Problems 16
1.3.2 Open Cavity Problems 17
1.4 Literature 17
Chapter 2 Mathematical Modelling 19
2.1 Physical Model 19
2.2 Assumptions 20
2.3 Governing Equations 20
2.4 Dimensional Analysis 21
2.4.1 Dimensionless Numbers 21
2.5 Dimensionless Boundary Conditions 22
Chapter 3 Numerical Methodology 24
3.1 Advantages of Numerical Analysis 24
3.2 Solution of Differential Equations 25
3.3 Finite Element Method 26
3.3.1 Advantages and Disadvantage of the Finite Element Method 30
3.4 Galerkin Weighted Residual Method 31
3.5 Mesh Generation 33
3.6 Grid Sensitivity Test 35
3.7 Validation of Isothermal Lines and Streamlines 36
3.8 Summary 38
Chapter 4 Results and Discussions 39
4.1 Effect of Grashof Number and Reynolds Number 40
4.2 Effect of Cylinder Speed Ratio 49
4.3 Effect on Heat Transfer Characteristics 58
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DeclarationofAuthorshipWeherebycertifythatthisthesisisourownworkandwascompletedforpartialfulfilmentoftheundergraduatedegreeinMechanicalEngineeringatBangladeshUniversityofEngineeringandTechnology.Wedeclarethatwhereanyorallpartofthisthesishaspreviouslybeensubmittedforadegreeoranyotherqualificationatth...

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