• Tiada Hasil Ditemukan



Academic year: 2022


Tunjuk Lagi ( halaman)







A thesis submitted in fulfillment of the requirement for the degree of Doctor of Philosophy ( Engineering )

Kulliyyah of Engineering

International Islamic University Malaysia





Thermal management for heat generation in the power electronics, concentrated solar panels and fuel cells requires a special and effective cooling system. A series of numerical runs for parametric study, such as the effect of fins space, heights of fins, effect of embossed impressions, the shape of embossed impressions and the angle of attack of the embossed impressions have been carried out. Firstly, six geometries, have 0.2 mm, 0.5mm 1mm fins space and with 3 and 5 mm heights compared to smooth heat sink were studied. Secondly three different geometries heat sinks with fin spacing’s of 0.2 mm, 1.0 mm and Embossed fins along were studied numerically to investigate the effect of embossed impressions. Thirdly three different geometries heat sink with triangular, rectangular and semicircle embossed impressions attached to the fins were studied numerically to investigate the effect of embossed shape. Finally, the embossed impressions angles 30, 45, 60 and 90 degree were investigated. Source load 325 W at the bottom of heat sink and different volumetric flow rate 0.5, 0.75 and 1 liter per minute were used. The results have shown that, the fined heat sink has more heat transfer rate, 194.3 watts at 1liter per minute. Moreover, thermal resistance and base temperature reduced 58 % and 30.7 % compared to flat plate respectively. Also, the height of fins reduced the base temperature 2.84℃. Likewise, the embossed impressions heat sink reduced the base temperature about 5.8% lower than the best reported base temperature using a water compared with commercial heat sink in the open literature. In addition to, for spacing 0.2 mm heat sink, the highest thermal resistance was 0.0578 K/W that was decreased to as little as 0.0292 K/W by using an embossed heat sink. The triangular embossed impression has attained the lowest heat sink base about 6.45% lower than the best reported base temperature in the open literature. The thermal resistance was 0.028, 0.030 K/W and 0.025 of rectangular, semicircle and triangular embossed shapes respectively at mass flow rate 1LPM. Angle of attack 45 degree was the best compared as, the lowest heat sink base temperature of 37.2 C was achieved by using a triangular embossed heat sink at angle 45 which was about 3.5 C lower than the best reported base temperature of 40.7 C. The average heat transfer coefficient was attained to be 3239 W/m2 K, 2828 and 3474 W/m2 K for the case of rectangular, semicircle and triangular embossed shapes, respectively. Finally, two embossed and smooth heat sinks were fabricated at IIUM laboratory, then tested experimentally under forced convection using water, Reynolds 800-2800.This work suggests that one can adapt larger number of embossed channel and smaller fins space to have less thermal resistance rather than only increasing the pumping power.



ةصلاخ ثحبلا

Abstract in Arabic

للأاو ، تاينوتركللاا في ةدلوتلما ةرارحلل ةيرارلحا ةرادلإا نا طتت دوقولا ايلاخو ةزكرلما ةيسمشلا حاو

دوجو بل

.لاعفو صاخ ديبرت ماظن افترا ،فناعزلا ينب ةفاسلما يرثأت لثم ،ةيترمارابلا ةيددعلا تاساردلا نم ةلسلس

ع ةيوازو تاعابطنلاا لكش ثم ،)ةشوقنلما تاعابطنلاا( فناعزلا يلع ةقصللما ماسجلاا يرثأت ،فناعزلا لاب عينصت تم .موجلها تلل ايبيرتج تاعولابلا رابتخا ثم ،ةفرخز نود ةرارح ةعولابو ةفرخزلما ةرارلحا ةعو

في قيقح

ةنراقلماو يرارلحا ءادلأا .

، فناعزلا ينب تافاسم ةعبرأ ةسارد تم 2.0

،مم 2.0 و 1 ينعافترا ا مم

3 2.0 ةف لتخت يمج لحا قفدت لدعمو ةرارلحا ةعولاب نم يلفسلا ءزلجا في طاو 300 ليمتح ردصم .مم 0 و ، 0 عافترلال C 71.. و 3..3 ةدعاق ةرارح ةجرد نىدأ تناكو . ةدحاولا ةقيقدلا في ترل 1 و 2..0

مم 3 و

،ةرارلحا لقن لدعم نم ديزلما اهيدل ةعولاب يرارلحا نسحتلا نأ جئاتنلا ترهظأ دقو ،لياوتلا ىلع مم 1.7.3 في طاو

1 ةقيقدلا في ترل .

فنخا ،كلذ ىلع ةولاعو ةرارلحا ةجرد ةدعاقو ةيرارلحا ةمواقلما تض


٪ و 32..

٪ تضفخ فناعزلا عافترا نإف ،كلذ ىلع ةولاعو .لياوتلا ىلع ةحطسم ةحول عم ةنراقم

ةيساسلأا ةرارلحا ةجرد 0.37

نم ةفنعز دعابت عم ةفلتخت ةيسدنه ضاوحأ ةثلاث ةسارد تم . ℃ 2.0

،مم رارح ةجرد نىدأ قيقتح تم .ةفرخزلما تاعابطنلاا يرثأت في قيقحتلل ايددع ع ةشوقنم فناعزو مم 1.2 ة ٪ 0.3 وحنب لقأ ناك يذلا ةفرخزلما ةرارلحا ةعولاب مادختساب ج 33.0 ةرارلحا ةعولاب ةدعاق لضفأ نم

ةقباسلا تاساردلا في تركذ ةدعاق ةرارح ةجرد 72..

C ةرارلحا ةجرد تضفنخا . ءالما مادختساب

لحا ةمواقلماو ةيساسلأا )ةعرسلا( زدلونير ددع ةدايزو ةفرخزلما تاعابطنلاا مادختساب ةيرارلحا فراصملل ةيرار

ةرارلحا ةدعابلم ةبسنلاب امأ .ةرارلحا ةعولاب للاخ نم لئاسلا 2.0

ةيرارح ةمواقم ىلعأ تناك دقف ،مم


نم لقأ لىإ اهضيفتخ تم تيلاو طاو / طاو وليك 2.20.0

ادختساب ةعاس / طاو وليك ةعولاب م

طسوتم غلب دقو .ةفرخزلما ةرارلحا لماعم

لاقتنا ةرارلحا 1070..10 طاو

/ ترم عبرم و 0....020

W / m2 K دعابتلا ةلالح

2.0 ةرارحلل ةفلتخت طانما ةثلاث ةسارد تم .لياوتلا ىلع ةفرخزم فناعزو مم

لا ىلع ةقصلم ةيرئاد فصن و ةليطتسم ، ةثلثم تاعابطنا عم ةيسدنلها قحتلل ايددع فناعز

يرثأت في قي

ةعولابلا ةدعاق في ةرارح ةجرد نىدأ قيقتح تم .شوقنلما لكشلا 3..0

ةشوقنلما ةرارلحا ةعولاب مادختساب ج

وحنب لقأ تناك تيلاو ةثلثلما ..70

٪ ةقباسلا تاساردلا في تركذ ةدعاق ةرارح ةجرد لضفأ نم

72.. اقلماو ةيساسلأا ةرارلحا ةجرد تضفنخاو C .

تاعابطنلاا حئافص مادختساب ةرارلحا فراصلما نم ةيرارلحا ةمو

ينب ةيرارلحا ةمواقلما ناكو .ةرارلحا صاصتما قيرط نع لئاوسلل )ةعرسلا( زدلونير ددع ةدايزو 2.203

، LPM. 1 يعاملجا قفدتلا لدعم في لياوتلا ىلع يثلاثلاو ،ةليطتسلما 2.200 و /W ك 2.232 ناكو

ارلحا لقن لماعم غلب ب طسوتم ةر

32.7 W/m2 K, 03.3

W/m2 K و

37.2 W/m2

K تاعابطنلاا اياوز تناك .عابطنلاا ةيواز يرثأت ةساردل .لياوتلا ىلع ، ةثلثلما او ةيرئادلاو ةليطتسم ةلالح

32 ، 70 ، .2 و .2 زدلونير ددع في يرسقلا يرارلحا لملحا تتح ةجرد 1.02

ةجرد نىدأ ققتح .

ةعولاب ةدعاق ةرارح ا

3..0 ةيوازب يثلاث فرخزم ةرارلحا ةعولاب مادختساب ج 70

لياوح ناك يذلا

3.0 72.. ةقباسلا تاساردلا في ةرارح ةجرد ةدعاق لضفأ نم لقأ ج ةمواقلماو ةيساسلأا ةرارلحا ةجرد .

اقلما تناك ىلعأو نىدأ . تاعابطنلال ةفلتخت اياوز مادختساب تضفنخا ةرارلحا فراصلما نم ةيرارلحا و




ةيرارلحا 2.200 و

2.272 ةيوازب ةيثلاثلا لاكشلأل

70 ةيواز في ةيرئادلا ، 32

ةرارلحا لقن لماعم .

لىإ تغلب طسوتم 303.

K W/m2 ،

0303 و 37.7 K W/m2 ةيرئادلاو ةليطتسلما لكشلال

او فناعزلا ةفرخزم اهمدحا ينتيرارح ينتعولاب رابتخا تم ،ايرخأ.لياوتلا ىلع ،ةيثلاثلا و خ

فناعزلا اسلم ىر

زدلونير ددع ،يرارح لقانك هايلما مادختساب يرسقلا يرارلحا لملحا تتح ايبيرتج 322

- 0322 ةدحاو .

نم ًلادب ةيرارح ةمواقم لقأ نوكي ةحاسم رغصأو ةفرخزم فناعز تاذ ةانق نم بركأ ددع فييكت نكيم

طقف خضلا ةقاط ةدايز





The thesis of Suliman M. M. Suliman has been approved by the following:


Waleed Fekry Faris Supervisor


Ahmad Faris Ismail Co-Supervisor


Waqar Asrar Internal Examiner


Ahmad Kamal Ariffin External Examiner



Rosli bn Abu bakar External Examiner


Akram M Z M Khedher Chairman




I hereby declare that this thesis is the result of my own investigation, except where otherwise stated. I also declare that it has not previously or concurrently submitted as a whole for any other degree at IIUM or other institutions.

Suliman M. M. Suliman

Signature………. Date: ………






I declare that the copyright holders of this thesis are jointly owned by the student and IIUM

Copyright © 2018 Suliman M. M Suliman and International Islamic University Malaysia.

All rights reserved.

No parts of this unpublished research may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior written permission of the copyright holder except as provided below.

1. Any material contained in or derived from this unpublished research may be used by others in their writing with due acknowledgement.

2. IIUM or its library will have the right to make and transmit copies (print or electronic) for institutional and academic purposes.

3. The IIUM library will have the right to make, store in a retrieval system and supply copies of this unpublished research if requested by other universities and research libraries.

By signing this form, I acknowledged that I have read and understand the IIUM Intellectual Property Right and Commercialization policy.

Affirmed by Suliman M. M Suliman

….………..….. ………..……….…..

Signature Date




First of all, thanks is due to Allah, the Most Gracious, Most Merciful (S.W.T.) whom we attain our ability and strength. I would like to express my gratitude and appreciation to my supervisor Prof. Dr. Waleed Fekry Faris for his wise supervision, advice, guidance, suggestion, and support during the research time.

I would like to express my gratitude and appreciation to my Co-supervisor Prof.

Dr. Ahmad Faris Ismail for his wise supervision, advice, guidance, suggestion, and support during the research time.

I would like also to thank the management of CIM and tool laboratory at engineering department for the massive support and assistance.

Thanks are also to my parents and my beloved wife who deserve my deepest appreciation for their un-bordered help and patronize. Special gratitude and appreciation to my beloved baby girl Ikhlas for her sacrifices and being distant from here father. I am grateful for the countless sacrifices they made to ensure that I can pursue and finish my study successfully. Final thank to all my friends who support me particularly Mohamed Aldheeb, Ahmad Adam, Mohame alfatih and Afzal Haq. May ALLAH bless and protect all of them and may they live long and healthy.




Abstract ... ii

Abstract in Arabic ... iii

Approval Page ... v

Declaration ... vi

Copyright Page ... vii

Acknowledgment ... viii

List of Tables ... xii

List of Figures ... xiii

List of Symbols ... xix

List of Abbreviation ... xx


1.1 Research Background ... 1

1.2 Problem Statement ... 3

1.3 Research Objectives ... 3

1.4 Research Methodology ... 4

1.4.1 The Numerical Study ... 5

1.4.2 The Experimental Study ... 6

1.4.3 Measured Variables ... 7

1.5 Thesis Scope ... 8

1.6 Thesis Organization ... 8


2.1 Introduction ... 11

2.2 Shape of Heat Sink Channel ... 13

2.3 Location of Inlet- Outlet of Heat Sink ... 18

2.3.1 Pin Fin Tube Heat Sink ... 20

2.3.2 Porous Media ... 20

2.3.3 Plate fin tube ... 21

2.4 Substrate Size (Macro, Mini, Micro) ... 23

2.4.1 Macro Size Heat Sink ... 23

2.4.2 Mini Size Het Sink ... 24

2.4.3 Micro Size Heat Sink ... 25

2.5 The Substrate Material ... 28

2.5.1 Silicon Substrate ... 28

2.5.2 Copper Substrate... 29

2.5.3 Aluminum Substrate ... 30

2.5.4 Alloy (composite) ... 30

2.6 Turbulators with Heat Sink ... 30

2.7 Summary ... 36


3.1 Introduction ... 37

3.2 Numerical Computation ... 37



3.2.1 Geometry ... 37

3.2.2 Star-ccm+... 39

3.2.3 Governing Equations ... 40 Conservation of Mass ... 41 Conservation of Momentum ... 42 Conservation of Energy ... 42 Heat Sink Governing Equations ... 42

3.2.4 Physics Setting up and Boundary Condition ... 44

3.2.5 Physics and Boundary Setting ... 45

3.2.6 Meshing ... 45

3.2.7 Meshing Study ... 46

3.2.8 Convergent Criteria ... 46

3.2.9 Validation of Experimental Setup ... 49

3.3 Experimental Setting Up and Fabrication ... 49

3.3.1 Introduction ... 49

3.3.2 Flowchart of the Experiment ... 50

3.3.3 Burr Formulation and Surface Roughness Measurements ... 52

3.3.4 Mini-Tool and Mini-Channel of Substrate Material... 52

3.3.5 Geometric Parameters of the Manufactured Embossed MCHS ... 52

3.3.6 Mini-Channel Fabrication... 54 Workpiece: Stainless Steel ... 54 Electrode: Copper ... 55 Dielectric Fluid ... 56 Smooth Mini-channel Heat Sink and Electrode Preparation ... 56 Machine Setup ... 56

3.3.7 Experimental Set-up for Test Base and Cooling System ... 56 Test Base Block ... 57 Fluid Driving System ... 60 Calibration of the Experimental System ... 62 Experimental Procedure ... 62 Data Reduction ... 63

3.3.8 Uncertainties and Error Analysis ... 63

3.4 Summary ... 65


4.1 Introduction ... 66

4.2 Forced Convection (Parametric Study) ... 67

4.2.1 The Effects of Fins Spacing ... 67

4.2.2 Meshing Study ... 67

4.2.3 Geometry and Physics Model ... 69

4.2.4 Results and Discussion ... 71 The Effect of Fins Spacing ... 71 Temperature Drop and Base Semperature ... 72 Heat Transfer Rate, Thermal Resistance of Heat Sinks and Overall Heat Transfer Coefficient ... 73 The Effect of Fin Height ... 76


xi Heat Transfer, Heat Transfer Coefficient and

Thermal Resistance ... 76 Temperature and Velocity Countors ... 78

4.2.5 Effect of Embossed Impressions Compared with Fin Spacing ... 82 Computational Modeling of the Heat Sink ... 83 Confirmation of Mini-Channel Heat Sink ... 85 Results and Discussions ... 86 Heat Transfer rate and MCHS Geometry ... 86 Heat Sink Geometry and Thermal Resistance .... 89

4.2.6 Effects of Embossed Impressions Shapes ... 92 Geometry and Physics ... 93 Results and Discussion ... 95 Base Temperature and Heat Removed ... 95 Overall Heat Transfer Coefficient and Thermal Resistance ... 97

4.2.7 Embossed Impressions Angles ... 98 Geometry and Physics ... 99 Meshing and Convergence Criteria... 100 Results and Discussion ... 102 Base Temperature and Heat Removed by the Circulating Water ... 102 Overall Heat Transfer Coefficient and Thermal Resistance ... 104 Temperature and Streamline Countors ... 105

4.3 Experimental and CFD Validation ... 109

4.3.1 Results and Discussion ... 109 Temperature Distribution on Surface of Heat Sink ... 109 Base, Outlet Temperatures and Temperature Drop ... 112 Embossed Impressions and Heat Transfer Rate ... 115 Embossed Impressions and Overall Heat Transfer Coefficient ... 116 Thermal Resistance of Heat Sinks and Overall Heat Transfer Coefficient ... 117 Embossed Impressions Effect on Pressure Drop and Power Consumption ... 118

4.4 Summary ... 119


5.1 Conclusion ... 120

5.2 Main Contribution ... 121

5.3 Future Work ... 122


APPENDIX ... 135




Table 3.1 Dimension of Min-Channel Heat Sinks (mm) 44 Table 3.2 Geometric Parameters of the Manufactured Smooth and

EmbossedMCHS Dimension of أeat ٍinks (mm). ... 54

Table 4.1 Active Area (mm2) 86

Table4.2 Ompares Effective Area, Base Temperature, Overall Heat

Transfer Coefficient, Heat Removed by the Water ... 92




Figure 1.1 Reserch Flowchart 4

Figure 1.2 Flowchart of Numerical Solution. 6

Figure 1.3 Flowchart of Experimental Study 7

Figure 2.1 (a) single microchannel with two short bifurcation plates and one long and (b) single microchannel with one short bifurcation and

two long plates (Xie, Li, Sunden, Zhang, & Li, 2014). 13 Figure 2.2 Schematic layout of microchannel heat sink and heat source

(Laxmidhar Biswal & Som, 2009) 14

Figure 2.3 Micro-channel heat sinks with (a) rectangular,

(b) inverse-trapezoidal, (c) triangular, (d) trapezoidal, and

(e) diamond-shaped cross-sections (Kim & Mudawar, 2010). 14 Figure 2.4 A Schematic of a heat exchange unite with (a) zigzag channels,

(b) curvy channels, (c) step channels (Mohammed, Gunnasegaran,

& N.H., 2011). 16

Figure 2.5 Heat sink geometries (Jajja, Ali, Ali, & Ali, 2014). 18 Figure 2.6 Schematic shows different locations of inlet/outlet (Xia, Jiang,

Wang, Zhai, & Ma, 2015). 18

Figure 2.7 Shows the header design of microchannel heat sinks (Xia, Jiang,

Wang, Zhai, & Ma, 2015). 18

Figure 2.8 Geometrical Configurations Presented in the Introduction

(Latour, Bouvier, & Harmand, 2011) 20

Figure 2.9 Test samples: (a) finned metal foam (FMF) heat sinks;

(b) metal foam (MF) heat sinks (a, Kuang, Wena, Lu, & Ichimiya,

2014) 21

Figure 2.10 Schematics of heat sink assemblies: (a) vertical fins and

(b) oblique fins (Lin, Chuang, & Chou, 2005). 21 Figure 2.11 All Tested Heat Sinks in the Investigation (Wang, Yang, Liu,

& Chen, 2011). 22



Figure 2.12 Cylindrical Heat Sink for an LED Light Bulb (Jang, Park,

Yook, & Lee, 2014) 23

Figure 2.13 Front view of the flow channel (Kong & Ooi, 2013). 24 Figure 2.14 Completed sample with radial channels (Takács, P.G.Szabó,

B.Plesz, & Gy.Bognár, 2014) 26

Figure 2.15 Schematic of the microchannel heat sink: (a) system, (b) microscope image of silicon microchannels, and (c) geometric shape of microchannel (Chen, Zhang,

Shi, & Wu, 2009). 28

Figure 2.16 Experimental Setup of the three dissipation modes (a) metal foam–PCM composite; (b) pure PCM; (c) solid basement

(Qu, Li, Wang, & Tao, 2012). 29

Figure 2.17 Grooved wall (Xia, Zhai, & Cui, 2013). 31

Figure 2.18 Illustration of the Attachment of An Inclined Plate Shield to

A Plate-Fin Heat Sink (Tsai, Li, & Lin, 2010). 32 Figure 2.19 (a) Heat sink with vortex generators, (b) vortex generators

in common-flowup configuration, and (c) vortex generators in common-flow-down configuration (Li H.-Y. , Chen, Chao,

& Liang, 2013). 32

Figure 2.20 Schematic of the Integrated System (Yu Y. , et al., 2014). 33 Figure 2.21 The Schematic of (a) Offset Strip-Fin Microchannels; and

(b) The Computational Domain of the One Unit of Microchannels

(Hong & Cheng, 2009) 34

Figure 2.22 Embossed Fin Geometry (Singh & Patil, 2015). 35

Figure 3.1 Mini-Channel Heat sink Geometry. 38

Figure 3.2 Embossed Impressions 38

Figure 3.3 Height and Width of a Channel 39

Figure 3.4 3D Boundaries. 45

Figure 3.5 3D Meshing of Heat Sink. 47

Figure 3.6 Residuals of Smooth and Embossed MCHS 48

Figure 3.7 Temperature Value at Middle of the MCHS. 48

Figure 3.8 Base Temperature of Smooth Heat Sink. 49

Figure 3.9 Flow Chart of the Experimental Design and Runs 51



Figure 3.10 Surface Roughness Measuring Machine 51

Figure 3.11 Geometries of Smooth and Embossed MCHS 53

Figure 3.12 Copper Electrode. 55

Figure 3.13 Scheme of the Experimental Cooling System. 57

Figure 3.14 Electrical Heater Inserted Inside Acrylic Glass Block (40 mm

Length and 40 mm Width) 58

Figure 3.15 Final Product of MCHS and Embossed MCHC with

40x40 mm Dimensions. 59

Figure 3.16 Pump Inside the Water (Reservoir) 60

Figure 3.17 SP-7800 Pump 61

Figure 4.1 Meshing in 3D Geometry 68

Figure 4.2 Grid Independence Study 69

Figure 4.3 Minichannel Heat Sinks Flat Plate (A), spacing =0.2mm (B), spacing=0.5mm (C) and spacing= 1mm

(D), spacing 0.2 mm and height= 5mm (E). 70

Figure 4.4 Boundaries and Heat Sink Geometry 71

Figure 4.5 Heat Sink Geometry 71

Figure 4.6 Comparison of Temperature Drop with Volumetric Fow Rate 72 Figure 4.7 Comparison of Base Temperature with Volumetric Fow Rate. 73 Figure 4.8 Comparison of Heat Transfer Rate with Volumetric Flow Rate 74 Figure 4.9 Variation of Thermal Resistance of Heat Sinks with Volumetric

Fow Rate 75

Figure 4.10 Overall Heat Transfer Coefficient of Heat Sinks with

Volumetric flow Rate 76

Figure 4.11 Heat Transfer Area Enhancement and the Average Enhancement

with Fins Spacing 76

Figure 4.12 Overall Heat Transfer Coefficient of Heat Sinks with Volumetric

flow Rate 77

Figure 4.13 Overall Heat Transfer Coefficient of Heat Sinks with Volumetric

flow Rate 78



Figure 4.14 Variation of Thermal Resistance of Heat Sinks with Volumetric

Flow Rate 78

Figure 4.15 Temperature Distribution at heights= 3, 5mm and Mass Flow

Rate 1 LPM 80

Figure 4.16 Streamlines of Velocity at heights= 3, 5mm and Mass Flow

Rate 1 LPM 81

Figure 4.17 Temperature Distribution at heights= 3, 5mm & Mass Flow

Rate 0.5 LPM 82

Figure 4.18 Streamlines of Velocity at Heights= 3, 5mm and Mass Flow

Rate 0.5 LPM 82

Figure 4.19 Spacing=0.2mm(A), Spacing=1mm(B) and Embossed Fins,

Space 1mm(C) 84

Figure 4.20 Base temperature and Mass Flow Rate of Mini-Channel

Space=0.2mm Heat Sink. 85

Figure 4.21 Variation of Base Temperature of Heat Sinks with Volumetric

Flow Rate 87

Figure 4.22 Comparison of Heat Transfer Rate with Volumetric Flow Rate 88 Figure 4.23 Comparison of Heat Transfer Rate with Reynolds Number

As A Function of Fin Spacing 88

Figure 4.24 Comparison of Temperature Drop with Volumetric Flow Rate 89 Figure 4.25 Overall Heat Transfer Coefficient of Heat Sinks with Volumetric

flow Rate 90

Figure 4.26 Variation of Thermal Resistance of Heat Sinks with Volumetric

Flow Rate 91

Figure 4.27 Variation of Overall Heat Transfer Coefficient with Volumetric

Flow Rate 91

Figure 4.28 Comparison of Active Area Enhancement with Different Fins

Spacing And Embossed Fin 92

Figure 4.29 Triangular Embossed Impression Mini-Channel Heat Sink 94 Figure 4.30 Rectangular Embossed Impression Mini-channel Heat Sink 94 Figure 4.31 Semicircle Embossed Impression Mini-Channel Heat Sink. 95

Figure 4.32 Base Temperature with Re 96

Figure 4.33 Heat Removed with Re 96



Figure 4.34 Overall heat Transfer with Re 97

Figure 4.35 Variation of Thermal Resistance of Heat Sinks with Re 98 Figure 4.36 Rectangular at 45 (A), Triangular at 45 (B), Rectangular

at 90 (C), Triangular at 90 (D Embossed Impression Mini-

Channel Heat Sink 99

Figure 4.37 Flow Direction and Angle of Attack 100

Figure 4.38 Meshing in 3D Geometry Embossed Angle is 30 101 Figure 4.38 Temperature Plot at the Base, Triangular Embossed Impression,

Angle 30 and Reynolds 1950 101

Figure 4.39 Residual Plot, Triangular Embossed at 30 102

Figure 4.41 Base Temperature with Embossed Impressions Angle 103 Figure 4.42 Heat Removed with Embossed Impressions Angle 103 Figure 4.43 Overall Heat Transfer with Embossed Impressions Angle 104 Figure 4.44 Variation of Thermal Resistance of Heat Sinks with Embossed

Impressions Angle 105

Figure 4.45 Streamlines of Velocity at Rectangular Embossed, Angle 30

at Reynolds 1950 106

Figure 4.46 Streamlines of Velocity at Rectangular Angle 45 at Reynolds 1950 107 Figure 4.47 Streamlines of Velocity at Rectangular Embossed and Angle 90

at Reynolds 1950 107

Figure 4.48 Streamlines of Velocity at Triangular Embossed and Angle 30

at Reynolds 1950 108

Figure 4.49 Streamlines of velocity at Triangular embossed and angle 45

at Reynolds 1950. 108

Figure 4.50 Streamlines of Velocity at Triangular Embossed and Angle 90

at Reynolds 1950 109

Figure 4.51 Temperature Distribution and Velocity Streamlines on the MCHS

at Re= 776 111

Figure 4.52 Temperature Distribution and Velocity Streamlines on the MCHS

at Re= 1249 111

Figure 4.53 Temperature Distribution and Velocity Streamlines on the Mchs

At Re= 2900 112



Figure 4.54 Base Temperature with Re 113

Figure 4.55 Outlet Temperature with Re 114

Figure 4.56 Temperature Drop with Re. 115

Figure 4.57 Heat Removed by the Water Circulating through the Heat Sink

with Re 116

Figure 4.58 Heat Transfer Coefficient with Re 117

Figure 4.59 Thermal Resistance with Re 118

Figure 4.60 Pressure with Re 118

Figure 4.61 Power Consumption with Re 119




A Area, m2

AR Aspect ratio

Cp Specific heat capacity, J/kg.K Dh Hydraulic diameter, m

DW Distilled water

f Fanning friction factor

g Gravitational acceleration, m/s2

h Convection heat transfer coefficient, W/m2. ºC H Channel height, m

HE Heat exchanger

HTE Heat transfer enhancement

I Current, A

k Thermal conductivity, W/m. ºC L, l Channel Length, mm

M Molecular weight, g N Number of channels Nu Nusselt number P. P Pumping power, W Pr Prandtl number

∆𝑃 Pressure drop, Pa Q Heat flux, w/m2

Q Heat flux, W

R Thermal resistance, ºC/W.m2 Re Reynolds number

T Temperature, K

T Thickness, m

U Velocity, m/s

V Voltage, v

x, y, z 3D Cartesian coordinates

Greek symbols ρ Density, kg/m3

μ Dynamic viscosity, kg/m.s Subscripts

avg Average

f Fin

bf base fluid eff Effective

f Fluid

m Mean

w Water








The electronics industry is increasingly developing. Light, small, and high-power electronic components are becoming more ubiquitous. Without efficient heat transfer, excessive temperatures may make the working performance of these components unstable, reducing their lifespan or even causing damage to them. Therefore, a major challenge in the design of electronic components is to enhance the efficiency of their heat transfer (Hung-Yi Li, 2013). Effective heat removal is required to keep substrate temperatures below critical temperatures at which devices will fail. Although liquid cooling with or without phase change are often regarded as the major candidates for high flux applications, air cooling is still by far the most common cooling technique for electronic cooling for its simplicity, reliability, and low cost.

The low thermal conductivity of air inevitably results in a very low heat transfer coefficient. As a consequence, the general approach for heat transfer improvement is via exploitation of smaller fin spacing to accommodate more fin surface. However, a limitation is imposed on this conventional approach when the fin spacing is small or when the operation speed is low (Chi-Chuan Wang, 2011). Fin geometry has a great role in making simple, economic and portable heat sink capable of dissipating maximum heat energy at a fixed heat load. The micro heat sink has good performance for electronics cooling at high heat fluxes, and it can improve the reliability and lifetime of electronic device. The full cannelure fin along with the dimple/cavity structure of heat sink could attain 25% increase of heat transfer with increasing in friction reduction of



about 20% (Chi-Chuan Wang, 2011). Moreover, converse to those interrupted fin or triangular vortex generator, it is found that their proposed fin structure still offers significant augmentation in fully developed region.

The effect of shape, position and other parameters of vortex generators on the thermal and hydraulic performance of heat sink was studied by Timothy The result has highlighted that the attack angle of generators play an important role in the heat transfer augmentation of heat sinks (Timothy Dake, 19-23 July 2009). Moreover, when the vortex generator height, the heat transfer improves and the greater improvement was registered when the generator and channel heights are equal. Compared to K.S. Yang, 2010 has denoted that the vortex generators could enhance the thermal performance of heat sink. It is found that the vortex generators operated at a higher frontal velocity and at a larger fin pitch are more beneficial than that of plain fin heat sink (K.S. Yang, 2010).

There were many studies available in the literature related to the role of fin configuration in enhancing the convective heat transfer through the fin. (Starner & McManus, 1963) Studied four different fin arrays and three different base plates to compute natural convective heat transfer coefficients with regard to varied fin spacing and the fin height.

Welling, 1965 found that the vertically based fin array orientation is superior among all types of fin arrays with comparable fin heights. The variation of temperature with the change in the fin height to fin spacing ratio was discussed and an equation for optimum value of the fin height to fin spacing ratio was proposed. Chaddock, 1970 varied the fin spacing and the fin height in the large vertically based fin arrays and found that the radiation mode contributes about 20% of the total heat transfer. In a study by (Alhara, 1970), the effect of fin geometry and temperature on average heat transfer coefficient has been studied and an empirical correlation was obtained.

The dissipative heat flux from power electronic devices has risen significantly in the past few years. Whereas, the power consumption trend shows that the relentless



increase in heat density will keep on rising at the device, module and system level with advancement of technology. Conventional forced air cooled designs are no longer adequate to remove heat fluxes higher than 100 W/cm2 since they are beyond the current limits of air-cooling technology. Therefore, advanced cooling solutions are in demand for the thermal management of next-generation power electronics.


The overheating in the heated walls of channels is an essential problem in any heat exchanger. Because the industrial companies of computers are going to minimize the size and increasing the performance of the chips. In the electronic chips, the increasingly improvement of the processers speed leads to generates more heats. So, it requires an appropriate heat sink to absorb the heat generated by the processers. It became very important to improve the thermal performance of the heat sinks by enhancing their ability for heat absorption while maintaining or reducing the size of the heat sink.


This research concentrated on the following aims:

i. To study the effect of the base size, the space between fins, the height of fin and the thickness of the fin on the thermal performance of the mini- channel heat sink.

ii. To investigate the embossed impressions effect on the thermal performance of Mini-channel heat sink and the flow behavior numerically and experimentally.

iii. To enhance the heat transfer of the Mini-channel heat sink by using different embossed impressions shapes and angles.



Numerical and experimental techniques are used to achieve the objectives in this research. For more details:

Figure 1.1 illustrates the research flow chart. It starts by reporting, discussing, studying, comparing and analyzing the literature review. Then, numerical investigation was performed to carry out the parametric study and validated by published data from open literature. Fabrication and experimental setting up have been done, simulation study was carried out to validate and confirm the experimental results.

Figure 1.1 Reserch Flowchart Writing up thesis


Literature Review

Numerical Analysis

Validation with Literature

Experimental study

CFD analysis to validate with experiments



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