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  • Sede Amministrativa: Universit degli Studi di Padova

    Dipartimento di Ingegneria Industriale

    SCUOLA DI DOTTORATO DI RICERCA IN: Ingegneria Industriale

    INDIRIZZO: Ingegneria dellEnergia

    CICLO: XXVI

    EXPERIMENTAL CHARACTERIZATION OF NANOFLUIDS AS HEAT TRANSFER MEDIA

    Direttore della Scuola: Ch.mo Prof. Paolo Colombo

    Coordinatore dindirizzo: Ch.mo Prof. Luisa Rossetto

    Supervisore: Prof. Claudio Zilio

    Dottorando: Laura Colla

  • Contents

    I

    EXPERIMENTAL CHARACTERIZATION OF

    NANOFLUIDS AS HEAT TRANSFER MEDIA

    Contents

    Chapter 1. Introduction.1

    1.1 Thesis objectives and outline ................................................................................. 1

    1.2 Background and literature review .......................................................................... 2

    1.2.1 Why nanofluids are studied ......................................................................................... 5

    1.2.2 Uses of nanofluids ....................................................................................................... 5

    1.2.3 Challenges of nanofluids ............................................................................................. 6

    1.2.4 Open questions on nanofluids ..................................................................................... 6

    Chapter 2. Preparation and characterization of nanofluids ..9

    2.1 How to prepare nanoparticles ................................................................................ 9

    2.1.1 Carbon structures ...................................................................................................... 11

    2.1.2 Core-shell structures.................................................................................................. 12

    2.2 How to prepare nanofluids ................................................................................... 12

    2.3 Parameters affecting nanofluids properties .......................................................... 14

    2.4 Mean dimension of nanoparticles ........................................................................ 14

    2.5 Nanofluids stability characterization ................................................................... 16

    2.5.1 DLS measurements ................................................................................................... 16

    2.5.2 potential measurements .......................................................................................... 17

  • Contents

    II

    2.5.3 pH measurements ...................................................................................................... 18

    Chapter 3. Experimental apparatus and procedures........21

    3.1 Experimental dynamic viscosity measurements ................................................... 21

    3.1.1 Viscosity of suspensions ........................................................................................... 24

    3.1.2 Measurements of water dynamic viscosity ............................................................... 25

    3.2 Thermal conductivity measurements .................................................................... 27

    3.2.1 Thermal conductivity of suspensions ........................................................................ 30

    3.2.2 Measurements of water thermal conductivity ........................................................... 32

    3.3 Conclusions .......................................................................................................... 34

    Chapter 4. Convective heat transfer ..........37

    4.1 State of the art ....................................................................................................... 37

    4.2 Apparatus design and construction ....................................................................... 38

    4.2.1 Radial conduction through the pipe ........................................................................... 47

    4.3 Calibration ............................................................................................................ 48

    4.3.1 Thermocouples calibration ........................................................................................ 49

    4.4 Water convection testing ...................................................................................... 51

    4.5 Uncertainty analysis ............................................................................................. 56

    4.6 Conclusions .......................................................................................................... 57

    Chapter 5. Water based TiO2 nanofluid characterization...61

    5.1 Nanofluid preparation ........................................................................................... 61

    5.2 Nanofluids stability characterization .................................................................... 61

    5.3 Thermal conductivity ............................................................................................ 63

    5.4 Dynamic Viscosity ............................................................................................... 66

    5.5 Comparison with published literature .................................................................. 67

    5.5.1 Thermal conductivity ................................................................................................ 68

  • Contents

    III

    5.5.2 Dynamic viscosity ..................................................................................................... 69

    5.6 Conclusions .......................................................................................................... 70

    Chapter 6. Water based SWCNH nanofluid characterization.....73

    6.1 Nanofluid preparation .......................................................................................... 73

    6.2 Nanofluids stability characterization ................................................................... 75

    6.3 Dynamic Viscosity ............................................................................................... 76

    6.4 Comparison with published literature .................................................................. 78

    6.5 Thermal conductivity ........................................................................................... 80

    6.6 Conclusions .......................................................................................................... 82

    Chapter 7. Water based SiO2 nanofluid characterization85

    7.1 Nanofluid preparation .......................................................................................... 86

    7.2 Nanofluids stability characterization ................................................................... 86

    7.3 Thermal conductivity ........................................................................................... 87

    7.4 Dynamic Viscosity ............................................................................................... 89

    7.5 Comparison with published literature .................................................................. 92

    7.6 Conclusions .......................................................................................................... 92

    Chapter 8. Water based Fe2O3 nanofluid characterization..95

    8.1 Nanofluid preparation .......................................................................................... 95

    8.2 Nanofluids stability characterization ................................................................... 96

    8.3 Thermal conductivity ........................................................................................... 97

    8.4 Dynamic viscosity ................................................................................................ 99

    8.5 Comparison with literature ................................................................................ 101

    8.5.1 Thermal conductivity .............................................................................................. 101

    8.5.2 Dynamic viscosity ................................................................................................... 102

    8.6 Conclusions ........................................................................................................ 103

  • Contents

    IV

    Chapter 9. Water based ZnO nanofluid characterization..107

    9.1 Nanofluid preparation ......................................................................................... 107

    9.2 Nanofluids stability characterization .................................................................. 107

    9.3 Thermal conductivity .......................................................................................... 109

    9.4 Dynamic Viscosity ............................................................................................. 111

    9.5 Heat transfer coefficient ..................................................................................... 114

    9.6 Comparison with published literature ................................................................ 120

    9.6.1 Thermal conductivity .............................................................................................. 120

    9.6.2 Dynamic viscosity ................................................................................................... 120

    9.6.3 Heat transfer coefficient .......................................................................................... 120

    9.7 Conclusions ........................

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