1 Introduction 1
1.1 Research Background and Proposal of Topics 1
1.1.1 Condensation 1
1.1.2 Frosting and Icing 2
1.1.3 Proposal of Topics 3
1.2 Research Status 4
1.2.1 Fabrication of Superhydrophobic Surfaces 5
1.2.2 Condensation and Droplet Behaviors on
Superhydrophobic Surfaces 8
1.2.3 Frost/Ice Melting and Droplet Behaviors
on Superhydrophobic Surfaces 15
1.2.4 Summary of Research Status 17
1.3 Research Contents of Present Work 18
References 19
2 Experimental System and Superhydrophobic Surfaces 27
2.1 Experimental System and Data Processing 27
2.1.1 Overview of Experimental System 27
2.1.2 Data Processing Methods 30
2.2 Fabrication and Characterization of Superhydrophobic Surfaces . 31
2.2.1 Fabrication Methods of Superhydrophobic Surfaces 31
2.2.2 Al-Based Superhydrophobic Surfaces 32
2.2.3 Cu-Based Superhydrophobic Surfaces 36
2.3 Selection of Superhydrophobic Surfaces for Experiments 39
2.4 Summary 40 References . 41 3 Behaviors of Condensed Droplets on Superhydrophobic Surfaces . 43 3.1 Experimental Surfaces and Conditions . 43 3.2 Condensed Droplet Behaviors on Superhydrophobic Surfaces 44 3.2.1 Immobile Droplet Coalescence . 44
XVI Contents 3.2.2 Self-propelled Droplet Jumping 45
3.2.3 Self-propelled Droplet Sweeping 46
3.3 Statistics of Condensed Droplet Behaviors on Superhydrophobic
Surfaces 49
3.4 Critical Conditions for Self-propelled Droplet Behaviors 51
3.4.1 Theoretical Model 52
3.4.2 Minimum Critical Droplet Radius 54
3.4.3 Critical Ratio of Droplet Radius 56
3.4.4 Critical Static Contact Angle 57
3.5 Effect of Self-propelled Droplet Behaviors on Droplet Growth . 58
3.5.1 Droplet Diameter Distribution 58
3.5.2 Average Droplet Diameter 61
3.5.3 Surface Coverage Fractions 62
3.5.4 Effects of Working Conditions 63
3.6 Summary 64
References 65
4 Numerical Simulations of Multi-droplet Coalescence-Induced
Jumping 67
4.1 Simulation Objects and Conditions 68
4.2 Mathematical Model 69
4.2.1 Control Equation 69
4.2.2 Computational Domain, Boundary Conditions,
and Grids 71
4.2.3 Energy Analysis 72
4.3 Model Validation—Two-Droplet Coalescence-Induced Jumping . 73
4.4 Multi-droplet Coalescence-Induced Droplet Jumping 76
4.4.1 Effect of Coalesced Droplet Number 76
4.4.2 Effect of Droplet Position Distribution 81
4.5 Summary 87
References 87
5 Dynamic Melting of Freezing Droplets on Superhydrophobic
Surfaces 89
5.1 Experimental Surfaces and Conditions 89
5.2 Freezing of Condensed Droplets on Superhydrophobic Surfaces . 91
5.3 Self-propelled Behaviors During Melting Process of Freezing
Droplets 94
5.3.1 Melting Droplet Rotating 94
5.3.2 Melting Droplet Jumping 96
5.3.3 Melting Droplet Sliding 97
5.4 Effects of Self-propelled Melting Droplet Behaviors on Surface Coverage Fraction 99
5.5 Summary of This Chapter 101
References 102 Contents XVII
6 Meltwater Evolution During Defrosting on Superhydrophobic
Surfaces 105
6.1 Experimental Surfaces and Conditions 105
6.2 Meltwater Evolution on Superhydrophobic Surfaces 107
6.3 Edge Curling Phenomenon of Meltwater Films 109
6.4 Non-breaking Phenomenon of Chained Droplets 110
6.5 Summary 113
References 114
7 Relation Between Surface Wettability and Droplet Behaviors,
and Hysteresis Number 117
7.1 Morphologies and Behaviors of Condensed Droplets and Melted
Droplets 117
7.1.1 Morphologies and Behaviors of Condensed Droplets 117
7.1.2 Morphologies and Behaviors of Melted Droplets 120
7.2 Relation Between Surface Wettability and Droplet Behaviors 122
7.3 Hysteresis Number 126
7.4 Summary 129
References 130
8 Conclusions and Outlooks 133
8.1 Main Conclusions in the Present Work 133
8.2 Innovations in the Present Work 136
8.3 Outlooks for Future Research 137