Heat Transfer and Fluid Flow in Minichannels and Microchannels (eBook)

Cover 1
Heat Transfer and Fluid Flow in Minichannels and Microchannels 4
Contents 6
About the Authors 7
Preface 9
Nomenclature 11
Greek Symbols 18
Subscripts 21
Superscripts 23
Operators 23
Chapter 1. Introduction 24
1.1. Need for smaller flow passages 24
1.2. Flow channel classification 25
1.3. Basic heat transfer and pressure drop considerations 26
1.4. Special demands of microscale biological applications 28
1.5. Summary 29
1.6. Practice problems 29
References 30
Chapter 2. Single-phase gas flow in microchannels 32
2.1. Rarefaction and wall effects in microflows 33
2.1.1. Gas at the molecular level 33
2.1.1.1. Microscopic length scales 33
2.1.1.2. Binary intermolecular collisions in dilute simple gases 34
2.1.2. Continuum assumption and thermodynamic equilibrium 37
2.1.3. Rarefaction and Knudsen analogy 40
2.1.4. Wall effects 41
2.2. Gas flow regimes in microchannels 43
2.2.1. Ideal gas model 44
2.2.2. Continuum flow regime 45
2.2.2.1. Compressible Navier–Stokes equations 45
2.2.2.2. Classic boundary conditions 46
2.2.3. Slip flow regime 46
2.2.3.1. Continuum NS–QGD–QHD equations 47
2.2.3.2. First-order slip boundary conditions 48
2.2.3.3. Higher-order slip boundary conditions 51
2.2.3.4. Accommodation coefficients 52
2.2.4. Transition flow and free molecular flow 53
2.2.4.1. Burnett equations 53
2.2.4.2. DSMC method 59
2.2.4.3. Lattice Boltzmann method 60
2.3. Pressure-driven steady slip flows in microchannels 60
2.3.1. Plane flow between parallel plates 62
2.3.1.1. First-order solution 63
2.3.1.2. Second-order solutions 65
2.3.2. Gas flow in circular microtubes 67
2.3.2.1. First-order solution 67
2.3.2.2. Second-order solution 69
2.3.3. Gas flow in annular ducts 69
2.3.4. Gas Flow in rectangular microchannels 70
2.3.4.1. First-order solution 71
2.3.4.2. Second-order solution 72
2.3.5. Experimental data 76
2.3.5.1. Experimental setups for flow rate measurements 77
2.3.5.2. Flow rate data 79
2.3.5.3. Pressure data 85
2.3.5.4. Flow visualization 85
2.3.6. Entrance effects 86
2.4. Pulsed gas flows in microchannels 88
2.5. Thermally driven gas microflows and vacuum generation 90
2.5.1. Transpiration pumping 91
2.5.2. Accommodation pumping 92
2.6. Heat transfer in microchannels 93
2.6.1. Heat transfer in a plane microchannel 94
2.6.1.1. Heat transfer for a fully developed incompressible flow 94
2.6.1.2. Heat transfer for a developing compressible flow 96
2.6.2. Heat transfer in a circular microtube 96
2.6.3. Heat transfer in a rectangular microchannel 96
2.7. Future research needs 97
2.8. Solved examples 97
2.9. Problems 102
References 104
Chapter 3. Single-phase liquid flow in minichannels and microchannels 110
3.1. Introduction 110
3.1.1. Fundamental issues in liquid flow at microscale 110
3.1.2. Need for smaller flow passages 111
3.2. Pressure drop in single-phase liquid flow 113
3.2.1. Basic pressure drop relations 113
3.2.2. Fully developed laminar flow 114
3.2.3. Developing laminar flow 115
3.2.4. Fully developed and developing turbulent flow 118
3.3. Total pressure drop in a microchannel heat exchanger 119
3.3.1. Friction factor 119
3.3.2. Laminar-to-turbulent transition 124
3.4. Roughness effects 125
3.4.1. Roughness representation 125
3.4.2. Roughness effect on friction factor 127
3.4.3. Roughness effect on the laminar-to-turbulent flow transition 131
3.4.4. Developing flow in rough tubes 132
3.5. Heat transfer in microchannels 132
3.5.1. Fully developed laminar flow 132
3.5.2. Thermally developing flow 133
3.5.3. Agreement between theory and available experimental data on laminar flow heat transfer 135
3.5.4. Roughness effects on laminar flow heat transfer 136
3.5.5. Heat transfer in the transition and turbulent flow regions 137
3.5.6. Variable property effects 138
3.6. Microchannel and minichannel geometry optimization 139
3.7. Enhanced microchannels 141
3.8. Solved examples 144
3.9. Practice problems 154
Appendix A 155
References 156
Chapter 4. Single-phase electrokinetic flow in microchannels 160
4.1. Introduction 160
4.2. EDL field 161
4.3. Electroosmotic flow in microchannels 162
4.4. Experimental techniques for studying electroosmotic flow 168
4.5. Electroosmotic flow in heterogeneous microchannels 174
4.6. AC electroosmotic flow 180
4.7. Electrokinetic mixing 186
4.8. Electrokinetic sample dispensing 191
4.9. Practice problems 194
References 195
Chapter 5. Flow boiling in minichannels and microchannels 198
5.1. Introduction 198
5.2. Nucleation in minichannels and microchannels 199
5.3. Non-dimensional numbers during flow boiling in microchannels 204
5.4. Flow patterns, instabilities and heat transfer mechanisms during flow boiling in minichannels and microchannels 207
5.5. CHF in microchannels 217
5.6. Stabilization of flow boiling in microchannels 218
5.6.1. Pressure drop element at the inlet to each channel 218
5.6.2. Flow stabilization with nucleation cavities 220
5.7. Predicting heat transfer in microchannels 222
5.8. Pressure drop during flow boiling in microchannels and minichannels 226
5.8.1. Entrance and exit losses 226
5.9. Adiabatic two-phase flow 229
5.10. Practical cooling systems with microchannels 229
5.11. Solved examples 230
5.12. Practice problems 243
References 243
Chapter 6. Condensation in minichannels and microchannels 250
6.1. Introduction 250
6.1.1. Microchannel applications 250
6.1.2. Microchannel phenomena 252
6.1.3. Chapter organization and contents 253
6.2. Flow regimes 254
6.2.1. Adiabatic flow 255
6.2.1.1. Conventional tubes 255
6.2.1.2. Small circular channels 262
6.2.1.3. Narrow, high aspect ratio, rectangular channels 270
6.2.1.4. Insights from relevant microgravity work 272
6.2.1.5. Channels with D & #8810
6.2.1.6. Dependence on contact angle and surface properties 276
6.2.2. Condensing flow 277
6.2.3. Summary observations and recommendations 286
6.3. Void fraction 288
6.3.1. Conventional tubes 288
6.3.2. Small channels 295
6.3.3. Microgravity 299
6.3.4. Microchannels 300
6.3.5. Summary observations and recommendations 303
6.4. Pressure drop 304
6.4.1. Classical correlations 309
6.4.2. Condensation or adiabatic liquid–vapor studies (& #8764
6.4.3. Air–water studies (& #8764
6.4.4. Condensation studies (& #8764
6.4.5. Air–water studies (D[sub(h)] < &
6.4.6. Summary observations and recommendations 328
6.5. Heat transfer coefficients 329
6.5.1. Conventional channel models and correlations 337
6.5.1.1. Gravity-driven condensation 337
6.5.1.2. Shear-driven condensation 341
6.5.1.3. Multi-regime condensation 350
6.5.2. Condensation in small channels 362
6.5.3. Summary observations and recommendations 374
6.6. Conclusions 376
6.7. Exercises 415
References 418
Chapter 7. Biomedical applications of microchannel flows 432
7.1. Introduction 432
7.2. Microchannels to probe transient cell adhesion under flow 433
7.2.1. Different types of microscale flow chambers 434
7.2.2. Inverted systems: well-defined flow and cell visualization 435
7.2.3. Lubrication approximation for a gradually converging (or diverging) channel 438
7.3. Microchannels and minichannels as bioreactors for long-term cell culture 441
7.3.1. Radial membrane minichannels for hematopoietic blood cell culture 441
7.3.2. The Bioartificial liver: membranes enhance mass transfer in planar microchannels 443
7.3.3. Oxygen and lactate transport in micro-grooved minichannels for cell culture 445
7.4. Generation of normal forces in cell detachment assays 447
7.4.1. Potential flow near an infinite wall 448
7.4.2. Linearized analysis of uniform flow past a wavy wall 449
7.5. Small-bore microcapillaries to measure cell mechanics and adhesion 452
7.5.1. Flow cytometry 454
7.5.2. Micropipette aspiration 455
7.5.3. Particle transport in rectangular microchannels 456
7.6. Solved examples 457
7.7. Practice problems 460
References 461
Subject Index 466
A 466
B 466
C 466
D 467
E 467
F 468
G 468
H 469
I 469
J 469
K 469
L 469
M 470
N 470
O 471
P 471
Q 471
R 471
S 472
T 472
U 473
V 473
W 473
Y 473
Z 473