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Abstract
In this paper, flow boiling phenomenological differences between micro- and macroscale channels are discussed. Analyses of flow pattern results are performed in order to identify the main differences between micro- and macroscale phenomena. Based on these analyses, important flow pattern differences between micro- and macroscale behaviors are identified, and new phenomenological transition criteria based on flow patterns are presented. These criteria are based on the existence of stratified flow and on the degree of uniformity of the liquid film along the tube perimeter during annular flow.
NOMENCLATURE
| Bo | = | Bond number (—) |
| Co | = | confinement number (—) |
| D | = | tube diameter, (m) |
| Eo | = | Eotvos number (—) |
| Fp | = | pressure force, (N) |
| Fst | = | surface tension force, (N) |
| g | = | gravitational acceleration, (m s−2) |
| G | = | mass velocity, (kg m−2 s−1) |
| H | = | height (m) |
| Lo | = | Laplace length scale (m) |
| R | = | radius (m) |
| Re | = | Reynolds number (—) |
| y | = | length (m) |
Greek Symbols
| θ | = | contact angle (radians) |
| ρ | = | density, (kg m−3) |
| σ | = | surface tension, (N m−1) |
| δ0 | = | film thickness in the bottom of the tube (m) |
| δm | = | film thickness in the bottom of the tube (m) |
Subscripts
| eq | = | equation |
| grav | = | gravitational |
| i | = | inertia |
| l | = | liquid |
| m | = | momentum |
| v | = | vapor |
| τ | = | shear |
Additional information
Notes on contributors
Cristiano B. Tibiriçá
Cristiano B. Tibiriçá has a bachelor's degree in mechanical engineering from University of São Paulo (USP), Brazil. He received his Ph.D. from USP, and worked during one year as a doctoral assistant at the Laboratory of Heat and Mass Transfer at the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, as part of his doctoral program. His research interests cover two-phase flow, boiling and condensation of external and internal flow, flow boiling instabilities, and convective evaporation and condensation in microscale channels.
Gherhardt Ribatski
Gherhardt Ribatski is a professor in the Department of Mechanical Engineering at the University of São Paulo (USP), Brazil. He received his Ph.D. from the University of São Paulo, Brazil, in 2002. He was a postdoctoral researcher in the Department of Industrial Engineering at the University of Illinois at Urbana–Champaign and in the Laboratory of Heat and Mass Transfer at the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland. His research interests cover nanofluids, pool boiling, falling-film evaporation and condensation, two-phase flow, boiling and condensation of external and internal flows, and convective evaporation and condensation in microscale channels. He has had more than 100 papers on two-phase flow and heat transfer published in conferences and journals.