ISSN Online: 2377-424X
ISBN Print: 1-56032-797-9
International Heat Transfer Conference 11
FORCED-CONVECTION AND BOILING CHARACTERISTICS IN MICROCHANNELS
要約
A sequence of experiments was conducted to investigate the
fluid flow and heat transfer characteristics in microchannels with/without phase-change in last few years. More attentions have been paid to understand the flow boiling heat transfer performance and phase-change transition mechanism in micochannels. In these experiments, the single-phase and flow boiling heat transfer of pure water, pure methanol and watermethanol
binary mixtures flowing through eight rectangular and
six triangular microchannels were observaed and measured.
The microchannel size, geometrical configuration, and mole
fraction of water-methanol binary mixtures were experimentally found to have critically significant impact on single-phase forced-eonvection, on flow boiling, especially nucleate boiling, and on bubble formation and growth in microchannels. A physical model accounting for the effect of channel size was proposed to theoretically analyzed the single-phase gas flow and heat transfer through microtubes. For flow boiling and nucleation in microchannels, two new concepts "evaporating
space" and "fictitious boiling" were proposed to explain the unusual phase-ehange transport phenomena. A dimensionless number and related criterion, for determining the phase transition in microchannels, were derived theoretically. The dynamical analyses of the system indicated that nucleate boiling in microchannels is almost impossible, and the nature of this transport phenomenon is found to be thermodynamic nonequilibrium.