Adiabatic two-phase frictional pressure drops in microchannels
Two-phase pressure drops were measured over a wide range of experimental test conditions in two sizes of microchannels (sight glass tubes 0.509 and 0.790 mm) for two refrigerants (R-134a and R-245fa). Similar to the classic Moody diagram in single-phase flow, three zones were distinguishable when pl...
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Veröffentlicht in: | Experimental thermal and fluid science 2007-07, Vol.31 (7), p.673-685 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Two-phase pressure drops were measured over a wide range of experimental test conditions in two sizes of microchannels (sight glass tubes 0.509 and 0.790
mm) for two refrigerants (R-134a and R-245fa). Similar to the classic Moody diagram in single-phase flow, three zones were distinguishable when plotting the variation of the two-phase friction factor versus the two-phase Reynolds number: a laminar regime for
Re
TP
<
2000, a transition regime for 2000
⩽
Re
TP
<
8000 and a turbulent regime for
Re
TP
⩾
8000. The laminar zone yields a much sharper gradient than in single-phase flow. The transition regime is not predicted well by any of the prediction methods for two-phase frictional pressure drops available in the literature. This is not unexpected since only a few data are available for this region in the literature and most methods ignore this regime, jumping directly from laminar to turbulent flow at
Re
TP
=
2000. The turbulent zone is best predicted by the Müller-Steinhagen and Heck correlation. Also, a new homogeneous two-phase frictional pressure drop has been proposed here with a limited range of application. |
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ISSN: | 0894-1777 1879-2286 |
DOI: | 10.1016/j.expthermflusci.2006.07.001 |