Experimental investigation of condensation heat transfer in microchannels.
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The thesis describes experiments aimed at measurement of heat-transfer
coefficients for condensation in a multi micro channel tube. Experiments were
performed with steam and R113, fluids chosen to cover a wide range of
thermophysical properties, in particular, surface tension which plays an important
role during condensation in small, non-circular channels.
The aluminum extruded condenser tube used had cooled length 748 mm and 13
parallel channels each with height 1.38 mm and width 1.41 mm. The upper and
lower outer surfaces were cooled separately by water in counter flow in channels
above and below the test tube. The mass flow rates in the two channels were
adjusted to be the same. Coolant temperatures were measured at 17 positions
along each of the coolant channels as well as at inlet and exit. An accurate direct
measurement of the overall inlet-to-outlet coolant temperature difference was also
measured directly with a 10 junction thermopile for each of the two coolant
streams with junctions downstream of mixers. Temperatures of the condenser tube
wall were measured at 10 positions on each of the upper and lower surfaces using
embedded thermocouples. Temperatures and pressures of the vapour were
measured in chambers at the inlet and outlet of vapour stream. Pressures were also
measured in the condenser channels just upstream and just downstream of the
cooled section.
Data have been obtained for cases where the vapour was saturated (for both steam
and R113) at inlet. Runs were made for complete and incomplete condensation
within the tube.
Earlier investigations are critically reviewed and seen to exhibit wide scatter and
disagreement. For reasons which will become clear in the thesis, the present
results cannot, unfortunately, be claimed to have superior accuracy and generally
fall within the ranges of earlier data. A new and innovative test section has been
designed and will be used in forthcoming experiments.
Authors
Su, QianCollections
- Theses [3930]