An Experimental and Theoretical £ Investigation of Annular Steam ...

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A tube with an internal diameter of 13.3 mm was used in the
experiments by Nigmatulin, MalyshenVo and Shugaev (1976). These
adiabatic measurements were mainly performed at 50 bar, but
results as 10, 20, 30, 70 and 100 bar are also reported.
It is seen that all experiments in tubes with steam-water
at high pressures until now have been carried out with diameters
of approximately 13 am. One of the main objectives of the present
work is to investigate the influence of geometry on annular
flow. Thus in the present report film flow measurements in
tubular test sections with internal diameters of 10 and 20 mm
are presented.
Film flow measurements in an annular test section with steamwater
mixtures were perfarmed by Noeck (1970). The experiments
were carried out in a concentric annulus at 35 and 69 bar. The
rod diameier was 19.7 mm and the internal tube diameter 23.8 mm.
The total length of the test section was 2.9 m. Most of the
experiments were performed under diabatic conditions with a
movable heater inside the rod. However, also a few measurements
were carried out under adiabactic conditions. These measurements
showed that the tube carried such more liquid per unit perimeter
than the rod film. This asymmetry was also detect id in the
adiabatic experiments by Hannov (1973b). Here the test section
consisted of a 17.0 mm rod mounted concentrically inside a
27.2*mm tube. The total length of this test section was 3.5 m.
Due to the relatively short lengths of the two annuli, it
was not absolutely certain that the flow was fully developed,
i.e. that the equilibrium situation was reached in the experiments.
However, the present adiabatic measurements in a long
(8 m) annulus (17 0 /26*mm) confirm that the asymmetry is present
in the equilibrium situation.
The first diabatic measurements in annuli with both a heated
rod and tube wall were performed by Jensen and Nannov (1974) in
a 3.5 m long annulus (17*/26*mm). This investigation of the
Influence of the relative heat flux distribution on the film
flow rates is continued in the present work.
Finally, it should be mentioned that Andersen et al. (1974)
measured the circumferential film flow distribution in an
eccentric annulus with steam-water mixtures. Kere it appeared
that the minimum film flow rate occured at the minimum gap. A
similar result was achieved by Schraub et al. (1969) with air-