An Experimental and Theoretical £ Investigation of Annular Steam ...
An Experimental and Theoretical £ Investigation of Annular Steam ...
An Experimental and Theoretical £ Investigation of Annular Steam ...
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- 8 -<br />
The (total) mass flux G(kg/m 2 s) is defined by the ratio:<br />
« * 5 • (2.4)<br />
The mean velocity <strong>of</strong> the gas u (m/s) is related to G through<br />
g<br />
u - - mx _ Gx<br />
9 ' °g A g " p g A g " V<br />
where p (kg/m ) is the density <strong>of</strong> the gas.<br />
The relationship between the mass flux <strong>and</strong> the mean velocity<br />
<strong>of</strong> the liquid (film <strong>and</strong> entrainment) u,(m/s) is developed in a<br />
similar way:<br />
u = mi = nd-x) _ G(l-x) ._ ,,<br />
U l PlA x Pl A x " pjd-o)<br />
U ' 6)<br />
where p^(kg/m ) is the density <strong>of</strong> the liquid.<br />
The ratio between u <strong>and</strong> u, is denominated the mean slip<br />
ratio S(-):<br />
u , p,<br />
S = -2 = -*_ il« _i ,2 71<br />
" u,<br />
X " x a p g *<br />
( ' J<br />
2.3. Previous <strong>Experimental</strong> Work<br />
2.3.1. Measurements <strong>of</strong> Film Flow Rates<br />
Measurements <strong>of</strong> the liquid film flow rate by extraction <strong>of</strong><br />
the film through a permeable section <strong>of</strong> the channel have been<br />
carried out through several years.<br />
In some <strong>of</strong> the earliest investigations (Bennet <strong>and</strong> Thornton<br />
(1961)i Collier <strong>and</strong> Hewitt (1961)j Gill, Hewitt <strong>and</strong> Lacey (1965))<br />
a slit in the wall was used to divert the liquid film. These<br />
measurements were carried out with air-water in a perspex tube<br />
with an inner diameter <strong>of</strong> 31.8 mm. However, a disadvantage <strong>of</strong><br />
the slit is that the large roll waves are likely to overshoot<br />
the rather narrow gap. Therefore poreous sinters or perforated<br />
wall sections with a length <strong>of</strong> app. 5 cm were used in the later<br />
studies.<br />
The film flow rate is measured by an estimation <strong>of</strong> the<br />
liquid <strong>and</strong> the gas flow rate in the extracted mixture. In a<br />
two-component system (e.g. air-water) this is done by means <strong>of</strong><br />
a cyclone separator (cf. e.g. Bennet <strong>and</strong> Thornton (1961)). For