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

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The film flow measurements listed in tables A4-A6 are
performed with an adiabatic length of 0.5, 1.0 and 2.0 m. This
was carried out by moving both upper and lower clamps while the
distance between them was fixed. The purpose of these measurements
was to investigate how rapidly the equilibrium situation
was achieved after the diabatic length. Some of the results are
shown in fig. 3.18. Again it is seen that, for low values of
x , the diabatic film flow rate exceeds the adiabatic.
3.3.1.3. Diabatic Data for Test Section 17/26S. This set of
diabatic measurements was basically performed to investigate
the influence on the film of the relative distribution of heat
flux on the two walls. In figs. 3.19.a-b some of the measurements
of film flow rates are shown versus the outlet quality.
A comparison is made with some of the measurements reported by
Jensen and Mannov (1974). These measurements were carried out
in the same test section, but at the high pressure water loop
at the Royal Institute of Technology in Stockholm. The good
agreement observed checks the measuring system and gives an
impression of the reproducibility of the measurements.
To illustrate the transition from the slug flow regime, a
few measurements were carried out at very low outlet steam
2
qualities. These measurements for G = 1000 kg/m s, q," = q-" =
45 H/cm , show that the entrainment increases when the slug
flow regime is approached. Furthermore, it is indicated that the
ratio between the film flow rates per unit perimeter tends to
unity when x. tends to zero.
The influence of the relative heat flux distribution on the
rod and tube wall is shown in figs. 3.20.a-b. The corresponding
adiabatic values from table A7 are also included. The other
data in table Al show similar deviations from the adiabatic,
equilibrium film flow rates.
3.3.2. Axial Pressure Gradients
The axial pressure gradients are determined from the pressure
drop measurements described in sect. 3.2.3.
The pressure drop measured between the pressure taps 1 and i+1
is designated Ap.. The total axial pressure gradients in the
midpoints between the taps are determined by subtraction of the