**3.2.2 Steam-water fluid mixing under high pressure**

The TPFIT was applied to steam water fluid mixing test (Yoshida, 2007). Calculated test channels used in these simulations are shown in Fig.10 (b). The calculation conditions are shown in Table 4. An irregular mesh division in the Cartesian system was adopted and two subchannels and the interconnection were formed by using obstacles as shown in Fig.13. The total number of effective control volumes was 2,647,400 respectively. A non-slip wall, constant exit pressure, and constant inlet velocity were selected as boundary conditions for each subchannel.

Fig. 13. Calculation meshes in channel cross section for steam-water fluid mixing test.

Development of Two-Phase Flow Correlation

for Fluid Mixing Phenomena in Boiling Water Reactor 301

Fig. 15. Measured and calculated pressure difference between subchannels.

Fig. 16. Measured and calculated pressure difference between subchannels.

calculated test channel to let out air-water two-phase flow smoothly.

were measured.

**3.2.3 Numerical simulation of air-water two-phase flow in modeled 2 subchannels**  The TPFIT code was applied to experimental analyses of the existing 2-channel fluid mixing experiments (Sumida, 1995), and comparisons between measured and calculated results were carried. In the experiments, the differential pressure between the subchannel at the center height of the mixing section and the exit air and water flow rate of each subchannel

Numerical analyses of air-water flow fluid mixing were applied between the length of - 100mm and +60mm from the lower edge of the mixing section in the flow direction of the test channel as shown in Fig.17 (a). The flow area is divided into two channels by a flat plate (partition plate). At the upper part of the partition plate, there was a narrow slit, through which the channels were connected. The flow channel was divided into 3 parts, developing section, mixing section and outlet section. The narrow slit was located in the mixing section, and fluid mixing was occurred at this section. The developing section was set up to get developed flow at inlet of the mixing section. The outlet section was located at top of the

○ Measured ● Predicted


Table 4. Steam-water flow calculation condition.

Fig. 14. Observed and calculated slug behavior of steam-water fluid mixing test around the interconnection.

The slug behaviors observed and calculated around the interconnection is shown in Fig.14. As shown in Fig.14 (a), a part of single steam slug in Ch.2 intrudes to the Ch.1 through the interconnection. Averaged slug length is about 56 mm, and observed major slug characteristic behavior is as follows.


As shown in Fig.14 (b), the occurrence of intrusion of steam from the Ch.2 to the Ch.1 can be effectively calculated, and the calculated amount of steam penetration into the interconnection looks quite similar to the observed one. Predicted slug length is about 59 mm, and almost same as the observed one. As shown in Fig.14 (b), the major slug characteristic behavior observed in the experiment was reproduced in the numerical simulation by TPFIT code.

The measured and calculated differential pressure and cross flow rate between Ch.1 and Ch.2 for steam-water flow are shown in Figs.15 and 16 respectively. The calculated values of the differential pressure and the cross flow rate agreed well with the measured values.

Inlet mass flow rate (kg/s) Inlet quality (%) Ch.1 Ch.2 Ch.1 Ch.2 0.44 0.23 0.0 0.47

Fig. 14. Observed and calculated slug behavior of steam-water fluid mixing test around the

The slug behaviors observed and calculated around the interconnection is shown in Fig.14. As shown in Fig.14 (a), a part of single steam slug in Ch.2 intrudes to the Ch.1 through the interconnection. Averaged slug length is about 56 mm, and observed major slug

Steam intrusion from Ch.2 to Ch.1 is firstly occurred at the upper part of the steam slug

Constriction is generated at the center part of the steam slug by water flow from Ch1 to

As shown in Fig.14 (b), the occurrence of intrusion of steam from the Ch.2 to the Ch.1 can be effectively calculated, and the calculated amount of steam penetration into the interconnection looks quite similar to the observed one. Predicted slug length is about 59 mm, and almost same as the observed one. As shown in Fig.14 (b), the major slug characteristic behavior observed in the experiment was reproduced in the numerical

The measured and calculated differential pressure and cross flow rate between Ch.1 and Ch.2 for steam-water flow are shown in Figs.15 and 16 respectively. The calculated values of the differential pressure and the cross flow rate agreed well with the measured values.

Table 4. Steam-water flow calculation condition.

interconnection.

characteristic behavior is as follows.

Ch.2, and the steam slug break up ("B" in the Fig.14).

("A" in the Fig.14).

simulation by TPFIT code.

Fig. 15. Measured and calculated pressure difference between subchannels.

Fig. 16. Measured and calculated pressure difference between subchannels.
