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ABSTRACT
In the design process of a steam generator, a porous-media-approach computational code is utilized for simulating three-dimensional two-phase flow behavior in the secondary side of steam generators. For the design of next-generation steam generators, the advanced thermal-hydraulic analysis code based on the two-fluid model has been developed by implementing constitutive equations into the ANSYS fluent. For code validation, experiments using two-phase simulant fluids were performed to collect data in a simulated steam generator with a triangular tube array. The simulant two-phase flow system selected in the experiment was an adiabatic sulfur hexafluoride gas and liquid ethanol system, which allowed us to achieve the density ratio of prototypic steam-water flow with low pressure (=0.68 MPa). In the experiment, void fraction and gas–liquid interfacial velocity distributions along U-tubes were measured. The code validation was conducted by analyzing code predictions for measured distributions of void fraction and interfacial velocity under prototypic full load and partial load conditions, i.e., 50–80% flow rate conditions. Their bias and random errors were evaluated. The reasonable random errors demonstrated the validity of the newly developed code based on the two-fluid model in terms of predictions of void fraction and interfacial velocity in the secondary side of steam generators.
Nomenclature
| A | = | structural surface area |
| = | interfacial area concentration | |
| = | parameter | |
| = | constant (=1.7) | |
| = | drag coefficient acting on gas phase | |
| = | drag coefficient for cross-flow | |
| = | covariance | |
| = | hydraulic equivalent diameter | |
| = | rod diameter | |
| = | volume porosity | |
| = | external force per unit volume acting on two-phase flow | |
| = | two-phase mixture mass flux in i-th injection unit | |
| = | two-phase mixture mass flux in riser section | |
| = | friction factor | |
| = | gravitational acceleration | |
| = | unit tensor | |
| = | mixture volumetric flux | |
| = | generalized interfacial drag force per unit volume | |
| = | interfacial drag force per unit volume | |
| = | number of tube row | |
| = | smallest rod pitch | |
| = | pressure | |
| = | quantity | |
| = | time | |
| = | free volume in a control volume | |
| = | total control volume | |
| = | velocity | |
| = | interfacial velocity at the center of equilateral-triangle rod pattern | |
| = | relative velocity |
Greek symbol
| = | void fraction | |
| = | critical void fraction | |
| = | volumetric flow fraction | |
| = | mass generation rate | |
| = | azimuthal distance | |
| = | pressure drop due to form drag for two-phase cross-flow over horizontal heat transfer tubes | |
| = | pressure drop due to wall friction for two-phase parallel flow along with vertical heat transfer tubes | |
| = | density difference between gas and liquid phases | |
| = | density | |
| = | surface tension | |
| = | viscous stress | |
| = | turbulent stress | |
| = | two-phase multiplier by Chisholm’s correlation | |
| = | two-phase multiplier by Thom’s correlation | |
| = | variable | |
| = | angle |
Subscripts
| = | liquid | |
| = | gap | |
| = | gas | |
| = | k-phase | |
| = | mixture | |
| = | -direction | |
| = | sub-channel | |
| = | -direction | |
| = | -direction | |
| = | -direction | |
| = | approaching velocity |
Mathematical operators
| = | intrinsic phase average quantity | |
| = | void-fraction-weighted-mean quantity | |
| = | phase average quantity | |
| = | phase density-weighted mean quantity |
Acknowledgments
The experimental and validation works in this study have been carried out as a Japanese government-subsidized R & D project, “The Safety Improvement of Nuclear Facilities,” with the participation of the Kansai Electric Power Co., Inc., Hokkaido Electric Power Co., Inc., Shikoku Electric Power Co., Inc., Kyushu Electric Power Co., Inc., The Japan Atomic Power Company, The Institute of Applied Energy, and Mitsubishi Heavy Industries, Ltd.
Disclosure statement
No potential conflict of interest was reported by the author(s).