Development of Multi-Stage Steam Injector for Feedwater Heaters in Simplified Nuclear Power Plant

Abstract

A steam injector (SI) is a simple, compact and passive pump and also acts as a highperformance direct-contact compact heater to heat up feedwater by using extracted steam from the turbine. To develop high performance compact feedwater heater, it is necessary to quantify the characteristics between physical properties of the flow field. Its performance depends on the phenomena of steam condensation onto the water jet surface and heat transfer in the water jet due to turbulence on to the phase-interface. The analysis was conducted by using CFD code embedded separate two-phase flow models that were confirmed by the experimental data. As the four-stage SI is compact heater, the system is expected to bring about great simplification and materials-saving effects, and high reliability of its operation. Therefore, it is confirmed that the simplification of the power plant by replacing all lowpressure feedwater heaters with the four-stage SI system, having steam extraction pressures equal to those for the existing ABWR system.

Analysis of Heat Balance on Innovative-Simplified Nuclear Power Plant Using Multi-Stage Steam Injectors

“…The experiments and computational fluid dynamics (CFD) for multi-stage SI have been carried out and these data were used to check the performance of SI before calculating the plant efficiency with SI (6), (7) . A three stage SIs and a jet-deaerator (DA), which was developed as a steam recirculation loop and functioned as the 4th-stage SI to warm droplets and to separate water and vapor, were installed in an experimental facility.…”

“…5 shows the simulation results of pressure distribution and Fig. 6 shows the simulation results of temperature distribution, as produced by this CFD (7) . In the pressure distribution, the pressure of water and steam are raised up at each SI stage.…”

“…In the temperature distribution, the temperatures of water and steam are raised up at each stage. It is important to improve the performances of the steam injector especially in the first-stage, to enhance the plant thermal efficiency from results of CFD (7) . Because the first-stage SI is worked with the lowest-pressure extracted steam of 0.05 MPa from the low-pressure turbine.…”

“…Performance experiments were carried out with 1/7-scaled and 1/5-scaled tests to confirm the CFD (6), (7) . The steam pipe connected to the first-stage SI has the largest diameter among the three stages.…”

“…The innovative-simplified NPP with high-efficiency SI can achieve high thermal conductivity because water and steam are mixed directly. However, the plant effi- In this study, we explain the observed mechanisms of the SI experimentally and investigate the computational fluid dynamics (CFD) (6), (7) . The SI model for the heat balance simulator of the 1 100 MWe-class BWR has been developed.…”