Revisiting Pipe Component Design

Under recent economic pressures to reduce the cost of electricity, the nuclear power industry has explored new ways to reduce costs and increase electricity generation. One overlooked area where lost power output can be recaptured and attendant problems (e.g., flow-induced vibration (FIV)) addressed is the main steam piping system. The technology underlying piping system components is essentially >100 years old, and incentives to improve pipe components have been limited by costs (development, retrofitting and unforeseen risks and problems) and analysis tools that are incapable of assessing candidate designs. More recently, market and technology conditions have changed that provide additional incentives to address these problems. Firstly, power uprates have resulted in higher steam flow speeds that increase head losses and, in some cases, exacerbate fatigue inducing FIV. Secondly, the cost competitiveness of alternative energy sources, and smaller profit margins, have increased the willingness of the industry to squeeze out moderate power generation increases (e.g., 1% via measurement uncertainty recovery) and address FIV and other flow-related problems that increase maintenance costs. Thirdly, the potential of sophisticated computational fluid dynamics (CFD) software has significantly advanced design assessment capabilities. Unfortunately, contemporary CFD methods are difficult and expensive to use, and current approaches to redesign piping components use a combination of experimental testing and limited flow modeling, together with human intuition regarding the geometrical modifications anticipated to improve flow and reduce unsteadiness. What is lacking however is a formal design approach that automates both the analysis process and the design search – exactly what the proposed effort seeks to address. Recently, Continuum Dynamics, Inc. developed a novel prototype CFD solver, denoted CGE, which is both easy to use and generates predictions with industry leading accuracy. The proposed effort builds upon this prototype state-of-the art Cartesian grid-based CFD solver, that eliminates user involvement in the mesh generation process, analysis, and design optimization, to develop a design and analysis system tailored specifically to the needs of the nuclear power industry in assessing and correcting piping system losses and FIV. The Phase I effort saw the initial development of an efficient, easy-to-use CFD software tool for analyzing complicated piping systems and developing of new improved designs. In Phase I, a prototype analysis was developed, and an adjoint-based geometry optimization procedure was formulated and tested. New piping component designs identified in Phase I were non-obvious, and demonstrated significant reductions in head loss and swirl. Phase I established proof-of-concept, and lays the foundation for Phase II that would see the full implementation of the adjoint-based optimization method in the CGE CFD solver, implementation of additional turbulence modelling options, high performance computing scalability enhancements, and integration into a design framework, along with extensive software debugging, validation and testing on real-world problems. A successful effort would produce a robust, validated, and easy-to-operate computational tool for the analysis and geometrical design of fluid transport components that minimize head loss and dynamic structural loads that are important issues for the nuclear power industry. Indeed, addressing such problems, that currently reduce generation capacity and increase maintenance costs through unscheduled outages related to component failure, is critical to ensuring the viability of nuclear power by maintaining cost competitiveness with other sources of electricity. Given the need for such a capability, together with prior experience in addressing internal flow problems in the nuclear industry, CDI believes that with modest market entry, the combined sales, and associated service work, could generate cumulative revenues in excess of $34M in the first ten years of commercialization after Phase II. Cost savings for customers, which would be passed on to the rate paying public, would be at least an order of magnitude larger, and would be attributed to lower maintenance costs, improved power generation, and longer component service life.