An Upwind Numerical Method for a Hyperbolic One-Dimensional Two-Fluid Model

This study discusses on the implementation of an upwind method for a one-dimensional two-fluid model including the surface tension effect in the momentum equations. This model consists of a complete set of six equations including two-mass, two-momentum, and two-internal energy conservation equations having all real eigenvalues. Based on this equation system with upwind numerical method, the present authors first make a pilot code and then solve some benchmark problems to verify whether this model and numerical method is able to properly solve some fundamental one-dimensional two-phase flow problems or not.

Design of a Large Diameter Steel Reinforced Plastic Pipe

A steel reinforced plastic pipe (PSP), which is composed of two layers of high density polyethylene (HDPE) matrix and a high strength steel wire mesh skeleton, has wide applications in many industrial areas, such as gas and petroleum transportation, etc. In order to achieve higher efficency and lower costs, a large diameter PSP has been developed. However, requirements of the large diameter PSP in safety and economy are much higher, compared with those small diameter PSPs, and some potential problems should be taken into account. In this paper, relevant structural parameters of the large diameter PSP are determined, based on a previously proposed model, and a short-term burst test is carried out. The experiment results agree with the theoretical results quite well. Subsequently, the resistance of vertical pressure and uniform external pressure are evaluated by using experiment investigation and finite element method, respectively. And corresponding results indicate the large diameter PSP with determined structural parameters is qualified to use.

RCC-MRx Appendix A16 Methodology for the Analytical J Calculation Under Thermal and Combined Thermal + Mechanical Loadings for Pipes and Elbows and Related Assessment Tool MJSAM

RCC-MRx code provides flaw assessment methodologies and related tools for Nuclear Power Plant cracked components. An important work has been made in particular to develop a large set of compendia for the calculation of the parameter J for various components (plates, pipes, elbows,…) and various defect geometries. Also, CEA in the frame of collaborations with IRSN, developed a methodology for J analytical calculation for cracked pipes and elbows submitted to thermal and combined mechanical and thermal loadings. This paper presents first the development of this methodology and an overview of the validation strategy, based on reference 2D and 3D F.E. calculations. The second part of the paper presents the last version of the MJSAM tools which is based on the 2010 version of the appendix A16 of the RCC-MRx code. All compendia (for KI, J and C* calculation) and all defect assessment procedures have been implemented in the tool: It covers crack initiation and propagation under fatigue, creep, creep-fatigue and ductile tearing situations. Sensitivity and probabilistic analyses can also been performed with this tool, directly linked to Microsoft Excel software for the results exploitation.

Strength Evaluation for Pressure-Containing Parts of Ultra-High-Pressure Compressor by Using Standards of Ultra-High-Pressure Gas Equipment

The Japanese standard “KHK-S-0220” (KHK-code) and the American standard “Boiler and Pressure Vessel Code Sec.8 Div.3” (ASME-code) concerning ultra-high-pressure gas equipment were applied to Hitachi’s ultra-high-pressure compressor, and a series of strength evaluations were carried out. Hitachi produces and maintains ultra-high-pressure reciprocating compressors with a design pressure over 200 MPa. In Japan, ultra-high pressure gas equipment over 100 MPa must be designed according to KHK-code established by the High Pressure Gas Safety Institute of Japan. This Japanese standard was applied to an ultra-high-pressure compressor, and design pressure limits, shakedown limits, required absorbed energy of materials, leak-before-break (LBB), and fatigue strength were evaluated. ASME-code was also applied to the compressor, and strength evaluations like the above were carried out. As a result, it was found that KHK-code and ASME-code gave conservative evaluation of fatigue strength for an ultra-high-pressure compressor.

Estimation of the V-Factor for Circumferentially Cracked Pipes Under Combined Thermal and Mechanical Stresses Using a Strain-Based Failure Assessment Diagram

This paper presents finite element solutions for elastic-plastic J for circumferentially cracked pipes under combined mechanical and thermal loads in terms of the V/Vo factor used within a strain-based failure assessment diagram. In this study, 3-dimensional finite element analyses are conducted to calculate the V-factor under combined mechanical and thermal load. It is found that estimation of V/Vo is sensitive to the method used for its evaluation. For larger thermal stresses, currently proposed estimation methods are overly conservative.

Dynamic Simulation of Piping System Around Safety Valve for Closed Discharge System

Reaction force of safety valves acting to the piping system is one of key factors for the piping system design around the safety valves. In case of open discharge system, it is well known that a large reaction force acts to the piping corresponding to the fluid momentum force at the atmospheric discharge. On the other hand, reaction forces for closed discharge system may be relatively small since the forces acting to the adjacent two points with flow direction change such as elbows and tees are balanced within very short period. However, large reaction forces may act as a result of unsteady flow just after the initial activation of the safety valve. API RP520 mentioned that a complex time history analysis of the piping system around the safety valves may be required to obtain the transient forces. This paper explains a method of a comprehensive dynamic simulation of piping system around safety valves taking interaction among the valve disc motion, the fluid transient for compressible flow and the piping structural dynamics into account. The simulation results have good agreement with the experimental data. The effectiveness of this method is confirmed throughout an application to actual piping system around safety valves.

Prediction of the Absence of Brittle Failure Risk for Ferritic Steel Piping Components in the Brittle-Ductile Region

This paper deals with the brittle fracture risk evaluation for a C-Mn piping component in the upper shelf of the brittle to ductile fracture transition temperature range, with the main objective to validate a predictive criteria, able to demonstrate the complete absence of brittle fracture risk. The criteria is based one a critical stress and the volume around the crack were the maximum principal stress exceed this critical stress. The model is calibrated on notched tensile specimens and CT specimens. A four-points bending pipe test has then been designed using this criterion to insure that no brittle fracture will occurs at a temperature that all CT specimens failed by cleavage. The material is a French secondary loop Tu42C ferritic steel and the pipe dimensions for the test are the same than the size of the principal secondary loop pipes. The results of the pipe test confirm the prediction with the model and the interpretation lead to define an equivalence between the loading conditions (based on the J parameter) of the pipe and the loading condition of a CT specimen.

Thermal Hydraulic Studies on Helical Coil Steam Generator by CFD

NuScale Power, Inc. is commercializing a 45 Megawatt electric light water nuclear reactor NuScale Power Module (NPM). Each NPM includes a containment vessel, a reactor vessel, a nuclear reactor core, an integral steam generator, and an integral pressurizer. The NuScale Power Module is cooled by natural circulation. The primary coolant in the Reactor Pressure Vessel is heated in the nuclear core, it rises through a central riser, it spills over and encounters the helical coil steam generator, it is cooled as steam is generated inside the steam generator, and it is again heated in the nuclear core. The Steam Generator also must be designed to provide adequate heat transfer, to allow adequate primary reactor coolant flow, and to provide adequate steam flow to produce the required power output. This paper presents the CFD results that describe the transport phenomena on the heat transfer and fluid flow dynamics in helical coil steam generator tubes. The ultimate goal of the CFD modeling is to predict the steam outlet conditions associated with the chosen helical coil tube geometries, solving the primary and secondary flow region together coupled with the helical coil tube. However, current studies are focused on the primary side with the heat flux boundary condition assigned on the outer surface of the helical coil steam generator. In this study, the ANSYS CFX v. 12.1 [1] was used to solve the three-dimensional mass, momentum and energy equations. The helical coil steam generator has complex geometry and modeling entire geometry requires the enormous memory that is beyond our hardware capability and is not practical. Therefore, geometry was limited to 1 degree of the wedge and 5% of the total length in the middle. Only external flow, single phase flow around the helical coils, is simulated using the standard k-ε model and shear stress transport model. From the results of the numerical simulation, the pressure drop and temperature profiles were determined. It is important to understand thermal hydraulic phenomena for the design and performance prediction of the reactor internal.

Comparative Assessment of Turbulence Models for Prediction of Flow-Induced Corrosion Damages

The present study makes a comparative assessment of different turbulence models in simulating the flow-assisted corrosion (FAC) process for pipes with noncircular cross sections and bends, features regularly encountered in heat exchangers and other pipeline networks. The case study investigates material damage due to corrosion caused by dissolved oxygen (O2) in a stainless steel pipe carrying an aqueous solution. A discrete solid phase is also present in the solution, but the transport of the solid particles is not explicitly modeled. It is assumed that the volume fraction of the solid phase is low, so it does not affect the continuous phase. Traditional two-equation models are compared, such as isotropic eddy viscosity, standard k-ε and k-ω models, shear stress transport (SST) k-ω models, and the anisotropic Reynolds Stress Model (RSM). Computed axial and radial velocities, and turbulent kinetic energy profiles predicted by the turbulence models are compared with available experimental data. Results show that all the turbulence models provide comparable results, though the RSM model provided better predictions in certain locations. The convective and diffusive motion of dissolved O2 is calculated by solving the species transport equations. The study assumes that solid particle impingement on the pipe wall will completely remove the protective film formed by corrosion products. It is also assumed that the rate of corrosion is controlled by diffusion of O2 through the mass transfer boundary layer. Based on these assumptions, corrosion rate is calculated at the internal pipe walls. Results indicate that the predicted O2 corrosion rate along the walls varies for different turbulence models but show the same general trend and pattern.

Anti-Seize, Friend or Foe, the Properties That Really Matter!

There is a lot of misinformation published about anti-seize compounds around friction (or K factors) factors and temperature limits. Anti-seize materials exist to serve two functions, to help even out stud stresses/preloads during assembly, and most importantly, allow the components to be taken apart after they have been exposed to heat. This paper looks at how different anti-seize materials are affected after being exposed to enough heat to burn off the grease base.