The Experts below are selected from a list of 30 Experts worldwide ranked by ideXlab platform

Clovis De Arruda Martins - One of the best experts on this subject based on the ideXlab platform.

  • flexible Pipes influence of the pressure armor in the wet collapse Resistance
    Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 2014
    Co-Authors: Clovis De Arruda Martins
    Abstract:

    When submitted to high external pressure, flexible Pipes may collapse. If the external sheath is damaged, all the external pressure is directly applied on the internal polymeric layer that transmits the loading to the carcass layer, which can fail due to this effect, leading to wet collapse. This failure mode must be taken into account in a flexible Pipe design. A model can be set up neglecting the influence of the pressure armor, but this assumption may underestimate the wet collapse pressure value. This work aims to include the pressure armor effect in the numerical prediction of wet collapse. The main contribution of the pressure armor to the flexible Pipe Resistance to collapse is to be a constraint to the radial displacement of the carcass and the internal polymeric layers. Two models were developed to find the wet collapse pressure in flexible Pipes. A first study was done using a ring approximation three-dimensional (3D) finite element method (FEM) model. Comparisons are made with more simplified models using a 3D FEM equivalent ring approximation. The aim is to clarify the mechanical behavior of the pressure armor in the wet collapse scenario. Parametric studies of initial ovalization of carcass and initial gaps and interference between polymeric layer and pressure armor are made and discussed.

  • flexible Pipes influence of the pressure armor in the wet collapse Resistance
    ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering, 2011
    Co-Authors: Clovis De Arruda Martins
    Abstract:

    When subjected to large valued external pressures, flexible Pipes may collapse. If the external sheath is damaged, all the external pressure is directly applied to the internal polymeric layer that transmits the loading to the carcass layer. When the carcass layer fails due to this effect, the wet collapse occurs. This failure mode must be taken into account in the flexible Pipe design. The study for this problem can be done neglecting the influence of the pressure armor, but this assumption may underestimate the wet collapse pressure value. This work aims to study the pressure armor effect in the numerical prediction of wet collapse. The main contribution of the pressure armor to the flexible Pipe Resistance to collapse is to be a constraint to the radial displacement of the carcass and the internal polymeric layers. Two models were developed and compared with the purpose of calculating the critical value of the external pressure that causes carcass layer to collapse. The first and most complete study is done using a ring 3D FEM model that takes into account both the real pressure armor and carcass real profiles. In the second model, the pressure armor is considered adopting an equivalent ring simplification. The comparison of the results of both the models clarifies how the behavior of the pressure armor in the wet collapse situation is. Parametric studies of initial ovalization of the carcass and initial gaps in manufacturing of flexible Pipes are made and discussed.Copyright © 2011 by ASME

Xinmin Lai - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the flow distribution for thin stamped bipolar plates with tapered channel shape
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Linfa Peng, Xinmin Lai
    Abstract:

    Abstract Thin stamped bipolar plate (BPP) is promising for proton exchange membrane fuel cell (PEMFC). However, design laws in conventional method based on graphite BPP are not suitable for the design of stamped BPP since the tapered channel shape influences the flow distribution. By considering the channel cross-section on the stamped BPP, a formula for the Pipe Resistance is proposed to describe the flow Resistance characteristics by introducing a shape factor. The shape factor is calculated by the computational fluid dynamics (CFD) simulation. Then, a theoretical flow network model based on mass and momentum conservation is developed to predict the flow distribution in Z-type flow field configuration. The accuracy of the model has been verified by comparing with CFD results. It is found that the aspect ratio and the base angle have significant influences on the Resistance characteristic and flow distribution. And the results indicate that the homogeneity can be improved by increasing the proportion of flow Resistance in the side channel. The flow network model provides an easy-to-use method to calculate the flow distribution and the results can be used as guidance for the design and optimization of the flow field for stamped BPP.

Caren Tischendorf - One of the best experts on this subject based on the ideXlab platform.

  • steady state behavior of large water distribution systems algebraic multigrid method for the fast solution of the linear step
    Journal of Water Resources Planning and Management, 2012
    Co-Authors: Aaron C Zecchin, P Thum, Angus R Simpson, Caren Tischendorf
    Abstract:

    AbstractThe Newton-based global gradient algorithm (GGA) (also known as the Todini and Pilati method) is a widely used method for computing the steady-state solution of the hydraulic variables within a water distribution system (WDS). The Newton-based computation involves solving a linear system of equations arising from the Jacobian of the WDS equations. This step is the most computationally expensive process within the GGA, particularly for large networks involving up to O(105) variables. An increasingly popular solver for large linear systems of the M-matrix class is the algebraic multigrid (AMG) method, a hierarchical-based method that uses a sequence of smaller dimensional systems to approximate the original system. This paper studies the application of AMG to the steady-state solution of WDSs through its incorporation as the linear solver within the GGA. The form of the Jacobian within the GGA is proved to be an M-matrix (under specific criteria on the Pipe Resistance functions), and thus able to be...

Ping Cheng - One of the best experts on this subject based on the ideXlab platform.

  • design trade offs among shunt current pumping loss and compactness in the piping system of a multi stack vanadium flow battery
    Journal of Power Sources, 2015
    Co-Authors: Ping Cheng
    Abstract:

    Abstract Trade-off between shunt current loss and pumping loss is a major challenge in the design of the electrolyte piping network in a flow battery system. It is generally recognized that longer and thinner ducts are beneficial to reduce shunt current but detrimental to minimize pumping power. Base on the developed analog circuit model and the flow network model, we make case studies of multi-stack vanadium flow battery piping systems and demonstrate that both shunt current and electrolyte flow Resistance can be simultaneously minimized by using longer and thicker ducts in the piping network. However, extremely long and/or thick ducts lead to a bulky system and may be prohibited by the stack structure. Accordingly, the intrinsic design trade-off is between system efficiency and compactness. Since multi-stack configurations bring both flexibility and complexity to the design process, we perform systematic comparisons among representative piping system designs to illustrate the complicated trade-offs among numerous parameters including stack number, intra-stack channel Resistance and inter-stack Pipe Resistance. As the final design depends on various technical and economical requirements, this paper aims to provide guidelines rather than solutions for designers to locate the optimal trade-off points according to their specific cases.

Linfa Peng - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the flow distribution for thin stamped bipolar plates with tapered channel shape
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Linfa Peng, Xinmin Lai
    Abstract:

    Abstract Thin stamped bipolar plate (BPP) is promising for proton exchange membrane fuel cell (PEMFC). However, design laws in conventional method based on graphite BPP are not suitable for the design of stamped BPP since the tapered channel shape influences the flow distribution. By considering the channel cross-section on the stamped BPP, a formula for the Pipe Resistance is proposed to describe the flow Resistance characteristics by introducing a shape factor. The shape factor is calculated by the computational fluid dynamics (CFD) simulation. Then, a theoretical flow network model based on mass and momentum conservation is developed to predict the flow distribution in Z-type flow field configuration. The accuracy of the model has been verified by comparing with CFD results. It is found that the aspect ratio and the base angle have significant influences on the Resistance characteristic and flow distribution. And the results indicate that the homogeneity can be improved by increasing the proportion of flow Resistance in the side channel. The flow network model provides an easy-to-use method to calculate the flow distribution and the results can be used as guidance for the design and optimization of the flow field for stamped BPP.