Flow Network System Research Articles

Comparison and Validation of Models for the Design of Optimal Economic Pipe Diameters: A Case Study in the Anseba Region, Eritrea

An optimal design for a pressurized flow pipe network is characterized by being economical and contributing the least amount of losses during water transmission through the system. The diameter of a pipe in a network system that delivers the desired effect with the minimum amount of waste and expenses is referred to as an optimal pipe size. The Life-Cycle Cost Analysis (LCCA) model is widely recognized as the recommended standard technique to estimate the optimal pipe size for any pipe flow network system. Numerous empirical formulas have been proposed to simplify the computations required in this economic analysis model. This study seeks to compare the various empirical models that have been proposed by different authors based on a variety of physical variables involved in fluid flow dynamics. Eleven different empirical equations were chosen in order to select the optimal diameter for the network at the Hamelmalo Agricultural College farm located in the Anseba region of Eritrea for the distribution of water to the different sub-plots. The estimated diameters were compared to the standard diameter calculated using the standard LCCA method. This comparison was based on the estimated total head losses and economic analysis of the pipe diameters chosen for such network. Moreover, a statistical analysis was conducted to obtain the best-fit recommended modeled diameter for the network. The Bresse’s model performance was the most adequate when compared with the LCCA model.

Design and Development of Water Flow Network using IoT

During the past decades water needs have risen exponentially to an unprecedent- ed scale in India. Due to increase in population, water consumption and water distribution has become critical problem. To triumph over problems related to water supply and for equal distribution of water there is a need for efficient automated device. This paper pro- poses the conceptual design of automated water flow network and distribution system using IoT for highly populated urban areas such as apartments. The system is fully automated with closed loop structure. The heart of proposed design has a microcontroller which ex- tracts and processes the data from electronic flow rate sensors and monitors the flow of wa- ter to each user based on predetermined threshold level. Hence the water is equally distrib- uted among the user according to their needs. IoT provides the information services required for water flow networks.

Simulation model for centrifugal pump in flow networks based on internal characteristics

Abstract For the simulation of centrifugal pump in flow network system, in general three approaches can be used, the fitting model, the numerical method and the internal characteristics model. The fitting model is simple and rapid thus widely used. The numerical method can provide more detailed information in comparison with the fitting model, but increases implementation complexity and computational cost. In real-time simulations of flow networks, to simulate the condition out of the rated condition, especially for the volume flow rate, which the accuracy of fitting model is incredible, a new method for simulating centrifugal pumps was proposed in this research. The method based on the theory head and hydraulic loss in centrifugal pumps, and cavitation is also to be considered. The simulation results are verified with experimental benchmark data from an actual pump. The comparison confirms that the proposed method could fit the flow-head curves well, and the responses of main parameters in dynamic-state operations are consistent with theoretical analyses.

Energy Flow Hybrid Petri Nets Model of Steel Enterprises

As the urgency of current energy-saving and discharge reduction task and difficult of related advance technology in breaking through, a new energy flow network system model was built based on modelling elements and rules of hybrid Petri nets to adapt to the system requirements through analyzing the basis features of energy flow network, and meet the demand of developing energy flow network efficiency of iron and steel enterprises. The dynamic rules and behaviour mechanism of energy flow network system for iron and steel enterprises were studied by utilizing the model combined with the historical data, the results show that the modelling method is effective and satisfactory, and provide guidance for optimizing the energy system and exploring the relation of material flow and energy flow.

Minimization of the Expected Total Net Loss in a Stationary Multistate Flow Network System

In the present paper, a three-component, stationary, multistate flow network system is studied. Detailed costs and incomes are specified. The aim is to minimize the expected total net loss with respect to the expected times the components spend in each state. This represents a novelty in that we connect the expected component times spent in each state to the minimal total net loss of the system, without first finding the component importance. This is of interest in the design phase where one may tune the components to minimize the expected total net loss. Due to the complex nature of the problem, we first study a simplified version. There the expected times spent in each state are assumed equal for each component. Then a modified version of the full model is presented. The optimization in this model is completed in two steps. First the optimization is carried out for a set of pre-chosen fixed expected life cycle lengths. Then the overall minimum is identified by varying these expectations. Both the simplified and the modified optimization problems are nonlinear. The setup used in this article is such that it can easily be modified to represent other flow network systems and cost functions. The challenge lies in the optimization of real life systems.

Branch and Bound Algorithm for Optimal Sensor Network Design

The sensor network design procedure developed by Nabil and Narasimhan (2012), which relates process economics and data reconciliation, involves the formulation of a mixed integer cone program. The solution to this problem yields the globally optimal sensor network. A branch and bound method can be used to find the global optimum; however, for systems with large numbers of variables, this approach may require a large amount of computational effort to find the solution. In this paper, a specialized branch and bound algorithm is proposed for solving the sensor network design problem, which uses certain heuristics to obtain a solution faster. One involves a low rank factorization to reduce the size of the relaxed problem. The other involves an approximation of the global lower bound for the branch and bound solution. The utility of this algorithm is demonstrated on a simple flow network, a small but realistic evaporator system, and a medium sized steam metering network.

The effects of crossflow gap and axial bypass gap distribution on the flow characteristics in prismatic VHTR core

In prismatic VHTR design, the occurrence of the bypass gap between the core blocks is inevitable for installation and refueling. Since the core bypass flow affect both the reactor efficiency and core thermal margin, it is important to evaluate the bypass flow distribution accurately. The gap size varies with the reactor fuel cycle as the dimension of graphite block varies due to the fast-neutron induced shrinkage and thermal expansion. In particular, the dimensional change of graphite block is different from each location in the core, since the neutron fluence of the blocks is different locally. In addition, fuel and reflector blocks are rearranged by axial shuffling for refueling, so that bypass gap distribution is not axially uniform. Therefore, the consideration of axial profile of the bypass gap is important for accurate evaluation of bypass flow but most of the previous studies assumed uniform bypass gap size. In present study, the multi-block air test experiment was carried out to evaluate the bypass flow distribution with the consideration of axially varying bypass gap profile and the crossflow effect. Axial bypass gap profile of 6mm, 2mm, 4mm, 2mm from top to bottom layer and the crossflow gap of 2mm were tested in the experiment. In addition, comparative computational fluid dynamics (CFDs) analysis for the multi-block experiment was carried out to supplement the experimental limit and to analyze the local flow characteristics in detail. The results suggest that the CFD code, CFX-12 has a sufficient capability to analyze the VHTR core and the prismatic VHTR core should be modeled as the flow network system. The experimental data and CFD simulation results could be used to validate the thermal–hydraulics system code for VHTR system.

A Turbulent Transport Network Model in MULTIFLUX Coupled with TOUGH2

A new numerical method is described for the fully iterated, conjugate solution of two discrete submodels, involving (a) a transport network model for heat, moisture, and airflows in a high-permeability, air-filled cavity; and (b) a variably saturated fractured porous medium. The transport network submodel is an integrated-parameter, computational fluid dynamics solver, describing the thermal-hydrologic transport processes in the flow channel system of the cavity with laminar or turbulent flow and convective heat and mass transport, using MULTIFLUX. The porous medium submodel, using TOUGH2, is a solver for the heat and mass transport in the fractured rock mass. The new model solution extends the application fields of TOUGH2 by integrating it with turbulent flow and transport in a discrete flow network system. We present demonstrational results for a nuclear waste repository application at Yucca Mountain with the most realistic model assumptions and input parameters including the geometrical layout of the nuclear spent fuel and waste with variable heat load for the individual containers. The MULTIFLUX and TOUGH2 model elements are fully iterated, applying a programmed reprocessing of the Numerical Transport Code Functionalization model-element in an automated Outside Balance Iteration loop. The natural, convective airflow field and the heat and mass transport in a representative emplacement drift during postclosure are explicitly solved in the new model. The results demonstrate that the direction and magnitude of the air circulation patterns and all transport modes are strongly affected by the heat and moisture transport processes in the surrounding rock, justifying the need for a coupled, fully iterated model solution such as the one presented in the paper.

A new finite volume method on junction coupling and boundary treatment for flow network system analyses

AbstractTo adequately analyze the flow in a pipe or duct network system, traditional node‐based junction coupling methods require junction losses, which are specified by empirical or analytic correlations. In this paper, a new finite volume junction coupling method using a ghost junction cell is developed by considering the interchange of linear momentum as well as the important wall effect at the junction without requiring any correlation on the junction loss. Also, boundary treatment is modified to preserve the stagnation enthalpy across boundaries, such as the pipe end and the interface between the junction and the branch.The computational accuracy and efficiency of Godunov‐type finite volume schemes are investigated by tracing the total mechanical energy of rapid transients due to sudden closure of a valve at the downstream end. Among the approximate Riemann solvers, the proposed RoeM scheme turns out to be more suitable for finite volume junction treatment than the original Roe's approximate Riemann solver because of conservation of the stagnation enthalpy across the geometric discontinuity. From the viewpoint of computational cost, the implicit LU‐SGS time integration is appropriate for steady and slow transients, while the explicit third‐order TVD Runge–Kutta scheme is advantageous for rapid transients. Copyright © 2009 John Wiley & Sons, Ltd.

Development of a flow network simulation program part I — flow analysis

An in-house simulation program was developed that can be utilized to predict flow characteristics such as pressure and velocities in any flow network system comprising multiple flow components, i.e., pipe, pump, heat exchanger, valves, etc. Although the code is intended for applications to network flow systems in a vehicle, it is written in a generalized manner to handle any possible network configuration of flow components. Therefore, it can easily function in various industrial applications. The network system where the flow is assumed to be one-dimensional is mathematically formulated by applying two conservation rules, mass and energy, to each flow component. These rules produce a set of non-linear equations. These non-linear equations are solved iteratively by adopting the Newton-Raphson scheme. This program has been tested in many different cases to demonstrate its validity and applicability. In this paper, two examples are introduced to show how the program can be used to find solutions in real engineering problems. Throughout the study, it was found that the code can most efficiently be used to verify a proposed design concept in an early design stage of the vehicle development cycle. The thermal analysis portion of the program will be dealt with in Part II of the paper.

Building Multivariate Models from Compressed Data

The effect of data compression on multivariate analysis, especially on principal components analysis (PCA) based modeling, is evaluated in this paper. A comparative study between the “swinging door” and “wavelet compression” algorithms is performed in the context of multivariate data analysis. It is demonstrated that wavelet compression preserves the correlation between different variables better than swinging door compression. It is also demonstrated that the impact of compression increases as the dynamics of the processes become faster and more stochastic in nature. Instead of interpolation based reconstruction of swinging-door-compressed data and subsequent modeling, an iterative missing data technique is suggested for building a PCA model from swinging-door-compressed data. The performance of the proposed methodology is demonstrated using a simulated flow-network system and an industrial data set.

Missing Data Treatment Using Iterative PCA and Data Reconciliation

Two methods, one based on Iterative Principal Components Analysis(IPCA) and the other based on Data Reconciliation have been developed for estimating a model from a data matrix containing missing data. These algorithms are iterative in nature and analogous to the method based on PCA for treating missing data. The methods incorporate information about the measurement errors to develop the models and are optimal in a maximum likelihood sense. The close connection of the methods with the Expectation Maximization (EM) algorithm is also established. Simulated data from a Flow Network system with a variety of error structures and missing data is used to evaluate the performance of the proposed methods. In all cases, models estimated by the proposed methods were superior to those obtained by the classical PCA-based missing data treatment algorithms for nonuniform error.

An improved method for flow network design

An improved method is presented for the design of a complex flow network system. The method employs head loss and flow rate in the iteration process for the determination of flow rates and/or pressure drop. This represents a major departure from the conventional approach which uses only the flow rate. The two-step iteration method proposed here drastically improves both the convergence rate and iteration stability. Tests on different examples have shown that, for most design applications, three iterations are sufficient to yield an accurate final solution, regardless of the initial guess.

充填層における気液向流流れのシミュレーション

A mathematical model was presented to describe the countercurrent flows of gas and liquid through packed beds for analyzing flow phenomena in a blast furnace.For the gas flow, the vectorial form of Ergun's equation was used as equation of motion. For the liquid flow in the packed bed, flowing region was obtained by a dispersion-probability model using a flow network system for the dispersed flow. Liquid flow vector in the flowing region was computed from the Darcy's equation that was derived for the continuous liquid flow.A series of experiments was conducted by a two dimensional cold model for measuring the liquid flow region, liquid distribution at the receivers and gas pressure distribution in the packed beds. The experimental data were simulated well by the mathematical model presented in this paper. In addition, the model estimated the dry zone formed in front of gas inlet.

Two new component importance measures for a flow network system

This paper presents two new component importance measures for a flow network system with random arc capacities: 1. (1) system availability improvement potential of the component; 2. (2) expected unutilized capacity of the component. A numerical example is given.