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Book part
Publication date: 18 July 2016

Daniel E. O’Leary

Los Angeles, California, is facing record drought conditions. As a result, there is interest in all things related to building and maintaining water capabilities. Leaks in…

Abstract

Los Angeles, California, is facing record drought conditions. As a result, there is interest in all things related to building and maintaining water capabilities. Leaks in the infrastructure can lead to costly losses of water resources. Accordingly, attention increasingly is being devoted to water leak management. Using data available through the City of Los Angeles’ open data movement, the number of leaks is analyzed in order to study both the impact of temperature and whether the number of leaks is decreasing over time. Three different approaches for modeling the number of leaks, including regression, time series, and neural networks, are compared.

Details

Advances in Business and Management Forecasting
Type: Book
ISBN: 978-1-78635-534-8

Keywords

Abstract

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Radical Transparency and Digital Democracy
Type: Book
ISBN: 978-1-80043-763-0

Abstract

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Radical Transparency and Digital Democracy
Type: Book
ISBN: 978-1-80043-763-0

Article
Publication date: 28 September 2018

Jyothiprakash K.H., Krishnegowda Y.T., Krishna Venkataram and K.N. Seetharamu

Heat exchangers working in cryogenic temperature ranges are strongly affected by heat ingression from the ambient. This paper aims to investigate the effect of ambient…

Abstract

Purpose

Heat exchangers working in cryogenic temperature ranges are strongly affected by heat ingression from the ambient. This paper aims to investigate the effect of ambient heat-in-leak on the performance of a three-fluid cross-flow cryogenic heat exchanger.

Design/methodology/approach

The governing equations are derived for a three-fluid cross-flow cryogenic heat exchanger based on the conservation of energy principle. For given fluid inlet temperatures, the governing equations are solved using the finite element method to obtain exit temperatures of the three-fluid exchanger. The performance of the heat exchanger is determined using effectiveness-number of transfer units (e-NTU) method. In the present analysis, the amount of ambient heat-in-leak to the heat exchanger is accounted by two parameters Ht and Hb. The variation of the heat exchanger effectiveness due to ambient heat-in-leak is analyzed for various non-dimensional parameters defined to study the heat exchanger performance.

Findings

The effect of ambient heat in leak to the heat exchanger from the surrounding is to increase the dimensionless exit mean temperature of all three fluids. An increase in heat in leak parameter (Ht = Hb) value from 0 to 0.1 reduces hot fluid effectiveness by 32 per cent for an NTU value of 10.

Originality Value

The effect of heat-in-leak on a three-fluid cross-flow cryogenic heat exchanger is significant, but so far, no investigations are carried out. The results establish the efficacy of the method and throw light on important considerations involved in the design of such heat exchangers.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 9
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 12 March 2018

Sepideh Yazdekhasti, Kalyan Ram Piratla, John C. Matthews, Abdul Khan and Sez Atamturktur

There has been a sustained interest over the past couple of decades in developing sophisticated leak detection techniques (LDTs) that are economical and reliable. Majority…

Abstract

Purpose

There has been a sustained interest over the past couple of decades in developing sophisticated leak detection techniques (LDTs) that are economical and reliable. Majority of current commercial LDTs are acoustics based and they are not equally suitable to all pipe materials and sizes. There is also limited knowledge on the comparative merits of such acoustics-based leak detection techniques (ALDTs). The purpose of this paper is to review six commercial ALDTs based on four decisive criteria and subsequently develop guidance for the optimal selection of an ALDT.

Design/methodology/approach

Numerous publications and field demonstration reports are reviewed for evaluating the performance of various ALDTs in this study to inform their optimal selection using an integrated multi-criteria decision analysis (MCDA) framework. The findings are validated using interviews of water utility experts.

Findings

The study approach and the findings will have a broad impact on the water utility industry by identifying a suite of suitable ALDTs for a range of typical application scenarios. The evaluated ALDTs include listening devices, noise loggers, leak-noise correlators, free-swimming acoustic, tethered acoustic, and acoustic emissions. The evaluation criteria include cost, reliability, access requirements, and the ability to quantify leakage severity. The guidance presented in this paper will support efficient decision making in water utility management to minimize pipeline leakage.

Originality/value

This study attempts to address the problem of severe dearth of performance data for pipeline inspection techniques. Performance data reported in the published literature on various ALDTs are appropriately aggregated and compared using a MCDA, while the uncertainty in performance data is addressed using the Monte Carlo simulation approach.

Details

Management of Environmental Quality: An International Journal, vol. 29 no. 2
Type: Research Article
ISSN: 1477-7835

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Article
Publication date: 5 October 2020

Ji Wang, Yuting Yan and Junming Li

Natural gas leak from underground pipelines could lead to serious damage and global warming, whose spreading in soil should be systematically investigated. This paper aims…

Abstract

Purpose

Natural gas leak from underground pipelines could lead to serious damage and global warming, whose spreading in soil should be systematically investigated. This paper aims to propose a three-dimensional numerical model to analyze the methane–air transportation in soil. The results could help understand the diffusion process of natural gas in soil, which is essential for locating leak source and reducing damage after leak accident.

Design/methodology/approach

A numerical model using finite element method is proposed to simulate the methane spreading process in porous media after leaking from an underground pipe. Physical models, including fluids transportation in porous media, water evaporation and heat transfer, are taken into account. The numerical results are compared with experimental data to validate the reliability of the simulation model. The effects of methane leaking direction, non-uniform soil porosity, leaking pressure and convective mass transfer coefficient on ground surface are analyzed.

Findings

The methane mole fraction distribution in soil is significantly affected by the leaking direction. Horizontally and vertically non-uniform soil porosity has a stronger effect. Increasing leaking pressure causes increasing methane mole flux and flow rate on the ground surface.

Originality/value

Most existing gas diffusion models in porous media are for one- or two-dimensional simulation, which is not enough for predicting three-dimensional diffusion process after natural gas leak in soil. The heat transfer between gas and soil was also neglected by most researchers, which is very important for predicting the gas-spreading process affected by the soil moisture variation because of water evaporation. In this paper, a three-dimensional numerical model is proposed to further analyze the methane–air transportation in soil using finite element method, with the presence of water evaporation and heat transfer in soil.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 July 2006

Osama Hunaidi and Alex Wang

To introduce a new, low‐cost and easy‐to‐use leak detection system to help water utilities improve their effectiveness in locating leaks. The paper also presents an…

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Abstract

Purpose

To introduce a new, low‐cost and easy‐to‐use leak detection system to help water utilities improve their effectiveness in locating leaks. The paper also presents an overview of leakage management strategies including acoustic and other leak detection techniques.

Design/methodology/approach

The design approach was based on the use personal computers as a platform and enhanced signal processing algorithms. This eliminated the need for a major component of the usual hardware of leak pinpointing correlators which reduced the system's cost; made it easy to use, and improved the effectiveness of locating leaks in all types of pipes.

Findings

Effectiveness of the new leak detection system for pinpointing leaks was demonstrated using real world examples. The system has promising potential for all water utilities, including small and medium‐sized ones and utilities in developing countries.

Practical implications

The leak detection system presented in the paper will help all water utilities, including small and medium‐sized ones and utilities in developing countries, to save water by dramatically improving their effectiveness in locating leaks in all types of pipes.

Originality/value

The paper presents information about a new effective system for locating leaks in water distribution pipes. Effective leak detection tools are needed by water utilities worldwide.

Details

Management of Environmental Quality: An International Journal, vol. 17 no. 4
Type: Research Article
ISSN: 1477-7835

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Article
Publication date: 1 March 2007

Tomohiro Yokozeki

Gas permeability through damage networks in composite laminates is the key issue for the applicability of high‐performance composites to the cryogenic propellant tanks of…

Abstract

Gas permeability through damage networks in composite laminates is the key issue for the applicability of high‐performance composites to the cryogenic propellant tanks of space launch vehicles. A simple model for the gas permeability induced by multilayer matrix cracks in composite laminates is proposed based on the leak conductance at crack intersections, which is an extension of the model by Kumazawa et al (AIAA J. 41, 2037‐ ‐2044, 2003). Experimental evidence on the gas permeability mechanisms is summarized and reflected in the present model. In order to include the effects of applied loadings and damage sizes on the gas permeability, the leak conductance is assumed to be a function of the average crack opening displacements of the matrix cracks and the crack intersection angles. The leak conductance factor was empirically obtained as a function of the crack intersection angle, and the comparison of the gas permeability between the predictions based on the developed model and the experimental results is presented for the validity of this model.

Details

Multidiscipline Modeling in Materials and Structures, vol. 3 no. 3
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 18 December 2020

Piotr Jan Bielawski

The lack of integrity of the piston machine combustion chamber manifests itself in leakages of the working fluid between the piston and the cylinder liner, at valves…

Abstract

Purpose

The lack of integrity of the piston machine combustion chamber manifests itself in leakages of the working fluid between the piston and the cylinder liner, at valves mounted in the cylinder head and between the head and the liner. An untight combustion chamber leads to decreased power output or efficiency of the engine, while leaks of a fluid may cause damage to many components of the chamber. The actual value of working chamber leak is a desired and essential piece of information for planning operations of a given machine.

Design/methodology/approach

This research paper describes causes and mechanisms of leakage from the working chamber of internal combustion engines. Besides, the paper outlines presently used methods and means of leak identification and states that their further development and improvements are needed. New methods and their applicability are presented.

Findings

The methods of leak identification have been divided into diagnostic and non-working machine leak identification methods. The need has been justified for the identification of leakage from the combustion chamber of a non-working machine and for using the leakage measure as the value of the cross-sectional area of the equivalent leak, defined as the sum of cross-section areas of all leaking paths. The analysis of possible developments of tightness assessment methods referring to the combustion chamber of a non-working machine consisted in modelling subsequent combustion chamber leaks as gas-filled tank leak, leak from another element of gas-filled tank and as a regulator of gas flow through a nozzle.

Originality/value

A measurement system was built allowing the measurement of pressure drop in a tank with the connected engine combustion chamber, which indicated the usefulness of the system for leakage measurement in units as defined in applicable standards. A pneumatic sensor was built for measuring the cross-sectional area of the equivalent leak of the combustion chamber connected to the sensor where the chamber functioned as a regulator of gas flow through the sensor nozzle. It has been shown that the sensor can be calibrated by means of reference leaks implemented as nozzles of specific diameters and lengths. The schematic diagram of a system for measuring the combustion chamber leakage and a diagram of a sensor for measuring the cross-sectional area of the equivalent leak of the combustion chamber leakage are presented. The results are given of tightness tests of a small one-cylinder combustion engine conducted by means of the set up measurement system and a pre-prototype pneumatic sensor. The two solutions proved to be practically useful.

Details

Journal of Quality in Maintenance Engineering, vol. 28 no. 1
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 11 September 2009

Suzanne Millar and Marc Desmulliez

The purpose of this paper is to review traditional hermeticity test methods when applied to typical micro‐electro‐mechanical systems (MEMS) cavity volumes and to propose…

Abstract

Purpose

The purpose of this paper is to review traditional hermeticity test methods when applied to typical micro‐electro‐mechanical systems (MEMS) cavity volumes and to propose potential solutions.

Design/methodology/approach

Standards for traditional testing have been applied to typical MEMS cavity volumes and the resulting issues of range and sensitivity discussed. In situ test structures have been designed and fabricated with access to the internal cavities to allow characterisation of the structures as a function of pressure.

Findings

The ultra low leak rates necessary to guarantee hermeticity of MEMS cannot be measured using traditional methods. Optical test methods are possible although in situ test structures currently provide the greatest sensitivity. A portfolio of test techniques is required to allow accurate hermeticity testing of MEMS.

Research limitations/implications

This paper provides a starting point for further investigation into several methods of MEMS hermeticity testing.

Originality/value

This paper provides a review of the limitations of traditional testing and proposals for future testing as the trend towards smaller volume packaging continues.

Details

Sensor Review, vol. 29 no. 4
Type: Research Article
ISSN: 0260-2288

Keywords

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