Optimization of Conical Micro-Diffusers and Micro-Nozzles Considering Entropy Generation

Fluid flow characteristics and entropy generation in a circular diffuser/nozzle element are studied numerically. The flow is assumed to be isothermal, laminar and incompressible with constant thermo-physical properties. The velocity field, mass flow rate, and entropy generation are investigated for several half angles in combination with several values of pressure drops. The effect of diffuser half angle on the entropy generation is investigated and discussed. Furthermore, the effect of the half angle of diffuser on the diffuser efficiency and the effect on the rectification efficiency are explained. It is shown that there is an optimum operation half angle for which the diffuser efficiency has a maximum value. In the case of a micro-diffuser 1 mm long with an inlet diameter of 100 μm, the optimum half angle was found to be 2.5°. These results are based on several parametric simulations ranging from 0 to 7° half angles and covering pressure drops between 500 and 2000 Pa.King Fahd University of Petroleum and Minerals (Deanship of Scientific Research

Design of a Novel In-Pipe Reliable Leak Detector

Leakage is the major factor for unaccounted losses in every pipe network around the world (oil, gas, or water). In most cases, the deleterious effects associated with the occurrence of leaks may present serious economical and health problems. Therefore, leaks must be quickly detected, located, and repaired. Unfortunately, most state-of-the-art leak detection systems have limited applicability, are neither reliable nor robust, while others depend on the user experience. In this paper, we present a new in-pipe leak detection system. It performs autonomous leak detection in pipes and, thus, eliminates the need for the user experience. This paper focuses on the detection module and its main characteristics. Detection in based on the presence of a pressure gradient in the neighborhood of the leak. Moreover, the proposed detector can sense leaks at any angle around the circumference of the pipe with only two sensors. We validate the concepts by building a prototype and evaluate the system’s performance under real conditions in an experimental laboratory setup.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R7-DMN-08)Alexander S. Onassis Public Benefit Foundatio

Analysis and Design of an In-Pipe System for Water Leak Detection

In most cases the deleterious effects associated with the occurrence of leaks may present serious problems and therefore, leaks must be quickly detected, located and repaired. The problem of leakage becomes even more serious when it is concerned with the vital supply of fresh water to the community. In addition to waste of resources, contaminants may infiltrate into the water supply. The possibility of environmental health disasters due to delay in detection of water pipeline leaks has spurred research into the development of methods for pipeline leak and contamination detection. Leaking in water networks has been a very significant problem worldwide, especially in developing countries, where water is sparse. Many different techniques have been developed to detect leaks, either from the inside or from the outside of the pipe; each one of them with their advantages, complexities but also limitations. To overcome those limitations we focus our work on the development of an in-pipe-floating sensor. The present paper discusses the design considerations of a novel autonomous system for in-pipe water leak detection. The system is carefully designed to be minimally invasive to the flow within the pipe and thus not to affect the delicate leak signal. One of its characteristics is the controllable motion inside the pipe. The system is capable of pinpointing leaks in pipes while operating in real network conditions, i.e. pressurized pipes and high water flow rates, which are major challenges.Center for Clean Water for Clean Energy at MIT & KFUP

Design and Evaluation of an In-Pipe Leak Detection Sensing Technique Based on Force Transduction

Leakage is the major factor for unaccounted fluid losses in almost every pipe network. In most cases the deleterious effects associated with the occurrence of leaks may present serious economical and health problems and therefore, leaks must be quickly detected, located and repaired. The problem of leakage becomes even more serious when it is concerned with the vital supply of fresh water to the community. Leaking water pipelines can develop large health threats to people mostly because of the infiltration of contaminants into the water network. Such possibilities of environmental health disasters have spurred research into the development of methods for pipeline leakage detection. Most state of the art leak detection techniques have limited applicability, while some of them are not reliable enough and sometimes depend on user experience. Our goal in this work is to design and develop a reliable leak detection sensing system. The proposed technology utilizes the highly localized pressure gradient in the vicinity of a small opening due to leakage in a pressurized pipeline. In this paper we study this local phenomenon in detail and try to understand it with the help of numerical simulations in leaking pipelines (CFD studies). Finally a new system for leak detection is presented. The proposed system is designed in order to reduce the number of sensing elements required for detection. The main concept and detailed design are laid out. A prototype is fabricated and presented as a proof of concept. The prototype is tested in a simple experimental setup with artificial leakages for experimental evaluation. The sensing technique discussed in this work can be deployed in water, oil and gas pipelines without significant changes in the design, since the concepts remain the same in all cases.King Fahd University of Petroleum and Minerals (Project Number R7-DMN-08

Characterization of In-Pipe Acoustic Wave for Water Leak Detection

This paper presents experimental observations on the characteristics of the acoustic signal propagation and attenuation inside water-filled pipes. An acoustic source (exciter) is mounted on the internal pipe wall, at a fixed location, and produces a tonal sound to simulate a leak noise with controlled frequency and amplitude, under different flow conditions. A hydrophone is aligned with the pipe centerline and can be re-positioned to capture the acoustic signal at different locations. Results showed that the wave attenuation depends on the source frequency and the line pressure. High frequency signals get attenuated more with increasing distance from the source. The optimum location to place the hydrophone for capturing the acoustic signal is not at the vicinity of source location. The optimum location also depends on the frequency and line pressure. It was also observed that the attenuation of the acoustic waves is higher in more flexible pipes like PVC ones.Center for Clean Water and Clean Energy at MIT and KFUP

Reliable Sensing of Leaks in Pipelines

Leakage is the major factor for unaccounted losses in every pipe network around the world (oil, gas or water). In most cases the deleterious effects associated with the occurrence of leaks may present serious economical and health problems. Therefore, leaks must be quickly detected, located and repaired. Unfortunately, most state of the art leak detection systems have limited applicability, are neither reliable nor robust, while others depend on user experience. In this work we present a new in-pipe leak detection system, PipeGuard. PipeGuard performs autonomous leak detection in pipes and, thus, eliminates the need for user experience. This paper focuses on the detection module and its main characteristics. Detection in based on the presence of a pressure gradient in the neighborhood of the leak. Moreover, the proposed detector can sense leaks at any angle around the circumference of the pipe with only two sensors. We have validated the concepts by building a prototype and evaluated its performance under real conditions in an experimental laboratory setup.Alexander S. Onassis Public Benefit Foundatio

Characteristics of air and oxy-fuel combustion in micro-channels

With the fast development of MEMS (micro electro mechanical systems) devices the demand for miniaturized power source is increasing quickly. A micro-combustor is one of the key components of these devices in which the fuel-air mixture is burnt. In the past few years, intense research efforts have been made on catalytic micro-reactors using hydrocarbons as fuel for a variety of portable power production systems. The applications of these micro-reactors include scaled-down thermal engines, wherein a catalytic micro-burner is used for the direct conversion of chemical energy to thermal energy, catalytic micro-thrusters for space applications, and micro-reactors used for fuel reforming in micro solid oxide fuel cells. The present work is aimed at developing Computational Fluid Dynamics (CFD) approach for the investigation of characteristics of air and oxy-fuel combustion in micro-channels. The simulations are based on the numerical solution of the conservation of mass, momentum, energy and species equations of two dimensional flows. The present work as being related to micro-channels will provide a basis for development of new technologies such as carbon-free combustors for use in gas turbines and boilers in order to reduce carbon dioxide emissions.Paper presented to the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.dc201

Determination of important flow characteristics for leak detection in water pipelines-networks

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.The accuracy of a leak detection method depends greatly on the flow and leak parameters in a given pipeline. This paper gives some insight into the flow characteristics around simulated small leaks. The present computational fluid dynamics studies have indicated clear distinctive features in fluid pressure and fluid acceleration that can be used for the early detection of small leaks with the magnitude of 2.75L/min in water distribution pipelines. The CFD study is based on the steady state turbulent flow simulation which was carried out for different pressure lines in 4-inch (100m) ID pipe. Based on the CFD simulation, it was found out that the pressure gradient in the vicinity of the leaks are quite large, hence a leak detection method based on pressure gradient measurement is proposed. In addition these simulation has shown axial flow acceleration in the flow centerline of the pipe have remarkable gradient which offers another leak detection method based on the use of accelerometer.dc201

Quantifying Acoustic and Pressure Sensing for In-Pipe Leak Detection

Experiments were carried out to study the effectiveness of using inside-pipe measurements for leak detection in plastic pipes. Acoustic and pressure signals due to simulated leaks, opened to air, are measured and studied for designing a detection system to be deployed inside water networks of 100 mm (4 inch) pipe size. Results showed that leaks as small as 2 l/min can be detected using both hydrophone and dynamic pressure transducer under low pipe flow rates. The ratio between pipe flow rate and leak flow rate seems to be more important than the absolute value of leak flow. Increasing this ratio resulted in diminishing and low frequency leak signals. Sensor location and directionality, with respect to the leak, are important in acquiring clean signal.King Fahd University of Petroleum and Mineral

Characteristics of oxyfuel and air fuel combustion in an industrial water tube boiler

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.dc201