Characteristics of horizontal gas-liquid two-phase flow measurement in a medium-sized pipe using gamma densitometry

Two-phase flows are common occurrences in many industrial applications. The understanding of their characteristics in industrial piping systems is vital for the efficient design, optimization, and operation of industrial processes. Most of the previous experimental studies involving the use of gamma densitometers for holdup measurements in air-water mixtures are limited to smaller diameter pipes (generally regarded as those with < 50 mm in nominal diameter). Further, very few literature report experimental data obtained using gamma desitometers. This paper presents an application of a gamma densitometer in the measurement of two-phase flow characteristics in an intermediate diameter pipe (nominal diameter between 50 mm and 100 mm). Scaled air-water experiments were performed in a 17-m long, 0.0764-m internal diameter horizontal pipe. Liquid superficial velocity ranged between 0.1–0.4 m/s while gas superficial velocity ranged from 0.3 to 10.0 m/s. The measured parameters include liquid holdup, pressure gradient, flow pattern, and slug flow features. The flow patterns observed were stratified, stratified-wavy, plug, slug, and annular flows. Plug and slug flow patterns showed good agreement with established flow pattern maps. Furthermore, the slug translational velocity was observed to increase with increasing mixture velocity, as reported by previous authors, hence establishing the reliability of the instrumentation employed. The slug body length was also measured using the gamma densitometer and was found to be within the range 24–36D with a mean length of 30.6D

Experimental Investigation of Flow Condensation of Propylene in a horizontal Tube

openLa condensazione durante deflusso è un processo fisico molto diffuso, utilizzato nei condensatori adottati per diverse applicazioni come pompe di calore, impianti di condizionamento e nell’industria chimica. L'esigenza dell'industria della refrigerazione di trovare refrigeranti alternativi a HFC, caratterizzati da un ODP quasi nullo ma da un GWP troppo elevato, rende molto importante lo studio degli idrocarburi per le applicazioni a ciclo inverso. L'obiettivo del presente lavoro è studiare la condensazione del flusso di propilene all'interno di un tubo orizzontale liscio. La condensazione in flusso è un meccanismo di trasferimento del calore molto complesso che attualmente non può essere descritto da equazioni analitiche. Pertanto, l'analisi sperimentale diventa uno strumento importante per convalidare le correlazioni presentate in letteratura. Il lavoro sperimentale è stato condotto sfruttando un impianto di prova su scala industriale, il KIIR, che consente di impostare le condizioni termodinamiche all'ingresso della sezione di prova, dove avviene la condensazione parziale. La sezione di prova consiste in uno scambiatore di calore a fascio tubiero. Il propilene viene raffreddato da un olio in configurazione di flusso controcorrente. Il tubo sperimentale è stato dotato di sensori di temperatura e installato all’interno dell'apparato sperimentale. Ciascun test è stato eseguito in condizioni operative costanti in termini di pressione p, flusso di massa G e titolo di vapore x. L'analisi dei risultati a livello locale ha permesso di dimostrare la dipendenza del coefficiente di trasferimento di calore α dalla posizione radiale φ del tubo. In particolare, nelle condizioni di prova associate al verificarsi di un flusso stratificato, il coefficiente di trasferimento di calore α varia notevolmente in funzione della posizione radiale φ. Nelle condizioni di alta turbolenza e flusso anulare, il coefficiente di trasferimento di calore α è approssimativamente costante in funzione della posizione radiale φ. A causa delle incertezze del set-up sperimentale, queste osservazioni sono state più chiare nelle condizioni di prova in cui la differenza di temperatura media tra la sostanza in esame e l'olio di raffreddamento era più elevata. Inoltre, è stato possibile verificare sperimentalmente che il coefficiente di trasferimento del calore α aumenta all'aumentare del flusso di massa G. Allo stesso modo, è stato possibile verificare che il coefficiente di trasferimento di calore α diminuisce con l'aumento della pressione p. Confrontando i risultati relativi al trasferimento di calore complessivo e alle perdite di carico, si è dedotto che un elevato coefficiente di trasferimento di calore è sempre abbinato a un alto valore di perdite di carico.Flow condensation is a very widely spread physical process, used in condensers adopted for several applications like heat pumps, air conditioning systems, and the chemical industry. The urge of the refrigeration industry to find alternative refrigerants to HFC, characterized by null ODP but too high GWP, makes the study of hydrocarbons for inverse cycle applications very important. The goal of the present work is to study flow condensation of propylene inside a horizontal smooth tube. Flow condensation is a very complex heat transfer mechanism that currently, cannot be described by analytical equations. Therefore, experimental analysis becomes an important tool to validate the correlations presented in the literature. The present experimental work has been conducted exploiting an industrial scale test rig, KIIR, that allows to set the thermodynamics conditions at the inlet of the test section, where partial condensation occurs. The test section consists in a tube-shell-heat exchanger. Propylene is cooled down by an oil in counter-current flow configuration. The test tube has been equipped with temperature sensors and installed in the experimental apparatus and the measurement plan has been conducted. Each test has been executed under constant operating conditions in terms of pressure p, mass flux G and vapor quality x. The analysis of the local experimental results has allowed to observe the dependency of the heat transfer coefficient α on the radial position φ of the test tube. Specifically, under test conditions associated with the occurrence of stratified flow, the heat transfer coefficient α varies considerably as function of the radial position φ. Under the conditions associated with high turbulence and annular flow, the heat transfer coefficient α is approximately constant as function of the radial position φ. Because of the uncertainties of the experimental set up, these observations were clearer under the test conditions in which the average temperature difference between the test substance and the cooling oil was higher. Moreover, it was observed that the overall heat transfer coefficient α increases as the mass flux G increases. In the same way, it was possible to observe that the overall heat transfer coefficient α decreases as the pressure p increases. By comparing the results regarding overall heat transfer and pressure drops, it was verified that a high heat transfer coefficient is always coupled with a high value of pressure drops

COMPUTATIONAL FLUID DYNAMIC (CFD) SIMULATION OF SLUG FLOW WITHIN PIPE BEND AND PIPE ELBOW WHICH INDUCE VIBRATION

Multi-phase flow is any fluid stream consisting of more than one phase or component, for example, gas-liquid stream, liquid-liquid flow, solid fluid stream, or solid-fluid gas stream. It is common in fluid systems, in particular in oil and gas hydrocarbon conveying systems which produce natural gas and crude oil at the same time. A significant response from flux-induced vibration can lead to potential fatigue damage or uncontrolled vibration when the frequency of excitation matches the piping system's natural frequencies, especially in cases where oil produces dense sand particles or slow flows in the flow-lines. This is why it is important to investigate the impact of the oil-gas-water mix on pipeline structure

Dynamics of the free surface of stratified two-phase flows in channels with rectangular cross-sections

Stratified two-phase flows were investigated at different test facilities with horizontal test sections in order to provide an experimental database for the development and validation of computational fluid dynamics (CFD) codes. These channels were designed with rectangular cross-sections to enable optimal observation conditions for the application of optical measurement techniques. Consequently, the local flow structure was visualised with a high-speed video camera, delivering data with high-resolution in space and time as needed for CFD code validation. Generic investigations were performed at atmospheric pressure and room temperature in two air/water channels made of acrylic glass. Divers preliminary experiments were conducted with various measuring systems in a test section mounted between two separators. The second test facility, the Horizontal Air/Water Channel (HAWAC), is dedicated to co-current flow investigations. The hydraulic jump as the quasi-stationary discontinuous transition between super- and subcritical flow was studied in this closed channel. Moreover, the instable wave growth leading to slug flow was investigated from the test section inlet. For quantitative analysis of the optical measurements, an algorithm was developed to recognise the stratified interface in the camera frames, allowing statistical treatments for comparison with CFD calculation results. The third test apparatus was installed in the pressure chamber of the TOPFLOW test facility in order to be operated at reactor typical conditions under pressure equilibrium with the vessel atmosphere. The test section representing a flat model of the hot leg of the German Konvoi pressurised water reactor (PWR) scaled at 1:3 is equipped with large glass side walls in the region of the elbow and of the steam generator inlet chamber to allow visual observations. The experiments were conducted with air and water at room temperature and maximum pressures of 3 bar as well as with steam and water at boundary conditions of up to 50 bar and 264°C. Four types of experiments were performed, including generic test cases as well as transient validation cases of typical nuclear reactor safety issues. As an example, the co-current flow experiments simulate the two-phase natural circulation in the primary circuit of a PWR. The probability distribution of the water level measured in the reactor pressure vessel simulator was used to characterise the flow in the hot leg. Moreover, the flooding behaviour in this conduit was investigated with dedicated counter-current flow limitation experiments. A comparison of the flooding characteristics with similar experimental data and correlations available in the literature shows that the channel height is the characteristic length to be used in the Wallis parameter for channels with rectangular cross-sections. Furthermore, for the analysis of steam/water experiments, condensation effects had to be taken into account. Finally, the experimental results confirm that the Wallis similarity is appropriate to scale flooding in the hot leg of a PWR over a large range of pressure and temperature conditions. Not least, different examples of comparison between experiment and simulation demonstrate the possibilities offered by the data to support the development and validation of CFD codes. Besides the comparison of qualitative aspects, it is shown exemplarily how to treat the CFD results in order to enable quantitative comparisons with the experiments

Experimental Investigation of Annular Flow Behaviour in Horizontal Pipe

The experimental investigations of annular flow were conducted in horizontal pipe using water/air in a 0.0504m internal diameter pipe loop with a total length of 28.68m. To understand annular flow behaviors, conductivity ring sensors, conductance probe sensors and Olympia high speed digital camera&nbsp;were used. In all the experiments, emphasis were on annular flow behavior, phase distribution and liquid film thickness. Liquid film thickness was observed to be thicker mostly when the superficial gas velocities were within 8.2699 m/s to 12.0675 m/s. &nbsp;Above the aforementioned superficial gas velocities, the flow became uniformly distributed on the walls of the internal pipe diameter hence reducing the thicker liquid film at the bottom with gas core at the center of the pipe. More so, annular-slug flow was discovered in the investigation. At superficial liquid velocity of 0.0505 m/s-0.1355 m/s on superficial gas velocities of 8.2699 m/s – 12.0675 m/s, annular-slug flow was prominent. Also discovered was at superficial liquid velocities of 0.0903 m/s - 0.1355 m/s with respect to superficial gas velocities of 13.1692 m/s – 23.4575 m/s, the pipe walls are fully covered with liquid film at very high speed at the entire walls (upper walls and bottom). Also discovered in this experiment is the wavy flow of the upper walls. The liquid film thickness that flows at the upper pipe walls, creeps in a wavy flow. Therefore, the entire flow behavior in an annular flow could be grouped into; wavy-flow at the upper walls, annular-slug flow and thicker liquid film at the bottom with gas core at the center

The Effects of Tank Operation and Design Characteristics on Water Quality in Distribution System Storage Tanks

From the Executive Summary Background: Regional water systems utilize storage facilities to meet demand variations and pressure requirements of their systems. These storage facilities drain and fill in response to system water demands and water level control settings. Storage tanks are typically placed in strategic locations to maintain a consistent pressure in the distribution system. Storage facilities should be designed and operated such that the water is mixed to prevent stagnant water (old water that remains in the tank for an extended period). Stagnant water can lead to water quality issues, such as low disinfectant residuals, potential for microbial contamination, disinfectant by-product formation, and nitrification in chloraminated waters. Many tanks have been built without consideration of mixing. These tanks might have a single inlet/outlet, high height to diameter ratio, or have other design characteristics that do not promote mixing. Whether by design or not, tanks without artificial mixing depend upon movement of water during the filling process to mix the tank. A wide array of storage tank types and geometries are utilized in South Dakota’s regional rural water systems. Greater understanding of the relationships of these tank characteristics on stored water quality would enable water systems to optimize the design and operation of their tanks. Objective of Study:The objective of this study was to examine the impacts of tank design and operation on mixing and water quality in storage tanks in South Dakota’s regional rural water systems. This objective was met through a literature review, a survey of system characteristics and evaluation of water quality data obtained from several storage tanks

TWO PHASE FLOW EXPERIMENTAL DETECTION METHOD AND CFD MODELS – A REVIEW

Liquid two-phase flow has been studied widely by many authors. Two phase flow exist in petroleum industries, nuclear power generation and chemical plants. In the present study a review on two phase flow such as oil/water was discussed, also the patterns of the flow and types of measurement are presented. Also a review on the new trends using the computational fluid dynamic (CFD) to predict the liquid-liquid two phase are viewed

High-viscosity biphasic flow characterization in a pipeline: application to flow pattern classification and leak detection

Pipeline systems play an essential role in the oil industry. These systems connect ports, oil fields, refineries, and consumer markets[104]. Pipelines covering long distances require pumping stations, where products are propelled to the next pumping station, refinery, or deposit terminal, thus traveling through most of the country. The product considered in this research work is crude oil. It is usually transported with a combination of crude oil with viscosity reducers (DRA, drag reducer agent) and oil with gas in onshore/offshore pipelines. This mode of transport is efficient for large quantities and large product shipment distances. Problems may arrive when a leak occurs. In major incidents, large scale damage to humans and the environment is possible. Then, this research addresses the problem of how to detect the leak earlier to reduce the impact in the surrounding areas and economic losses, considering five research topics taking into account that the products inside the pipeline are water-glycerol and gas-glycerol mixtures (simulating oil-DRA and oil-gas in the laboratory test apparatus). The first research topic presents a mathematical model to describe the flow of a mixture of water and glycerol in pressurized horizontal pipelines, which emulates the mixture of heavy oil and a viscosity reducer. The model is based on the mass and momentum conservation principles and empirical correlations for the mixture’s density and viscosity. The set of partial differential equations is solved using finite differences. These equations were implemented in a computer platform to be able to simulate a system. This simulation platform is a tool to simulate leak cases for different fractions of water and glycerol to evaluate algorithms for leak detection and localization before their implementation in a laboratory setting.DoctoradoDoctor en Ingeniería Mecánic

Measurement of Water in Oil Pipelines using Capacitance Method

This project entitled “Measurement of Water in Oil Pipelines using Capacitance Method” is closely related to oil & gas industry especially from the aspect of safety. To minimize the internal corrosion of oil pipelines due to the presence of water, capacitance method is introduced to detect the amount of water present in oil-water mixture. Being cheap, safe and non- intrusive, this method is suitable for two-phase fluids with low conductivity and large permittivity difference such as oil and water. However, different configurations of electrodes will produce different results in terms of linearity of response. In this project, by utilising ANSYS Maxwell software, two common configurations of electrodes i.e. concave and double rings electrodes are designed to compare their linearity of response towards changes in water content in oil-water mixture