Evaluation of numerical modelling for a compact down-hole subsea gas-liquid separator for high gas content

2009 ◽  
Vol 49 (1) ◽  
pp. 433
Author(s):  
Shakil Ahmed ◽  
Mohamed Nabil Noui-Mehidi ◽  
Jamal Naser's ◽  
Gerardo Sanchez Soto ◽  
Edson Nakagawa
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Volume Fraction ◽  
Air Flow ◽  
Gas Content ◽  
Water Mixture ◽  
Air Flow Rate ◽  
Flow Rates ◽  
High Efficient ◽  
Liquid Separator

This paper describes the computational fluid dynamics (CFD) modelling of a laboratory scale gas-liquid separator designed for high gas content. The separator consists of two concentric pipes with swirl tube in the annular space between the pipes. The gas-liquid mixture comes tangentially from the side inlet and the system works with a combination of gravity and centrifugal forces to achieve a high-efficient gas-liquid separation. Three dimensional transient multi-phase fluid flows were solved to predict the velocity and volume fraction of each phase. The standard k- turbulence model was used for turbulence closure. The performance of the gas-liquid separator was visually established for a range of gas flow rates (271–495 L/min), with volume fraction (VF) =0.874–0.985 by observing the liquid carry over (LCO) regime where liquid was carried out in the gas stream. The liquid and gas flow rates at which the LCO was observed defines the upper operational range of the separator. Air-water mixture was used in the numerical simulations to keep consistent with the experiments. The pressure between the inlet and exit was validated against the experiments for different air-water flow rate combinations. The values were matched reasonably well for high air flow rate (495 L/min, VF=0.985) but were under-predicted for low air flow rate (271 L/min, VF=0.874). The air and water were mixed upstream of the inlet in the experiments and the pressure was measured at the start of the inlet. In case of numerical simulation the air and water were mixed at the inlet. This might cause the deviation of pressure when the air flow rate was low.

Factors Impacting Liquid Droplet Instability in a PEFC Flow Channel

2006 ◽  
Author(s):  
Emin Caglan Kumbur ◽  
Kendra Vail Sharp ◽  
Matthew Michael Mench
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Liquid Droplet ◽  
Air Flow ◽  
Surface Hydrophobicity ◽  
Flow Channel ◽  
Low Flow ◽  
Unstable State ◽  
Air Flow Rate ◽  
Flow Rates

To achieve optimal performance with minimal parasitic losses and degradation, the relationship between water removal parameters such as flow rate and the diffusion media (DM) surface properties must be clearly identified. An extensive experimental study of the influence of controllable engineering parameters, including surface PTFE (Teflon™) coverage (ranging from 5% to 20% of wt.) and operational air flow rate, on liquid droplet deformation at the interface of the DM and the gas flow channel was performed. A new visualization technique was developed to better understand the droplet mechanisms with enhanced optical access of both side and top views of the flow channel of a simulated H2 PEFC. A telecentric lens and 5 mm by 5 mm prisms embedded in the flow channel side walls were used for the first time to measure droplet receding and advancing surface angles in an enclosed flow channel. The influence of channel air flow rate and emerging droplet size on droplet characteristics with varying PTFE content in the DM was investigated to identify the conditions under which the droplet tends toward an unstable state. The results indicate that operational conditions, droplet height, chord length, and level of surface hydrophobicity of the DM directly affect the droplet instability. At high flow rates, the surface hydrophobicity of the DM enhances the efficacy of droplet removal, and helps to avoid local channel flooding, however at low flow rates, regardless of the amount of PTFE content, droplet instability (and removal) is unaffected by the DM surface PTFE content.

Model-Based Analysis of Transient Behavior of Large Scale CFB Boilers

2003 ◽  
Author(s):  
Ari Kettunen ◽  
Timo Hyppa¨nen ◽  
Ari-Pekka Kirkinen ◽  
Esa Maikkola
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Air Flow ◽  
Model Parameters ◽  
Air Flow Rate ◽  
Process Data ◽  
Cfb Boiler ◽  
Flow Rates ◽  
Load Change ◽  
Secondary Air

The main objective of this study was to investigate the load change capability and effect of the individual control variables, such as fuel, primary air and secondary air flow rates, on the dynamics of large-scale CFB boilers. The dynamics of the CFB process were examined by dynamic process tests and by simulation studies. A multi-faceted set of transient process tests were performed at a commercial 235 MWe CFB unit. Fuel reactivity and interaction between gas flow rates, solid concentration profiles and heat transfer were studied by step changes of the following controllable variables: fuel feed rate, primary air flow rate, secondary air flow rate and primary to secondary air flow ratio. Load change performance was tested using two different types of tests: open and closed loop load changes. A tailored dynamic simulator for the CFB boiler was built and fine-tuned by determining the model parameters and by validating the models of each process component against measured process data of the transient test program. The know-how about the boiler dynamics obtained from the model analysis and the developed CFB simulator were utilized in designing the control systems of three new 262 MWe CFB units, which are now under construction. Further, the simulator was applied for the control system development and transient analysis of the supercritical OTU CFB boiler.

scholarly journals The effects of operating conditions on the performance of a direct carbon fuel cell

2013 ◽  
Vol 34 (4) ◽  
pp. 187-197 ◽  
Author(s):  
Andrzej Kacprzak ◽  
Rafał Kobyłecki ◽  
Zbigniew Bis
Keyword(s):  
Fuel Cell ◽  
Flow Rate ◽  
Gas Flow ◽  
Air Flow ◽  
Operating Conditions ◽  
Cell Performance ◽  
Fuel Particle ◽  
Air Flow Rate ◽  
Direct Carbon Fuel Cell ◽  
Fuel Particles

Abstract The influences of various operating conditions including cathode inlet air flow rate, electrolyte temperature and fuel particles size on the performance of the direct carbon fuel cell DCFC were presented and discussed in this paper. The experimental results indicated that the cell performance was enhanced with increases of the cathode inlet gas flow rate and cell temperature. Binary alkali hydroxide mixture (NaOH-LiOH, 90-10 mol%) was used as electrolyte and the biochar of apple tree origin carbonized at 873 K was used as fuel. Low melting temperature of the electrolyte and its good ionic conductivity enabled to operate the DCFC at medium temperatures of 723-773 K. The highest current density (601 A m−2) was obtained for temperature 773 K and air flow rate 8.3×106 m3s−1. Itwas shown that too low or too high air flow rates negatively affect the cell performance. The results also indicated that the operation of the DCFC could be improved by proper selection of the fuel particle size.

High-Accuracy Wet-Gas Multiphase Well Testing and Production Metering

SPE Journal ◽  
2006 ◽  
Vol 11 (02) ◽  
pp. 199-205 ◽  
Author(s):  
David I. Atkinson ◽  
Oyvind Reksten ◽  
Gerald Smith ◽  
Helge Moe
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Volume Fraction ◽  
Well Testing ◽  
Gas Flow Rate ◽  
Flow Rates ◽  
Wet Gas ◽  
New Interpretation ◽  
Interpretation Model

Summary Dedicated wet-gas flowmeters are now commercially available for the measurement of gas and liquid flow rates and offer a more compact measurement solution than does the traditional separator approach. The interpretation models of traditional multiphase flowmeters emphasize the liquid rate measurements and have been used to well test and meter mostly liquid-rich flow streams. These models were not developed for the measurement of gas flow rates, particularly those of wet gas. A new interpretation is described that allows a traditional multiphase flowmeter to operate in a dual mode either as a multiphase meter or as a wet-gas meter in 90 to 100% gas. The new interpretation model was developed for a commercially available multiphase flowmeter consisting of a venturi and a dual-energy composition meter. This combination results in excellent predictions of the gas flow rate; the liquid rate prediction is made with acceptable accuracy and no additional measurements. The wet gas and low-liquid-volume-fraction interpretation model is described together with the multiphase flowmeter. Examples of applying this model to data collected on flow loops are presented, with comparison to reference flow rates. The data from the Sintef and NEL flow loops show an error (including the reference meter error) in the gas flow rate, better than ± 2% reading (95% confidence interval), at line conditions; the absolute error (including the reference meter error) in the measured total liquid flow rate at line conditions was better than ± 2 m3/h (< ± 300 B/D: 95% confidence interval). This new interpretation model offers a significant advance in the metering of wet-gas multiphase flows and yields the possibility of high accuracies to meet the needs of gas-well testing and production allocation applications without the use of separators. Introduction There has been considerable focus in recent years on the development of new flow-measurement techniques for application to surface well testing and flow-measurement allocation in multiphase conditions without separating the phases. This has resulted in new technology from the industry for both gas and oil production. Today, there are wet-gas flowmeters, dedicated to the metering of wet-gas flows, and multiphase meters, for the metering of multiphase liquid flows. The common approach to wet-gas measurement relates gas and liquid flows to a "pseudo-gas flow rate" calculated from the standard single-phase equations. This addresses the need for gas measurement in the presence of liquids and can be applied to a limit of liquid flow [or gas volume fraction, (GVF)], though the accuracy of this approach decreases with decreasing GVF. The accurate determination of liquid rates by wet-gas meters is restricted in range. The application and performance of multiphase meters has been well documented through technical papers and industry forums, and after several years of development is maturing (Scheers 2004). Some multiphase measurement techniques can perform better, and the meters provide a more compact solution, than the traditional separation approach. It is not surprising that the use of multiphase flowmeters has grown significantly, the worldwide number doubling in little over a 2-year period (Mehdizadeh et al. 2002). Multiphase-flowmeter interpretation emphasizes the liquid rate measurement, and the application of multiphase flowmeters has been predominantly for liquid-rich flow stream allocation and well testing.

Coordinated control of fuel flow rate and air flow rate of a supersonic heat-airflow simulated test system

2020 ◽  
Vol 124 (1278) ◽  
pp. 1170-1189
Author(s):  
C. Cai ◽  
L. Guo ◽  
J. Liu
Keyword(s):  
Flow Rate ◽  
Control Algorithm ◽  
Air Flow ◽  
Coordinated Control ◽  
Test System ◽  
Gas Temperature ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Fuel Flow ◽  
Simulated Test

ABSTRACTThe gas temperature of the supersonic heat airflow simulated test system is mainly determined by the fuel and air flow rates which enter the system combustor. In order to realise a high-quality control of gas temperature, in addition to maintaining the optimum ratio of fuel and air flow rates, the dynamic characteristics of them in the combustion process are also required to be synchronised. Aiming at the coordinated control problem of fuel and air flow rates, the mathematical models of fuel and air supply subsystems are established, and the characteristics of the systems are analysed. According to the characteristics of the systems and the requirements of coordinated control, a fuzzy-PI cross-coupling coordinated control strategy based on neural sliding mode predictive control is proposed. On this basis, the proposed control algorithm is simulated and experimentally studied. The results show that the proposed control algorithm has good control performance. It cannot only realise the accurate control of fuel flow rate and air flow rate, but also realise the coordinated control of the two.

scholarly journals POLYMER WASTES’ FLOTATION SEPARATION RESEARCH RESULTS

2020 ◽  
Vol 6 (444) ◽  
pp. 50-58
Author(s):  
А. Volnenko ◽  
◽  
А. Leudanski ◽  
Y. Apimakh ◽  
B. Korganbayev ◽  
...  
Keyword(s):  
Liquid Layer ◽  
Flow Rate ◽  
Air Flow ◽  
Liquid Temperature ◽  
Air Flow Rate ◽  
Flotation Process ◽  
Flow Rates ◽  
Research Results ◽  
Air Bubble ◽  
Plastic Wastes

For separation of plastic wastes (polyamide (PA), acrylonitrile butadiene styrene (ABS) and polystyrene (PS), a flotation method is proposed. Using this method, the effect of concentration of surface-active substances (surfactants), which were used as polidocanol, sulphanole and a mixture of surfactants containing sodium laureth sulfate and diethanolamide, was studied. The research results analysis of the flotation separation of a mixture of crushed plastic wastes was carried out according to the calculated values of the extraction of a floated component ε and the purity of a concentrate β. It was noted that the maximum extraction of the floated component depends on the polymer and surfactant type. A mixture of surfactants at lower concentrations allows to achieve greater extraction of the floated component with less foaming ability. The research results on the extraction of polystyrene from the air flow rate at various concentrations of surfactants’ mixture show that the extraction has a maximum at a certain air flow rate. At low air flow rates, the working volume of liquid is not saturated enough with gas bubbles. If the optimal value of air flow rates is exceeded, many gas bubbles are formed that are not involved in the flotation process. The research results on the extraction of polystyrene from the aerated liquid layer height at various concentrations of surfactants’ mixture show that, at a low height of the aerated liquid layer, the probability of collision of a plastic particle with an air bubble is low and some potentially floated particles seek the bottom of an apparatus without having time to collide with an air bubble. When assessing the influence of liquid temperature on the flotation process, it was found that increasing the liquid temperature above 20°C leads to a sharp decrease in ABS and PS extraction. This is explained by the fact that the dependence of the surfactants’ foaming ability on the temperature is characterized by solubility curves and for most surfactants they have an extremum.

scholarly journals Evaluation of Izmir Tulum cheese pieces by drying with tray drier at different air flow rates and temperatures

2018 ◽  
Author(s):  
Nurcan Koca ◽  
Gulsah Kizilalp ◽  
Izel Polat ◽  
Müge Urgu
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Sensory Properties ◽  
Water Holding Capacity ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Physical Chemical ◽  
Tulum Cheese ◽  
Water Holding

Izmir tulum cheese pieces were dried using a tray dryer at different air flow rates (1.0 and 1.8 m/s) and temperatures (45oC, 55oC and 65oC). The increase in temperature and air flow rate increased bulk and tapped bulk densityand decreased the water holding capacity. The lowest lightness and highest redness were obtained in samples dried at 65oC. The samples dried at 55°C and 1 m/s had the highest flavor and overall impression scores. As a result, a dried cheese product to benefit from left-over pieces obtained during packaging  was developed, having advantages such as easy to transport, store and package.Keywords: Izmir Tulum cheese; tray dryer; physical, chemical and sensory properties.   

Effect of pressure and salinity on the performance of a gas-liquid separator—a preliminary study

2011 ◽  
Vol 51 (1) ◽  
pp. 603 ◽  
Author(s):  
Shakil Ahmed ◽  
Gerardo Sanchez-Soto ◽  
Chong Wong ◽  
Edson Nakagawa ◽  
Jamal Naser
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Water Flow Rate ◽  
Water Mixture ◽  
Gas Flow Rate ◽  
Cfd Modelling ◽  
Effect Of Pressure ◽  
Compact Design ◽  
Operational Range ◽  
Liquid Separator

The separation of liquid from gas during the initial stages of the separation process is very important in increasing well productivity. This is why the design of an efficient and compact gas-liquid separator has received much attention from academic researchers as well as field operators. They all state the necessity of compact design in deploying separators offshore (and potentially subsea) to enhance the recovery of gas wells. This investigation describes an experimental and computational fluid dynamics (CFD) modelling of a laboratory-scale compact gas-liquid separator designed by CSIRO. The separator consists of two concentric pipes with a swirl tube in the annular space between the pipes. The gas-liquid mixture comes from the tangential side inlet, and the system works with a combination of gravity and centrifugal forces to achieve a highly efficient gas-liquid separation. The effect of pressure and salinity on the performance of the gas-liquid CSIRO’s separation technology (CS-T) separator is investigated in this paper. The performance of the separator is visually established by observing the liquid carry over (LCO) regime in which liquid is carried out in the gas stream. The liquid and gas-flow rate at which the LCO is observed defines the upper operational range of the separator. Air-water mixture is used for both experimental and CFD investigations. The performance is evaluated at 1, 2, 5, 10 and 12 barg pressure. The upper operational range decreases with increases in pressure. For higher pressure (10 and 12 barg), the LCO curve was nearly vertical, which indicates no change in gas-flow rate with the increase in water flow rate. Salinity does not affect the performance of the CS-T separator. The CFD results are used to visualise the continuous LCO and to understand the physics and mechanism of LCO.

Improving the estimation of methodological errors in reproducing the volumetric air flow rate by reference critical nozzle

Metrologiya ◽  
2021 ◽  
pp. 4-30
Author(s):  
V. I. Chesnokov
Keyword(s):  
Kinetic Energy ◽  
Flow Rate ◽  
Gas Flow ◽  
Flow Model ◽  
Air Flow ◽  
Operating Conditions ◽  
Initial Kinetic Energy ◽  
Methodological Error ◽  
Air Flow Rate ◽  
Critical Nozzle

In the development of the previously obtained results a more accurate estimate of the methodological error in reproducing the volumetric air flow rate by reference critical nozzle is given, associated with the choice of the gas flow model and due to taking into account the initial kinetic energy of the flow at the nozzle inlet. Based on improved flow model an analytical evaluation of the methodological error in reproducing the volumetric air flow rate by reference critical nozzle, which is due to a change in the humidity of the working air, has been carried out. It is shown that the methodological error in reproducing the volumetric air flow rate by reference critical nozzle, associated with a change in the air humidity, as well as the analogies methodical error caused by the existence of the initial kinetic energy of the flow, must be taken part in accuracy characteristics at the real operating conditions of the standard volumetric air flow rate using critical nozzles.

Two-Phase Flow Visualization for a Hybrid Heat Sink

2018 ◽  
Author(s):  
Danish Rahman ◽  
Ahmad Almomani ◽  
Ibrahim Hassan ◽  
Yasser Al-Hamidi ◽  
Aziz Rahman
Keyword(s):  
Flow Rate ◽  
Slug Flow ◽  
Air Flow ◽  
Plug Flow ◽  
Cross Flow ◽  
Flow Regimes ◽  
Air Flow Rate ◽  
Two Phase ◽  
Flow Rates ◽  
Impingement Jet

This paper aimed to study two-phase flow under adiabatic conditions through the process of flow visualization. This was done through the use of a test section with a cross flow and a jet impingement (swirl jet). The flow regimes under different air-water flow rates were determined using a high-speed camera that recorded digital videos. For each of the flow rates the pressure differential between the inlet and the outlets were measured. Through the pressure drop it is proposed that the types of flow regimes may later be able to be predicted. Nine air-water flow rates were considered to collect data and generate a flow map for the impingement jet and cross flow. The major observed flow regimes within the crossflow and impingement jet followed the predicted trend with bubbly and plug flow in the former, and slug flow in the latter. It was further observed that increasing the air flow rate increased the likelihood of bubbly and plug flow in both the cross-flow and impingement jet. In the cross flow, a lower air flow rate resulted in bubbly flow while within the impingement jet, a lower air flow rate resulted in slug flow.

Sign in / Sign up

Export Citation Format

Share Document