A Review of Multiphase Flow Through Chokes

1997 ◽  
Vol 119 (1) ◽  
pp. 1-10 ◽  
Author(s):  
S. Rastoin ◽  
Z. Schmidt ◽  
D. R. Doty
Keyword(s):  
Multiphase Flow ◽  
Flow Regime ◽  
Flow Direction ◽  
Absolute Error ◽  
Average Absolute Error ◽  
Subcritical Flow ◽  
Common Purpose ◽  
Critical Flow Regime ◽  
Flow Through ◽  
Good Agreement

Three comprehensive mechanistic models (Ashford and Pierce, 1974; Sachdeva et al., 1986; Perkins, 1990) dealing with multiphase flow through chokes have been studied. Their common purpose is to determine the flow through a choke under both critical and subcritical flow. Except for their initial assumptions, these three models are basically the same and all are based on the energy equation. Performance of the model developed by Perkins (1990) was the best in a comparison test against a database of 1239 points. The other two models deviated up to 40 percent when compared to the Perkins model for large values of choke to pipe size ratios. A very important application of these models is in prediction of the pressure either upstream or downstream of the choke, given the flow rate through the choke and the known pressure. Pressure predictions against the flow direction (i.e., upstream of the choke) were foundto be in very good agreement with measurements. Not more than 13 percent average absolute error and 17 percent standard deviation were observed. Similar errors were reported for the downstream pressure predictions for data in the subcritical flow regime. However, downstream pressure predictions for data in the critical flow regime gave large errors, up to 40 percent, which were expected.

The effect of two-phase flow regime on hydrodynamics and mass transfer in a horizontal-tube gas-liquid reactor

1985 ◽  
Vol 50 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Andreas Zahn ◽  
Lothar Ebner ◽  
Kurt Winkler ◽  
Jan Kratochvíl ◽  
Jindřich Zahradník
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Liquid Flow ◽  
Horizontal Tube ◽  
Liquid Holdup ◽  
Two Phase ◽  
Flow Rates ◽  
Type Relation ◽  
Good Agreement

The effect of two-phase flow regime on decisive hydrodynamic and mass transfer characteristics of horizontal-tube gas-liquid reactors (pressure drop, liquid holdup, kLaL) was determined in a cocurrent-flow experimental unit of the length 4.15 m and diameter 0.05 m with air-water system. An adjustable-height weir was installed in the separation chamber at the reactor outlet to simulate the effect of internal baffles on reactor hydrodynamics. Flow regime maps were developed in the whole range of experimental gas and liquid flow rates both for the weirless arrangement and for the weir height 0.05 m, the former being in good agreement with flow-pattern boundaries presented by Mandhane. In the whole range of experi-mental conditions pressure drop data could be well correlated as a function of gas and liquid flow rates by an empirical exponential-type relation with specific sets of coefficients obtained for individual flow regimes from experimental data. Good agreement was observed between values of pressure drop obtained for weirless arrangement and data calculated from the Lockhart-Martinelli correlation while the contribution of weir to the overall pressure drop was well described by a relation proposed for the pressure loss in closed-end tubes. In the region of negligible weir influence values of liquid holdup were again succesfully correlated by the Lockhart-Martinelli relation while the dependence of liquid holdup data on gas and liquid flow rates obtained under conditions of significant weir effect (i.e. at low flow rates of both phases) could be well described by an empirical exponential-type relation. Results of preliminary kLaL measurements confirmed the decisive effect of the rate of energy dissipation on the intensity of interfacial mass transfer in gas-liquid dispersions.

scholarly journals The conditions for occurrence of critical flow regime of water in the open stream

2019 ◽  
Vol 97 ◽  
pp. 05006
Author(s):  
Yuliya Bryanskaya ◽  
Aleksandra Ostiakova
Keyword(s):  
Froude Number ◽  
Flow Regime ◽  
Water Flow ◽  
Practical Interest ◽  
Open Water ◽  
Critical Regime ◽  
Critical Flow ◽  
Channel Processes ◽  
Channel Deformations ◽  
Critical Flow Regime

For the solution of engineering problems require increasingly accurate estimates of the hydraulic characteristics of the water streams. To date, it is impossible to consider sufficiently complete theoretical and experimental justification of the main provisions of the theory of turbulence, hydraulic resistance, channel processes. The composition of tasks related to flows in wide channels, turbulence problems are of scientific and practical interest. Various interpretations of the determination of the critical Froude number in wide open water flows based on observations and theoretical transformations are considered. The conditions for the emergence of a critical regime of water flow in an open wide channel are analyzed in order to estimate the critical Froude number and critical depth. Estimates of the critical Froude number for laboratory and field conditions are given. The estimations allow us to consider the proposed approach acceptable for determining the conditions of occurrence of the critical flow regime. The General, physical interpretation of conditions of occurrence of the critical regime of water flow on the basis of phenomenological approach is specified. The results take into account the values of the components of the total specific energy of the section. This shows the estimated calculation. The results obtained theoretically make it possible to compare the above interpretations and determine their applicability, and the results of the analysis can be useful for the estimated calculations of flows in channels and river flows in rigid, undeformable boundaries and with minor channel deformations.

Upward Vertical Two-Phase Flow Through an Annulus—Part II: Modeling Bubble, Slug, and Annular Flow

1992 ◽  
Vol 114 (1) ◽  
pp. 14-30 ◽  
Author(s):  
E. F. Caetano ◽  
O. Shoham ◽  
J. P. Brill
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through ◽  
Physical Phenomena ◽  
Good Agreement

Mechanistic models have been developed for each of the existing two-phase flow patterns in an annulus, namely bubble flow, dispersed bubble flow, slug flow, and annular flow. These models are based on two-phase flow physical phenomena and incorporate annulus characteristics such as casing and tubing diameters and degree of eccentricity. The models also apply the new predictive means for friction factor and Taylor bubble rise velocity presented in Part I. Given a set of flow conditions, the existing flow pattern in the system can be predicted. The developed models are applied next for predicting the flow behavior, including the average volumetric liquid holdup and the average total pressure gradient for the existing flow pattern. In general, good agreement was observed between the experimental data and model predictions.

Capillary water absorption by a porous cylinder

2017 ◽  
Vol 42 (2) ◽  
pp. 120-124 ◽  
Author(s):  
Christopher Hall
Keyword(s):  
Radial Flow ◽  
Effective Porosity ◽  
Capillary Absorption ◽  
Porous Cylinder ◽  
Capillary Water ◽  
Cylinder Axis ◽  
Flow Through ◽  
Front Model ◽  
Sharp Front ◽  
Good Agreement

Capillary absorption (imbibition) of water by a porous cylinder is described by means of a Sharp-Front model. The cumulative absorption increases as (time)1/2 at early times, but more slowly as the wet front approaches the cylinder axis. Results are given in terms of dimensionless variables. Experimental data on plaster cylinders are in good agreement with theory. Estimates of the sorptivity and effective porosity of the material can be obtained. The model may be useful in testing drilled cores and may also be applied to radial flow through the wall of a porous tube (hence to conduits and arches).

scholarly journals Assessment of Mercury-Polluted Soils Adjacent to an Old Mercury-Fulminate Production Plant

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
M. Camps Arbestain ◽  
L. Rodríguez-Lado ◽  
M. Bao ◽  
F. Macías
Keyword(s):  
Surface Waters ◽  
Contaminated Soils ◽  
Flow Direction ◽  
Surface Flow ◽  
Mercury Contamination ◽  
Production Plant ◽  
Polluted Soils ◽  
Flow Through ◽  
Contamination Of Soils ◽  
Surrounding Soil

Mercury contamination of soils and vegetation close to an abandoned Hg-fulminate production plant was investigated. Maximum concentrations of Hg (>6.5 gkg−1soil) were found in the soils located in the area where the wastewater produced during the washing procedures carried out at the production plant used to be discharged. A few meters away from the discharge area, Hg concentrations decreased to levels ranging between 1 and 5 gkg−1, whereas about 0.5 ha of the surrounding soil to the NE (following the dominant surface flow direction) contained between 0.1 and 1 gkg−1. Mercury contamination of soils was attributed (in addition to spills from Hg containers) to (i) Hg volatilization with subsequent condensation in cooler areas of the production plant and in the surrounding forest stands, and (ii) movement of water either by lateral subsurface flow through the contaminated soils or by heavy runoff to surface waters.

scholarly journals Homotopy Analysis Solution for Magnetohydrodynamic Squeezing Flow in Porous Medium

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Inayat Ullah ◽  
M. T. Rahim ◽  
Hamid Khan ◽  
Mubashir Qayyum
Keyword(s):  
Porous Medium ◽  
Control Parameter ◽  
Analytical Techniques ◽  
Squeezing Flow ◽  
Analysis Method ◽  
Homotopy Analysis ◽  
Convergence Control ◽  
Flow Through ◽  
Convergence Control Parameter ◽  
Good Agreement

The aim of the present work is to analyze the magnetohydrodynamic (MHD) squeezing flow through porous medium using homotopy analysis method (HAM). Fourth-order boundary value problem is modeled through stream functionψ(r,z)and transformationψ(r,z)=r2f(z). Absolute residuals are used to check the efficiency and consistency of HAM. Other analytical techniques are compared with the present work. It is shown that results of good agreement can be obtained by choosing a suitable value of convergence control parameterhin the valid regionRh. The influence of different parameters on the flow is argued theoretically as well as graphically.

scholarly journals Hidden Semi-Markov Models for Predictive Maintenance

2015 ◽  
Vol 2015 ◽  
pp. 1-23 ◽  
Author(s):  
Francesco Cartella ◽  
Jan Lemeire ◽  
Luca Dimiccoli ◽  
Hichem Sahli
Keyword(s):  
Markov Models ◽  
Real Data ◽  
Information Criterion ◽  
Absolute Error ◽  
Predictive Maintenance ◽  
Average Absolute Error ◽  
Current State ◽  
Automatic Model Selection ◽  
State Duration ◽  
Useful Lifetime

Realistic predictive maintenance approaches are essential for condition monitoring and predictive maintenance of industrial machines. In this work, we propose Hidden Semi-Markov Models (HSMMs) with (i) no constraints on the state duration density function and (ii) being applied to continuous or discrete observation. To deal with such a type of HSMM, we also propose modifications to the learning, inference, and prediction algorithms. Finally, automatic model selection has been made possible using the Akaike Information Criterion. This paper describes the theoretical formalization of the model as well as several experiments performed on simulated and real data with the aim of methodology validation. In all performed experiments, the model is able to correctly estimate the current state and to effectively predict the time to a predefined event with a low overall average absolute error. As a consequence, its applicability to real world settings can be beneficial, especially where in real time the Remaining Useful Lifetime (RUL) of the machine is calculated.

scholarly journals Study of a Privacy Preserving Logistic Regression Algorithm (PPLRA) For Data Privacy in the Context of Big Data

2021 ◽  
Vol 2083 (3) ◽  
pp. 032059
Author(s):  
Qiang Chen ◽  
Meiling Deng
Keyword(s):  
Machine Learning ◽  
Logistic Regression ◽  
Privacy Protection ◽  
Data Privacy ◽  
Absolute Error ◽  
Average Absolute Error ◽  
Regression Algorithms ◽  
Hadoop Platform ◽  
Logistic Regression Algorithm ◽  
Computing Speed

Abstract Regression algorithms are commonly used in machine learning. Based on encryption and privacy protection methods, the current key hot technology regression algorithm and the same encryption technology are studied. This paper proposes a PPLAR based algorithm. The correlation between data items is obtained by logistic regression formula. The algorithm is distributed and parallelized on Hadoop platform to improve the computing speed of the cluster while ensuring the average absolute error of the algorithm.

scholarly journals Short-Term Traffic Flow Forecasting Model Based on GA-TCN

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Rongji Zhang ◽  
Feng Sun ◽  
Ziwen Song ◽  
Xiaolin Wang ◽  
Yingcui Du ◽  
...  
Keyword(s):  
Neural Network ◽  
Genetic Algorithm ◽  
Convolutional Neural Network ◽  
Traffic Flow ◽  
Absolute Error ◽  
Forecasting Model ◽  
Average Absolute Error ◽  
Short Term ◽  
Traffic Flow Forecasting ◽  
Fitness Value

Traffic flow forecasting is the key to an intelligent transportation system (ITS). Currently, the short-term traffic flow forecasting methods based on deep learning need to be further improved in terms of accuracy and computational efficiency. Therefore, a short-term traffic flow forecasting model GA-TCN based on genetic algorithm (GA) optimized time convolutional neural network (TCN) is proposed in this paper. The prediction error was considered as the fitness value and the genetic algorithm was used to optimize the filters, kernel size, batch size, and dilations hyperparameters of the temporal convolutional neural network to determine the optimal fitness prediction model. Finally, the model was tested using the public dataset PEMS. The results showed that the average absolute error of the proposed GA-TCN decreased by 34.09%, 22.42%, and 26.33% compared with LSTM, GRU, and TCN in working days, while the average absolute error of the GA-TCN decreased by 24.42%, 2.33%, and 3.92% in weekend days, respectively. The results indicate that the model proposed in this paper has a better adaptability and higher prediction accuracy in short-term traffic flow forecasting compared with the existing models. The proposed model can provide important support for the formulation of a dynamic traffic control scheme.

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