Search results

1 – 10 of over 7000
To view the access options for this content please click here
Article
Publication date: 1 January 2005

Pradeep Hegde, K.N. Seetharamu, G.A. Quadir, P.A. Aswathanarayana, M.Z. Abdullah and Z.A. Zainal

To analyze two‐phase flow in micro‐channel heat exchangers used for high flux micro‐electronics cooling and to obtain performance parameters such as thermal resistance…

Abstract

Purpose

To analyze two‐phase flow in micro‐channel heat exchangers used for high flux micro‐electronics cooling and to obtain performance parameters such as thermal resistance, pressure drop, etc. Both uniform and non‐uniform micro‐channel base heat fluxes are considered.

Design/methodology/approach

Energy balance equations are developed for two‐phase flow in micro‐channels and are solved using the finite element method (FEM). A unique ten noded element is used for the channel descritization. The formulation also automatically takes care of single‐phase flow in the micro‐channel.

Findings

Micro‐channel wall temperature distribution, thermal resistance and the pressure drop for various uniform micro‐channel base heat fluxes are obtained, both for single‐ and two‐phase flows in the micro‐channel. Results are compared against data available in the literature. The wall temperature distribution for a particular case of non‐uniform base heat flux is also obtained.

Research limitations/implications

The analysis is done for a single micro‐channel and the effects of multiple or stacked channels are not considered. The analysis needs to be carried out for higher heat fluxes and the validity of the correlation needs to be ascertained through experimentation. Effects of flow mal‐distribution in multiple channels, etc. need to be considered.

Practical implications

The role of two‐phase flow in micro‐channels for high flux micro‐electronics cooling in reducing the thermal resistance is demonstrated. The formulation is very useful for the thermal design and management of microchannels with both single‐ and two‐phase flows for either uniform or non‐uniform base heat flux.

Originality/value

A simple approach to accurately determine the thermal resistance in micro‐channels with two‐phase flow, for both uniform and non‐uniform base heat fluxes is the originality of the paper.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 15 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 8 July 2011

Baabak Ashuri, Jian Lu and Hamed Kashani

This paper aims to present a financial valuation framework based on the real options theory to evaluate investments in toll road projects delivered under the two‐phase

Abstract

Purpose

This paper aims to present a financial valuation framework based on the real options theory to evaluate investments in toll road projects delivered under the two‐phase development plan.

Design/methodology/approach

The approach is based on applying the real options theory to evaluate investments in toll road projects. In particular, the risk‐neutral valuation method is used for pricing flexibility embedded in the two‐phase development plan. Risk‐neutral binomial lattice is used to model traffic uncertainty and to find the optimal time for the toll road expansion. Probabilistic life cycle cost and revenue analysis is conducted to characterize the investor's financial risk profile and determine the flexibility value of the expansion option.

Findings

The flexible, two‐phase development plan can improve the investor's financial risk profile in the toll road project through limiting the downside risk of overinvestment (i.e. decreasing the probability of investment loss) and increasing the expected investment value in a highway project.

Social implications

Private and public sectors can benefit from this valuation framework and use tax dollars and users' fees effectively through avoiding overinvestment in toll road projects.

Originality/value

The framework consists of several integrated features, which distinguish it from existing investment valuation models. The risk‐neutral valuation method for pricing flexibility embedded in the two‐phase development plan is applied. This real options framework is capable of characterizing traffic boundary, at which it is optimal for the investor to expand the toll road. Further, this framework provides the likelihood distribution of when the investor may expand the toll road.

To view the access options for this content please click here
Article
Publication date: 1 June 1993

K.V. PRASHANTH and K.N. SEETHARAMU

A mathematical model is developed for the description of the thermohydraulics of the two‐phase flow phenomenon in a vertical pipe. Using an additional momentum equation…

Abstract

A mathematical model is developed for the description of the thermohydraulics of the two‐phase flow phenomenon in a vertical pipe. Using an additional momentum equation for the slip velocity, it is shown that the computation of slip and pressure drop from the model equations is possible without the use of any external correlations. The finite element method is used to solve the governing equations. The predictions for a steam‐water two‐phase flow in vertical upflow with constant wall heat flux agree well with experimental results and with widely used correlations.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 3 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 4 February 2019

Tao Xue, Xiaobing Zhang and K.K. Tamma

A consistent implementation of the general computational framework of unified second-order time accurate integrators via the well-known GSSSS framework in conjunction with…

Abstract

Purpose

A consistent implementation of the general computational framework of unified second-order time accurate integrators via the well-known GSSSS framework in conjunction with the traditional Finite Difference Method is presented to improve the numerical simulations of reactive two-phase flows.

Design/methodology/approach

In the present paper, the phase interaction evaluation in the present implementation of the reactive two-phase flows has been derived and implemented to preserve the consistency of the correct time level evaluation during the time integration process for solving the two phase flow dynamics with reactions.

Findings

Numerical examples, including the classical Sod shock tube problem and a reactive two-phase flow problem, are exploited to validate the proposed time integration framework and families of algorithms consistently to second order in time accuracy; this is in contrast to the traditional practices which only seem to obtain first-order time accuracy because of the inconsistent time level implementation with respect to the interaction of two phases. The comparisons with the traditional implementation and the advantages of the proposed implementation are given in terms of the improved numerical accuracy in time. The proposed approaches provide a correct numerical simulation implementation to the reactive two-phase flows and can obtain better numerical stability and computational features.

Originality/value

The new algorithmic framework and the consistent time level evaluation extended with the GS4 family encompasses a multitude of past and new schemes and offers a general purpose and unified implementation for fluid dynamics.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 5 February 2018

Gino Cortellessa, Fausto Arpino, Simona Di Fraia and Mauro Scungio

In this work, a new two-phase version of the finite element-based Artificial Compressibility (AC) Characteristic-Based Split (CBS) algorithm is developed and applied for…

Abstract

Purpose

In this work, a new two-phase version of the finite element-based Artificial Compressibility (AC) Characteristic-Based Split (CBS) algorithm is developed and applied for the first time to heat and mass transfer phenomena in porous media with associated phase change. The purpose of this study is to provide an alternative for the theoretical analysis and numerical simulation of multiphase transport phenomena in porous media. Traditionally, the more complex Separate Flow Model was used in which the vapour and liquid phases were considered as distinct fluids and mathematically described by the conservation laws for each phase separately, resulting in a large number of governing equations.

Design/methodology/approach

Even though the adopted mathematical model presents analogies with the conventional multicomponent mixture flow model, it is characterized by a considerable reduction in the number of the differential equations for the primary variables. The fixed-grid numerical formulation can be applied to the resolution of general problems that may simultaneously include a superheated vapour region, a two-phase zone and a sub-cooled liquid region in a single physical domain with irregular and moving phase interfaces in between. The local thermal non-equilibrium model is introduced to consider the heat exchange between fluid and solid within the porous matrix.

Findings

The numerical model is verified considering the transport phenomena in a homogenous and isotropic porous medium in which water is injected from one side and heated from the other side, where it leaves the computational domain in a superheated vapour state. Dominant forces are represented by capillary interactions and two-phase heat conduction. The obtained results have been compared with the numerical data available in the scientific literature.

Social implications

The present algorithm provides a powerful routine tool for the numerical modelling of complex two-phase transport processes in porous media.

Originality/value

For the first time, the stabilized AC-CBS scheme is applied to the resolution of compressible viscous flow transport in porous materials with associated phase change. A properly stabilized matrix inversion-free procedure employs an adaptive local time step that allows acceleration of the solution process even in the presence of large source terms and low diffusion coefficients values (near the phase change point).

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 1996

D.M. Lu, H.C. Simpson and A. Gilchrist

An easy‐to‐use numerical model for transient two‐phase pipe flowanalyses was developed by applying the split‐coefficient matrix method (SCMM)to a homogeneous equilibrium…

Abstract

An easy‐to‐use numerical model for transient two‐phase pipe flow analyses was developed by applying the split‐coefficient matrix method (SCMM) to a homogeneous equilibrium two‐phase flow model. The basic idea of the SCMM is to split the Jacobian coefficient matrix into two sub‐vectors, each associated with eigenvalues of the same sign. Hence, one‐sided finite difference schemes can accordingly be applied to the sub‐vectors. The present model was validated against experiments. It is numerically stable provided that a criterion is met due to the use of a time explicit format. The satisfactory agreement between the numerical and experimental results indicates that the model may be used as a simple, efficient tool for general engineering analyses of transient two‐phase flow. The advantages of applying SCMM to transient two phase flows are briefly addressed, and it is applicable to systems having real eigenvalues.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 6 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 11 April 2020

Bo Li, Jian ming Wang, Qi Wang, Xiu yan Li and Xiaojie Duan

The purpose of this paper is to explore gas/liquid two-phase flow is widely existed in industrial fields, especially in chemical engineering. Electrical resistance…

Abstract

Purpose

The purpose of this paper is to explore gas/liquid two-phase flow is widely existed in industrial fields, especially in chemical engineering. Electrical resistance tomography (ERT) is considered to be one of the most promising techniques to monitor the transient flow process because of its advantages such as fast respond speed and cross-section imaging. However, maintaining high resolution in space together with low cost is still challenging for two-phase flow imaging because of the ill-conditioning of ERT inverse problem.

Design/methodology/approach

In this paper, a sparse reconstruction (SR) method based on the learned dictionary has been proposed for ERT, to accurately monitor the transient flow process of gas/liquid two-phase flow in a pipeline. The high-level representation of the conductivity distributions for typical flow regimes can be extracted based on denoising the deep extreme learning machine (DDELM) model, which is used as prior information for dictionary learning.

Findings

The results from simulation and dynamic experiments indicate that the proposed algorithm efficiently improves the quality of reconstructed images as compared to some typical algorithms such as Landweber and SR-discrete fourier transformation/discrete cosine transformation. Furthermore, the SR-DDELM has also used to estimate the important parameters of the chemical process, a case in point is the volume flow rate. Therefore, the SR-DDELM is considered an ideal candidate for online monitor the gas/liquid two-phase flow.

Originality/value

This paper fulfills a novel approach to effectively monitor the gas/liquid two-phase flow in pipelines. One deep learning model and one adaptive dictionary are trained via the same prior conductivity, respectively. The model is used to extract high-level representation. The dictionary is used to represent the features of the flow process. SR and extraction of high-level representation are performed iteratively. The new method can obviously improve the monitoring accuracy and save calculation time.

Details

Sensor Review, vol. 40 no. 4
Type: Research Article
ISSN: 0260-2288

Keywords

To view the access options for this content please click here
Article
Publication date: 4 November 2019

Jingfa Li, Tao Zhang, Shuyu Sun and Bo Yu

This paper aims to present an efficient IMPES algorithm based on a global model order reduction method, proper orthogonal decomposition (POD), to achieve the fast solution…

Abstract

Purpose

This paper aims to present an efficient IMPES algorithm based on a global model order reduction method, proper orthogonal decomposition (POD), to achieve the fast solution and prediction of two-phase flows in porous media.

Design/methodology/approach

The key point of the proposed algorithm is to establish an accurate POD reduced-order model (ROM) for two-phase porous flows. To this end, two projection methods including projecting the original governing equations (Method I) and projecting the discrete form of original governing equations (Method II) are respectively applied to construct the POD-ROM, and their distinctions are compared and analyzed in detail. It is found the POD-ROM established by Method I is inapplicable to multiphase porous flows due to its failed introduction of fluid saturation and permeability that locate on the edge of grid cell, which would lead to unphysical results.

Findings

By using Method II, an efficient IMPES algorithm that can substantially speed up the simulation of two-phase porous flows is developed based on the POD-ROM. The computational efficiency and numerical accuracy of the proposed algorithm are validated through three numerical examples, and simulation results illustrate that the proposed algorithm displays satisfactory computational speed-up (one to two orders of magnitude) without sacrificing numerical accuracy obviously when comparing to the standard IMPES algorithm that without any acceleration technique. In addition, the determination of POD modes number, the relative errors of wetting phase pressure and saturation, and the influence of POD modes number on the overall performances of the proposed algorithm, are investigated.

Originality/value

1. Two projection methods are applied to establish the POD-ROM for two-phase porous flows and their distinctions are analyzed. The reason why POD-ROM is difficult to be applied to multiphase porous flows is clarified firstly in this study. 2. A highly efficient IMPES algorithm based on the POD-ROM is proposed to accelerate the simulation of two-phase porous flows. 3. Satisfactory computational speed-up (one to two orders of magnitude) and prediction accuracy of the proposed algorithm are observed under different conditions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 11
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 1 November 1996

J.P. Bardet

Investigates the effects of two‐phase instability on finite element (FE) solutions for porous hypoelastic solids saturated with an insterstitial fluid. Demonstrates that…

Abstract

Investigates the effects of two‐phase instability on finite element (FE) solutions for porous hypoelastic solids saturated with an insterstitial fluid. Demonstrates that two‐phase instability creates definite problems to the FE computations of coupled solid‐fluid systems. The eigenvectors of the tangential finite element matrices which are responsible for problems are not artificial, but are the bifurcating modes of physical solutions. The investigation, although limited to the plane strain undrained compression of hypoelastic models, is relevant to the investigation of the two‐phase instability of other materials and boundary value problems, and may lead towards an explanation for numerical problems in soil liquefaction analysis.

Details

Engineering Computations, vol. 13 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 28 October 2013

Cheng Cheng and Xiaobing Zhang

In computational fluid dynamics for two-phase reactive flow of interior ballistic, the conventional schemes (MacCormack method, etc.) are known to introduce unphysical…

Abstract

Purpose

In computational fluid dynamics for two-phase reactive flow of interior ballistic, the conventional schemes (MacCormack method, etc.) are known to introduce unphysical oscillations in the region where the gradient is high. This paper aims to improve the ability to capture the complex shock wave during the interior ballistic cycle.

Design/methodology/approach

A two-phase flow model is established to describe the complex physical process based on a modified two-fluid theory. The solution of model is obtained including the following key methods: an approximate Riemann solver to construct upwind fluxes, the MUSCL extension to achieve high-order accuracy, a splitting approach to solve source terms, a self-adapting method to expand the computational domain for projectile motion and a control volume conservation method for the moving boundary.

Findings

The paper is devoted to applying a high-resolution numerical method to simulate a transient two-phase reactive flow with moving boundary in guns. Several verification tests demonstrate the accuracy and reliability of this approach. Simulation of two-phase reaction flow with a projectile motion in a large-caliber gun shows an excellent agreement between numerical simulation and experimental measurements.

Practical implications

This paper has implications for improving the ability to capture the complex physics phenomena of two-phase flow during interior ballistic cycle and predict the combustion details, such as the flame spreading, the formation of pressure waves and so on.

Originality/value

This approach is reliable as a prediction tool for the understanding of the physical phenomenon and can therefore be used as an assessment tool for future interior ballistics studies.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 23 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of over 7000