Two-phase and single phase models of flow of nanofluid in a square cavity: Comparison with experimental results

2016 ◽  
Vol 100 ◽  
pp. 372-380 ◽  
Author(s):  
M. Ziad Saghir ◽  
Amirhossein Ahadi ◽  
Tooraj Yousefi ◽  
Bahram Farahbakhsh
Keyword(s):  
Single Phase ◽  
Experimental Results ◽  
Square Cavity ◽  
Two Phase ◽  
Phase Models

Parametric Analysis of Single-Phase and Two-Phase Models of a Microfluidic Direct Methanol Fuel Cell

2013 ◽  
Author(s):  
Usama Tohid ◽  
Arturo Pacheco-Vega
Keyword(s):  
Fuel Cell ◽  
Parametric Analysis ◽  
Single Phase ◽  
Operating Conditions ◽  
Cell Performance ◽  
Geometrical Parameters ◽  
Two Phase ◽  
Flow Rates ◽  
Direct Methanol ◽  
Phase Models

We perform numerical simulations of single-phase and two-phase models of a direct methanol microfluidic fuel cell (μ-DMFC). The focus of this study is on the parametric analysis of a single channel of the system, for specific sets of operating conditions, in order to map the dependence of the cell performance with respect to the geometrical parameters. Different geometries, ranging from 500 μm to 4 mm in width, and 500 μm to 4 cm in length, along with membrane thicknesses from 50 μm to 500 μm, were considered. The mathematical models are given in terms of the Navier-Stokes, the Butler-Volmer and the Maxwell-Stefan equations, along with Darcy’s equation for the flow across the membrane. The difference between the single- and two-phase flow models lies upon the specific constitutive equations used. For each geometry and operating condition, the two-dimensional equations were solved by a finite element method. The conditions of operation include: flow rates and inlet weight fractions of methanol at the anode and oxygen the cathode. The results from this analysis, presented as polarization curves and power densities, indicate that fuel-cell systems with higher flow rates and inlet weight fraction of methanol achieve the best performance. However, when the concentration of methanol exceeds 2M the cell performance is negatively impacted due to crossover. Comparison of the results indicates that the two-phase model has a more restrictive domain for both the geometrical parameters and operating conditions.

Comparison of Single and Two-Phase Models for the Study of Mixed Convection Flows With Nanofluids

2010 ◽  
Author(s):  
Mahmood Akbari ◽  
Amin Behzadmehr ◽  
Nicolas Galanis
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mixed Convection ◽  
Single Phase ◽  
Volume Fraction ◽  
Solid Particles ◽  
Two Phase ◽  
Prediction Ability ◽  
Numerical Predictions ◽  
Phase Models

The single phase and three different two phase models (Volume of fluid, Mixture and Eulerian) are used to analyse laminar mixed convection flow of Al2O3-water nanofluids in a horizontal tube, in order to evaluate their prediction ability. The flow is considered steady and developing. The fluid’s physical properties are temperature dependent whereas those of the solid particles are constant. A uniform heat flux is applied at the fluid-solid interface. Two different Reynolds numbers and three different volume fractions have been considered. The governing three-dimensional partial differential equations are elliptical in all directions and coupled. Predicted convective heat transfer coefficients, velocity, and temperature profiles, as well as secondary flow’s velocity vectors and temperature contours are compared at different axial positions. To validate the comparisons and verify the accuracy of the results, the numerical predictions are compared with corresponding experimental data. There are essentially no differences between the predictions of the two-phase models; however their results are significantly different from those of the single-phase approach. Two-phase model results are closer to the experimental data, but they show an unrealistic increase in heat transfer for small changes of the particle volume fraction. Hydrodynamically, the two-phase and single-phase approaches perform almost the same but their thermal predictions are quite different.

Modeling of Carbon Dioxide Formation in Flowing Electrolyte-Direct Methanol Fuel Cells

2011 ◽  
Author(s):  
David Ouellette ◽  
C. Ozgur Colpan ◽  
Edgar Matida ◽  
Cynthia A. Cruickshank
Keyword(s):  
Fuel Cell ◽  
Direct Methanol Fuel Cell ◽  
Single Phase ◽  
Direct Methanol Fuel Cells ◽  
Phase Model ◽  
Two Phase ◽  
One Dimensional ◽  
Direct Methanol ◽  
Phase Models ◽  
Methanol Fuel Cell

A one-dimensional two-phase model has been developed for a direct methanol fuel cell (DMFC) and flowing electrolyte - direct methanol fuel cell (FE-DMFC). The model has been compared to experimental data found in literature and corresponds well. Using this model, the performance of the DMFC and FE-DMFC are evaluated and compared to one another as well as to their respective single phase models. It has been found that there is a substantial difference between a two-phase and single phase model. Furthermore, the FE-DMFC outperformed the DMFC when it came to methanol inlet concentrations and varying operating temperatures due to the FE-DMFC’s ability to reduce the methanol crossover.

scholarly journals Comparative numerical study of single and two-phase models of nanofluid liquid film evaporation in a vertical channel

2020 ◽  
Vol 307 ◽  
pp. 01034 ◽  
Author(s):  
Monssif Najim ◽  
M’barek Feddaoui ◽  
Abderrahman Nait Alla ◽  
Adil Charef
Keyword(s):  
Mass Transfer ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Liquid Film ◽  
Heat And Mass Transfer ◽  
Difference Method ◽  
Single Phase ◽  
Vertical Channel ◽  
Two Phase ◽  
Phase Models

The main purpose of this study is to survey numerically comparison of two-phase and single-phase models of heat and mass transfer of Al2O3-water nanofluid liquid film flowing downward a vertical channel. A finite difference method is developed to produce the computational predictions for heat and mass transfer during the evaporation of the liquid film approached by the single-phase and two-phase models. The model solves the coupled governing equations in both nanofluid and gas phases together with the boundary and interfacial conditions. The systems of equations obtained by using an implicit finite difference method are solved by Tridiagonal Matrix Algorithm. The results show that the two-phase model is more realistic since it takes into account the thermophoresis and Brownian effects.

The Two-Phase Critical Flow of One-Component Mixtures in Nozzles, Orifices, and Short Tubes

1971 ◽  
Vol 93 (2) ◽  
pp. 179-187 ◽  
Author(s):  
Robert E. Henry ◽  
Hans K. Fauske
Keyword(s):  
Critical Pressure ◽  
Single Phase ◽  
Pressure Ratio ◽  
Stagnation Pressure ◽  
Experimental Results ◽  
Critical Flow ◽  
Two Phase ◽  
Transfer Rates ◽  
Critical Flow Rate ◽  
Flow Through

The critical flow of one-component, two-phase mixtures through convergent nozzles is investigated and discussed including considerations of the interphase heat, mass, and momentum transfer rates. Based on the experimental results of previous investigators, credible assumptions are made to approximate these interphase processes which lead to a transcendental expression for the critical pressure ratio as a function of the stagnation pressure and quality. A solution to this expression also yields a prediction for the critical flow rate. Based on the experimental results of single-phase compressible flow through orifices and short tubes, the two-phase model is extended to include such geometries. The models are compared with steam-water, cryogenic, and alkali-metal experimental data.

Comparisons of single-phase and two-phase models for numerical predictions of Al2O3/water nanofluids convective heat transfer

2020 ◽  
Vol 31 (7) ◽  
pp. 3050-3061
Author(s):  
Zhaoping Ying ◽  
Boshu He ◽  
Di He ◽  
Yucheng Kuang ◽  
Jie Ren ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Single Phase ◽  
Two Phase ◽  
Numerical Predictions ◽  
Phase Models

COMPARATIVE NUMERICAL STUDY OF SINGLE-PHASE AND TWO-PHASE MODELS FOR BIO-NANOFLUID TRANSPORT PHENOMENA

2014 ◽  
Vol 14 (01) ◽  
pp. 1450011 ◽  
Author(s):  
O. ANWAR BÉG ◽  
M. M. RASHIDI ◽  
M. AKBARI ◽  
A. HOSSEINI
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Solid Particles ◽  
Two Phase ◽  
Constant Wall Temperature ◽  
Phase Models

A computational fluid dynamics (CFD) simulation of laminar convection of Al 2 O 3–water bio-nanofluids in a circular tube under constant wall temperature conditions was conducted, employing a single-phase model and three different two-phase models (volume of fluid (VOF), mixture and Eulerian). The steady-state, three-dimensional flow conservation equations were discretised using the finite volume method (FVM). Several parameters such as temperature, flow field, skin friction and heat transfer coefficient were computed. The computations showed that CFD predictions with the three different two-phase models are essentially the same. The CFD simulations also demonstrated that single-phase and two-phase models yield the same results for fluid flow but different results for thermal fields. The two-phase models, however, achieved better correlation with experimental measurements. The simulations further showed that heat transfer coefficient distinctly increases with increasing nanofluid particle concentration. The physical properties of the base fluid were considered to be temperature-dependent, while those of the solid particles were constant. Grid independence tests were also included. The simulations have applications in novel biomedical flow processing systems.

A comparative analysis on the single-phase and two-phase mixture models for calculation of ferrofluid convective heat transfer in the presence of a magnetic field: a numerical study

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hamed Jafari ◽  
Mohammad Goharkhah ◽  
Alireza Mahdavi Nejad
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Single Phase ◽  
Numerical Study ◽  
Phase Method ◽  
Two Phase ◽  
Content Type ◽  
Phase Models

Purpose This paper aims to analyze the accuracy of the single and two-phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field. The findings of current study are compared with previous single-phase numerical results and experimental data. Accordingly, the effect of various parameters including nanoparticles concentration, Reynolds number and magnetic field strength on the performance of the single and two-phase models are evaluated. Design/methodology/approach A two-phase mixture numerical study is carried out to investigate the influence of four U-shaped electromagnets on the hydrodynamic and thermal characteristics of Fe3O4/Water ferrofluid flowing inside a heated channel. Findings It is observed that the applied external magnetic field signifies the convective heat transfer from the channel surface, despite local reduction at a few locations. The maximum heat transfer enhancement is predicted as 23% and 25% using single and two-phase models, respectively. The difference between the results of the two models is mainly attributed to the slip velocity effect which is accounted for in the two-phase model. The magnetic field gradient leads to a significant increase in the slip velocity which in turn causes a slight difference in velocity and temperature profiles obtained by the single and two-phase models in the magnetic field region. According to percentage error calculation, the two-phase method is generally more accurate than the single-phase method. However, the percentage error of both models improves by decreasing either magnetic field intensity or Reynolds number. Originality/value For the first time in the literature, to the best of the authors’ knowledge, the current work analyzes the accuracy of the single and two phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field.

Sign in / Sign up

Export Citation Format

Share Document