Investigation of the stability of a plane-channel suspension flow with account for finite particle volume fraction

2008 ◽  
Vol 43 (6) ◽  
pp. 873-884 ◽  
Author(s):  
S. A. Boronin
Keyword(s):  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Plane Channel ◽  
Suspension Flow ◽  
Particle Volume ◽  
The Stability ◽  
Finite Particle

On the stability of plane-parallel dusty-gas flows

2007 ◽  
Vol 5 ◽  
pp. 121-126
Author(s):  
S.A. Boronin
Keyword(s):  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Plane Channel ◽  
Momentum Exchange ◽  
Two Phase Flows ◽  
Particle Volume ◽  
Two Phase ◽  
Stability Margins ◽  
Plane Parallel ◽  
The Stability

In the framework of two-fluid approach, we consider different formulations of the stability of plane-parallel two-phase flows. New factors are taken into account, namely, non-uniform particle concentration and particle velocity slip in the main flow, Saffman lift force in the interphase momentum exchange and a finite particle volume fraction. The study is aimed at the analysis of the effect of these factors on the critical Reynolds number and the stability margins of two-phase flows in a plane channel and boundary layer.

Existence and uniqueness of normal shock waves in gas-particle mixtures

1969 ◽  
Vol 38 (3) ◽  
pp. 633-655 ◽  
Author(s):  
Barbara Schmitt-Von Schubert
Keyword(s):  
Shock Waves ◽  
Existence And Uniqueness ◽  
Constant Velocity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Solid Particles ◽  
Equilibrium Flow ◽  
Particle Volume ◽  
Flow Parameters ◽  
Finite Particle

A mixture of a gas and small solid particles is considered which, far upstream, is in a constant equilibrium state, and moves with a constant velocity. The existence of shock waves is investigated in the four possible cases, namely for frozen flow, for two kinds of partly frozen flow, and for equilibrium flow. It is shown that, in all these cases, compressive shocks may exist, if the upstream velocity exceeds the velocity of sound appropriate to the type of flow. Rarefaction shocks are impossible in each case. Moreover, it is shown that the downstream values of the flow parameters are determined uniquely, and the direction of their change is given. Only rather general assumptions concerning the behaviour of the gas are needed. The paper takes into account the influence of the finite particle volume fraction unlike most previous papers on the topic.

Parametric Study for the Phase-Change Process of Liquid Flow With Microencapsulated PCM Particles in Microchannels

2007 ◽  
Author(s):  
Yingli Hao ◽  
Jinli Lu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Wall Temperature ◽  
Change Process ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Suspension Flow ◽  
Particle Volume ◽  
Constant Wall Temperature ◽  
Phase Change Process

The phase-change process of phase-change material (PCM) is the key for the microencapsulated phase-change material (MCPCM) particle suspension flow to enhance the heat transfer, enlarge the capability of thermal energy transportation and employ in the engineering application. In the present paper, the parametric study for the phase-change process of the MCPCM suspension flow in a heated microchannel is carried out using the model and numerical technique developed in previous works. The effects of particle volume fraction, Reynolds number, and wall heat flux on the phase-change process have been numerically analyzed. It is found that the benefits of enhancing heat transfer and reducing wall temperature by employing the MCPCM particle are limited to the melting region. There exists a constant wall temperature region in the melting region under the certain condition. The trend of influence of particle volume fraction, Reynolds number, and wall heat flux on starting location, length, wall temperature, and average heat transfer coefficient in the constant wall temperature region is revealed. The numerical simulation may guide the optimal condition of design and operation to utilize the MCPCM suspension flow not only for enhancing the convection heat transfer and enlarging the thermal energy transportation capability, but also for controlling the micro-device temperature uniform.

Self-propulsion and dispersion of reactive colloids due to entropic anisotropy

2010 ◽  
Vol 657 ◽  
pp. 64-88 ◽  
Author(s):  
HSIEN-HUNG WEI ◽  
JENG-SHIUNG JAN
Keyword(s):  
Volume Fraction ◽  
Rotational Symmetry ◽  
Particle Volume Fraction ◽  
Solute Concentration ◽  
Dlvo Theory ◽  
Particle Volume ◽  
Simple Scaling ◽  
Reactive Solutes ◽  
The Stability ◽  
Self Motion

In this paper, self-motion of reactive colloids and their dispersion behaviour are theoretically examined. The motion is driven by an osmotic force imbalance arising from non-uniform atmospheres of reactive solutes around the colloids. The propulsion here is not limited to Janus-like particles. It can also occur to particles having ‘uniform’ reactivity due to the more universal mechanism – entropic anisotropy created by breaking in rotational symmetry. The idea is demonstrated by examining the motion of a reactive particle due to asymmetry in its shape or to the presence of an additional particle. In the two-particle problem, in particular, we find that sink (source) particles can self-migrate towards (apart from) each other at velocities varying as R−2, resembling Coulomb attraction (repulsion), where R is the inter-particle distance. Because of this Coulomb-like nature, a suspension of sink particles could undergo collective flocculation due to unscreened osmotic attraction. The criterion for an occurrence of the flocculation is also established. It reveals that the flocculation can occur if the particle volume fraction is within a certain window in terms of the solute concentration and the particle reactivity. The stability of reactive suspensions is also discussed using the modified Derjaguin–Landau–Verwey–Overbeek (DLVO) theory that takes account of the competition between long-range reaction-induced osmotic forces and short-range colloidal forces. A more generalized view for the present self-driven particle motion is elucidated by a simple scaling theory, providing lucid accounts for the self-motion of two particles, composite bodies, and Janus particles – all are driven by dipolar distortions in potential energy. Comparison with phoretic self-swimmers is also discussed.

scholarly journals Performance improvement of double-tube gas cooler in CO2 refrigeration system using nanofluids

2015 ◽  
Vol 19 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Jahar Sarkar
Keyword(s):  
Performance Improvement ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Cooling Capacity ◽  
Inlet Temperature ◽  
Refrigeration Cycle ◽  
Particle Volume ◽  
Transcritical Carbon Dioxide ◽  
The Given ◽  
Theoretical Analyses

The theoretical analyses of the double-tube gas cooler in transcritical carbon dioxide refrigeration cycle have been performed to study the performance improvement of gas cooler as well as CO2 cycle using Al2O3, TiO2, CuO and Cu nanofluids as coolants. Effects of various operating parameters (nanofluid inlet temperature and mass flow rate, CO2 pressure and particle volume fraction) are studied as well. Use of nanofluid as coolant in double-tube gas cooler of CO2 cycle improves the gas cooler effectiveness, cooling capacity and COP without penalty of pumping power. The CO2 cycle yields best performance using Al2O3-H2O as a coolant in double-tube gas cooler followed by TiO2-H2O, CuO-H2O and Cu-H2O. The maximum cooling COP improvement of transcritical CO2 cycle for Al2O3-H2O is 25.4%, whereas that for TiO2-H2O is 23.8%, for CuO-H2O is 20.2% and for Cu-H2O is 16.2% for the given ranges of study. Study shows that the nanofluid may effectively use as coolant in double-tube gas cooler to improve the performance of transcritical CO2 refrigeration cycle.

A simulation and experimental study on particle volume fraction of PMMA suspension in centrifugal fields

2021 ◽  
Author(s):  
Yosephus Ardean Kurnianto Prayitno ◽  
Tong Zhao ◽  
Yoshiyuki Iso ◽  
Masahiro Takei
Keyword(s):  
Experimental Study ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume

Solidification Processing of Functionally Graded Materials by Sedimentation

1999 ◽  
Author(s):  
J. W. Gao ◽  
S. J. White ◽  
C. Y. Wang
Keyword(s):  
Functionally Graded Materials ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Computer Code ◽  
Functionally Graded ◽  
Particle Volume ◽  
Particle Sedimentation ◽  
Graded Materials ◽  
Free Zone ◽  
Free Region

Abstract A combined experimental and numerical investigation of the solidification process during gravity casting of functionally graded materials (FGMs) is conducted. Focus is placed on the interplay between the freezing front propagation and particle sedimentation. Experiments were performed in a rectangular ingot using pure substances as the matrix and glass beads as the particle phase. The time evolutions of local particle volume fractions were measured by bifurcated fiber optical probes working in the reflection mode. The effects of various processing parameters were explored. It is found that there exists a particle-free zone in the top portion of the solidified ingot, followed by a graded particle distribution region towards the bottom. Higher superheat results in slower solidification and hence a thicker particle-free zone and a higher particle concentration near the bottom. The higher initial particle volume fraction leads to a thinner particle-free region. Lower cooling temperatures suppress particle settling. A one-dimensional solidification model was also developed, and the model equations were solved numerically using a fixed-grid, finite-volume method. The model was then validated against the experimental results, and the validated computer code was used as a tool for efficient computational prototyping of an Al/SiC FGM.

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