Constructal Design of Particle Volume Fraction in Nanofluids

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Chao Bai ◽  
Liqiu Wang
Keyword(s):  
Thermal Resistance ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Circular Disk ◽  
Small Scale ◽  
Particle Volume ◽  
Constructal Design ◽  
Dispersed Particles ◽  
Overall Resistance ◽  
Plane Slab

Abstract We perform a constructal design of particle volume fraction of four types of nanofluids used for heat conduction in four systems: a circular disk, a sphere, a plane slab, and a circular annulus. The constructal volume fraction is obtained to minimize system overall temperature difference and overall thermal resistance. Also included are the features of the constructal volume fraction and the corresponding constructal thermal resistance, which is the minimal overall resistance to the heat flow. The constructal nanofluids that maximize the system performance are not necessarily the ones with uniformly dispersed particles in base fluids. Nanofluids research and development should thus focus on not only nanofluids but also systems that use them. The march toward micro- and nanoscales must also be with the sobering reminder that useful devices are always macroscopic, and that larger and larger numbers of small-scale components must be assembled and connected by flows that keep them alive.

CONSTRUCTAL DESIGN OF NANOFLUIDS FOR ONE-DIMENSIONAL STEADY HEAT CONDUCTION SYSTEMS

NANO ◽  
2010 ◽  
Vol 05 (01) ◽  
pp. 39-51 ◽  
Author(s):  
CHAO BAI ◽  
LI QIU WANG
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Thermal Resistance ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume ◽  
Constructal Design ◽  
Dispersed Particles ◽  
Steady Heat Conduction ◽  
Steady Heat

We perform a constructal design of nanofluid particle volume fraction for four heat-conduction systems and four types of nanofluids to address whether nanofluids with uniformly-dispersed particles always offer the optimal global performance. The constructal volume fraction is obtained to minimize the system overall temperature difference and overall thermal resistance. The constructal thermal resistance is an overall property fixed only by the system global geometry and the average thermal conductivity of nanofluids used in the system. Efforts to enhance the thermal conductivity of nanofluids are important to reduce the constructal overall thermal resistance. The constructal nanofluids that maximize the system performance depend on both the type of nanofluids and the system configuration, and are always having a nonuniform particle volume fraction for all the cases studied in the present work. Nanofluids research and development should thus focus on not only nanofluids but also systems that use them.

scholarly journals Parameters in Multiphase Flowing of Natural Gas NGH Slurry via Vertical Pipe

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Dai Maolin ◽  
Wu Kaisong
Keyword(s):  
Pressure Drop ◽  
Natural Gas ◽  
Simulation Model ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Solid Particles ◽  
Small Scale ◽  
Vertical Pipe ◽  
Particle Volume ◽  
The Relationship

In recent years, the pipeline flowing of natural gas hydrate (hereinafter NGH) slurry has been a promising technique of multiphase flowing via pipe and that of crushed hydrate mixture slurry is also a key technique in solid fluidization mining method of nondiagenetic NGH reservoir below the seabed. In this paper, by using similarity rules, a small-scale simulation model was established to shorten the calculation time. The correctness of the simulation model has been verified through comparison with experiment. Thereby, the distribution of velocity and volume fraction of each phase in the vertical pipe was obtained, and the prototype of vertical pipe was analyzed. By study on the pipe resistance, the pressure drop of slurry, when flowing in vertical pipe, could be calculated asΔP=ρgh+0.23Cρv1.8. In the end, by adjusting volume fraction of particles in the mixture slurry, the relationship between the solid particles’ volume fraction and piezometric pressure drop was obtained. When the optimal flow velocity of the slurry is 2 m/s and the ratio of NGH volume fraction to that of sand is 4 : 1, the optimal particle volume fraction ranges from 20% to 40%.

Rheological Study of Micro Particle Laden Polymeric Thermal Interface Materials: Part 2 — Modeling

2002 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-Lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Yield Stress ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Complete Set ◽  
Interface Materials

Currently there are no models to predict the thickness or the bondline thickness (BLT) of particle laden polymeric thermal interface materials (TIM) for parameters such as particle volume fraction and pressure. TIMs are used to reduce the thermal resistance. Typically this is achieved by increasing the thermal conductivity of these TIMs by increasing the particle volume fraction, however increasing the particle volume fraction also increases the BLT. Therefore, increasing the particle volume fraction may lead to an increase in the thermal resistance after certain volume fraction. This paper introduces a model for the prediction of the BLT of these particle laden TIMs. Currently thermal conductivity is the only metric for differentiating one TIM formulation from another. The model developed in this paper introduces another metric: the yield stress of these TIMs. Thermal conductivity and the yield stress together constitute the complete set of material parameters needed to define the thermal performance of particle laden TIMs.

Spin-up from rest of a mixture: numerical simulation and asymptotic theory

1993 ◽  
Vol 246 ◽  
pp. 443-464 ◽  
Author(s):  
Gustav Amberg ◽  
Marius Ungarish
Keyword(s):  
Asymptotic Theory ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Fluid Motion ◽  
Particle Volume ◽  
Solid Body Rotation ◽  
Dispersed Particles ◽  
Model Equations ◽  
Shaped Domain ◽  
Good Agreement

Spin-up from rest of a separating fluid–particle mixture is studied. A cylindrical container, filled with a stationary mixture of initially uniform particle volume fraction, is instantaneously set into rapid rotation. The viscous forces.on the walls introduce a secondary Ekman-layer circulation which causes the fluid motion to gradually approach a state of solid-body rotation. While the mixture acquires angular momentum, separation starts under the action of the local centrifugal effects: the dispersed particles – assumed here to be lighter than the fluid – tend to concentrate around the centre, leaving behind a peculiarly shaped domain of pure fluid. This process is simulated by a finite difference version of the ‘mixture model’ equations. The numerical results are in good agreement with previous asymptotical predictions but also illuminate some aspects of the flow field that have been covered by the analytical approach.

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
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