Fully developed and transient concentration profiles of particulate suspensions sheared in a cylindrical Couette cell

We experimentally investigate particle migration in a non-Brownian suspension sheared in a Taylor–Couette configuration and in the limit of vanishing Reynolds number. Highly resolved index-matching techniques are used to measure the local particulate volume fraction. In this wide-gap Taylor–Couette configuration, we find that for a large range of bulk volume fraction, $\unicode[STIX]{x1D719}_{b}\in [20\,\%{-}50\,\%]$, the fully developed concentration profiles are well predicted by the suspension balance model of Nott & Brady (J. Fluid Mech., vol. 275, 1994, pp. 157–199). Moreover, we provide systematic measurements of the migration strain scale and of the migration amplitude which highlight the limits of the suspension balance model predictions.

Jet Impingement Heat Transfer Using Air-Laden Nanoparticles With Encapsulated Phase Change Materials

Nanoparticles made of polymer encapsulated phase change materials (PCM) are added in air to enhance the heat transfer performance of air jet impingement flows applied to cooling processes. Encapsulation prevents agglomeration of the PCM (paraffin) nanoparticles when they are in the liquid phase. The sizes of the particles are chosen to be small enough so that they maintain near velocity equilibrium with the air stream. Small solid paraffin particles can absorb a significant amount of energy rapidly from a heat source by changing phase from solid to liquid. Nanoparticle volume fraction is found to play an important role in determining the overall pressure drop and heat transfer of the jet impingement process. Specifically, air jets laden with 2.5% particulate volume fraction were shown to improve the average heat transfer coefficient by 58 times in the air flow speed range of 4.6 to 15.2 m/s when compared to that of pure air alone. In addition, the structural integrity of the encapsulating shells was demonstrated to be excellent by the repeated use of the nanoparticles in closed loop testing.

Study of Particle Distribution in Al-SiC Particulate Composite by Random Motion of Mould

Synthesis of Al metal matrix composites (MMCs) with ceramic particulate reinforcements through casting route is associated with the problem of non-uniform distribution of particulate. The problem of non-uniform distribution is more for the case of larger particulate volume fraction. In the present study a novel method has been tried to overcome this. It involves random movement of mold containing liquid aluminium and ceramic particulates ieSiC. In the present studythe spherical mold containing molten aluminium and SiC particulates of size 50-100µm is allowed to rotate in a cylindrical drum to impart a random rotation as well translation Before the design of experiment the process simulation has already been done. Accordingly the process has been fabricated. At present the process is a crude one. Preliminary experiments show that the distributions of particles obtained by this technique are better as compared to that of stir cast composites with similar volume fraction of reinforcement. However, the result obtained by the novel technique varied as proper control over the random motion of the mold was not possible. Although uniform microstructure could be obtained in most of the experiment in some cases and certain zones the microstructure showed a non uniform distribution of particles. The temperature of mold before it is subjected to random movement is strongly influenced the particle distribution.

Microstructure and Mechanical Properties of In Situ TiB2/6061 Composites

In situ TiB2/6061 composites have been successfully synthesized through chemical reaction between 6061 master alloy, Al-3B master alloy and Ti powder. The composites fabricated by direct melt mixing method was investigated by Scanning Electron Microscope (SEM), Energy Dispersive x-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD), The results shown the existence of TiB2particles. The size of most TiB2particles were just in micron level, and even reached to sub-micron level. The increase in microhardness and tensile strength for the as-prepared composites with 5% particulate volume fraction (PVF) are up to 26.8% and 51.2% respectively.

The Influence of Interfacial and Structural Parameters on the Elastic Modulus of SiCp/6066Al Composites

The effects of the interfacial parameters (interface/matrix modulus ratio, interface Poisson ratio and interface volume fraction) and the structural parameters (particulate volume fraction, particulate shape, arrangement pattern and dimensional variance mode) on the elastic modulus of SiCp/6066Al composites were calculated and analyzed. The results showed that component and interface performance significantly influenced the elastic modulus of the composite; but the particulate shape, arrangement pattern and dimensional variance mode were found to have little influence. This means that the effect of the above structural parameters can be negligible. The optimal approach to enhance the elastic modulus and specific elongation of a composite is to improve the interfacial bonding of the particulate. Optimal results are obtained when the interface modulus is 20% ~ 30% of the matrix modulus.