Melting of NEPCM within a Cylindrical Tube: Numerical Study Using the Lattice Boltzmann Method

This article presents a numerical investigation on melting of phase change material (PCM) enhanced by nanoparticles inside a cylindrical tube using the lattice Boltzmann method. Water (ice) and copper particles are chosen as the base fluid (PCM) and nanoparticles, respectively. Results show that the melting rate is the same for all regions of the cylinder for a low Rayleigh number, while it intensifies at the top half of the cylinder for a moderate Rayleigh number. Also, existence of strong unstable flow in the bottom portion of the cylinder at a Rayleigh number of 10⁶ causes the melting rate to keen after a definite time. Nanoparticles have no significant effect on the melting rate at the beginning of melting, where the conduction mode of heat transfer dominates between the hot wall and solid PCM, while full melting of PCM occurs earlier by the increase of solid concentration.     

Surface integrity in broaching of AA 7075-T651 aluminum alloys

Special features as noncircular hole shapes are manufactured by the broaching process. The rise per tooth varies in different zones of the broaching tool. In this article, the effects of the two main process parameters (cutting speed and rise per tooth) on surface integrity (surface roughness, micro-hardness) and chip morphology will be studied. The experiments have been done on AA7075-T651 aluminum alloy. To investigate the effect of rise per tooth, one of the cutting edges of broaching tool is separated and the broaching process is implemented for nine samples. The samples are broached with three different cutting speeds (6, 12 and 18 m/min) and three rise per tooth (0.02, 0.05 and 0.1?mm). Also, the effect of cutting speed is investigated with a broaching needle (rise per tooth 0.1?mm). The results show that best surface roughness is obtained at cutting speed 12 m/min. The surface roughness will be improved by decreasing the rise per tooth. Also, the surface hardness decreases by increasing the cutting speed. The surface integrity (surface roughness and surface hardness) is comparable for single edge cutting tool and broaching needle. Continuous chips are formed during the broaching process and decreasing the cutting speed cause more compression of the chips.     

The effect of nitric acid,ethylenediamine, and diethanolamine modified polyaniline nanoparticles anode electrode in a microbial fuel cell

Anode materials are important in the power generation of microbial fuel cell. In this study, polyaniline was used as a conducting polymer anode in two chambers MFC. XPS and SEM were used for the characterization of functional groups of anode materials and the morphology. The power generation of microbial fuel cell was elevated by the modification of anode by nitric acid, ethylenediamine, and diethanolamine. The time that MFC reaches its maximum power generation was shortened by modification. Moreover the SEM photos prove that, it causes better attachment of microorganisms as biocatalysts on electrode surface. The best performance of among the MFCs with different anode electrodes, was the system working by polyaniline modified by ethylenediamine as that generated power of 136.2 mW/m² with a 21.3% Coulombic efficiency.