Investigation on Phase Change Behavior of Paraffin Phase Change Material in a Spherical Capsule for Solar Thermal Storage Units

In this work, the melting and solidification behaviour of paraffin phase change material encapsulated in a stainless steel spherical container has been studied experimentally. A computational fluid dynamics analysis has also been performed for the encapsulated phase change material (PCM) during phase change process. In the melting process, the hot air, used as the heat transfer fluid enters the test section and flows over the spherical capsule resulting in the melting of phase change material. In the solidification process, the ambient air flows over the capsule and received heat from phase change material resulting in the solidification of phase change material. In the computational fluid dynamics, the constant wall boundary condition is employed for both melting (75°C) and solidification (36°C) processes since the internal conductive resistance offered by the PCM is much higher compared to the outer surface convective resistance. The time required for complete solidification and melting of the phase change material obtained from the computational fluid dynamics analysis are validated with the experimental results and a reasonable agreement is achieved. The reason for the deviation between the results are analyzed and reported.     

Synthesis of MoS2 nanoparticle deposited graphene/mesoporous MnOx nanocomposite for high performance super capacitor application

The present study deal with the fabrication of low cost nanocomposite based electrodes based on Nickel foam binder free substrate for supercapacitor applications. The composition of nanocomposite is molybdenum sulphide nanoparticle/graphene coated on mesoporous manganese oxide. The first step is to involve the preparation of mesoporous manganese oxide by non-ionic surfactant assisted method. In the second stage is to deposit the reduced graphene on mesoporous manganese oxide in the presence of ultrasonic irradiation followed by addition of known quantity of commercial MoS₂ nanopowder (particle size below 90 nm). The manganese oxide based nanocomposite is showing porous architecture with graphene sheet formation together with MoS₂ nanoparticle deposition. N₂ adsorption-desorption Isotherm curves for MoS₂ nanoparticle (NP) modified graphene oxide/meso-MnO₂ and pure meso-MnO₂ displayed type IV isotherm with improved surface area values. The reduced graphene oxide (graphene) and MoS₂ exist in the form of glassy flaky morphology as well as tubular/needle shapes are obtained after the deposition process in the final nanocomposite. The orderly arranged and anchored nano-sized mesoporous manganese oxide nanocomposites are showed increased specific capacitance (up to 527, 727 and 1160 F/g) and continuous cyclic stability.     

Modelling Corrosion Behavior of Friction Stir Processed Aluminium Alloy 5083 Using Polynomial: Radial Basis Function

Aluminium alloy 5083, widely used in marine applications, undergoes accelerated corrosion in sea water due to the aggressive reaction of chloride ions with the secondary phase particles and other intermetallics present in the alloy matrix. The corrosion rate of the alloy is also influenced by the temperature difference between the alloy and its environment. Friction stir processing (FSP) is a recent solid state processing technique for improving the surface properties of metals and alloys. In this study, an attempt has been made to explore the possibility of improving the corrosion resistance of AA5083 by FSP. FSP trials were performed by varying the tool rotation speed, tool traverse speed and shoulder diameter of the tool, as per face centered central composite design. The corrosion potential and the corrosion rate of friction stir processed AA5083 was studied using potentiodynamic polarization studies, at three different temperatures. Mathematical models based on polynomial—radial basis function were developed and used to study the effect of process parameters on the corrosion potential and the corrosion rate of friction stir processed AA5083. FSP resulted in refinement of the grain structure, dispersion and partial dissolution of secondary phase particles in the matrix, which increased the corrosion resistance of the alloy.     

Analysis of Metallurgical and Mechanical Properties of Continuous and Pulsed Current Gas Tungsten Arc Welded Alloy C-276 with Duplex Stainless Steel

The present work investigates the microstructure and mechanical properties of alloy C-276 fabricated by continuous and pulsed current gas tungsten arc welding process and by employing ER2553 filler wire. Optical and scanning electron microscopic analyses were carried out to study the microstructures of weldments produced. Energy dispersive X-ray spectroscopy (EDS) was performed to investigate the formation of secondary phases in the weldments. The results disclosed that pulsed current gas tungsten arc welding showed refined microstructure compared to continuous current gas tungsten arc welding. SEM/EDS analysis revealed the segregation of Mo in the weld interface regions in both the welding techniques. The extent of microsegregation reduced the strength and toughness of the weld joint compared to the base metal. Bend test revealed cracks in the weld interface region in both the weldments.     

Spectral and laser studies on energy transfer binary dye-doped polymer laser rods

The energy transfer mechanism of two different dyes, C450 as donor and C535 as acceptor incorporated into polymeric matrices, is investigated. The absorption and fluorescence characteristics of C450 and C535 dye-doped polymer modified with ethanol are studied. The results are compared with their respective liquid mixtures. The spectral parameters of C450 and C535 in polymer and the corresponding monomer compositions are obtained. We study the variation of gain for different acceptor concentrations whilst keeping the donor concentration fixed. The gain of acceptor with donor increased and then decreased as the acceptor concentration was increased. Both solid and liquid media showed similar trends. We also study the photobleaching of the dye-doped polymer rod under nitrogen laser excitation.     

Copper Complex of Aminoisoborneol Schiff Base Cu2(SBAIB‐d)2: An Efficient Catalyst for Direct Catalytic Asymmetric Nitroaldol (Henry) Reaction

A new bifunctional copper complex of the aminoisoborneol Schiff base – Cu₂(SBAIB‐d)₂ – has been developed for the effective direct catalytic asymmetric Henry reaction. One mol% of this catalyst produces the expected Henry products in high yields (up to 99%) with excellent enantioselectivities (up to 98% ee). The utility of the present catalyst was also extended to the Henry reaction with nitroethane and 1‐nitropropane that furnished the corresponding products in moderate to high yields (up to 99%) with moderate to high enantioselectivities of syn (up to 98% ee) and anti (up to 98% ee) diastereomers. The highlights of this catalytic system are easy manipulation, air and moisture tolerance, the need for 1 mol% of an easily synthesizable catalyst and the high enantioselectivities achieved for a wide range of substrates.     

Monitoring of hard turning using acoustic emission signal

Monitoring of tool wear during hard turning is essential. Many investigators have analyzed the acoustic emission (AE) signals generated during machining to understand the metal cutting process and for monitoring tool wear and failure. In the current study on hard turning, the skew and kurtosis parameters of the root mean square values of AE signal (AERMS) are used to monitor tool wear. The rubbing between the tool and the workpiece increases as the tool wear crosses a threshold, thereby shifting the mass of AERMS distribution to right, leading to a negative skew. The increased rubbing also led to a high kurtosis value in the AERMS distribution curve.     

Adsorption equilibrium,thermodynamics, kinetics,mechanism and process design of zinc(II) ions onto cashew nut shell

Cashew nut shell (CNS) is an agricultural waste was investigated as a new adsorbent for the removal of zinc(II) from aqueous environment. Effects of solution pH, CNS dose, contact time, initial zinc(II) concentration and temperature on removal efficiency were tested and optimum conditions were evaluated. The equilibrium data were fitted well with Langmuir isotherm model and pseudo‐second‐order kinetic model. Langmuir monolayer adsorption capacity of CNS was examined as 24.98 mg/g. Changes in standard Gibbs free energy (?G°), standard enthalpy (?H°) and standard entropy (?S°) showed that the sorption of zinc(II) ions onto CNS are spontaneous and exothermic at 303–333 K. Sorption process was found to be controlled by both surface and pore diffusion. A batch adsorber was designed for different CNS dose to effluent volume ratios using Langmuir equation. Effective diffusivity values were found to be 1.927 × 10^?11 (10 mg/L), 2.135 × 10^?11 (20 mg/L), 2.267 × 10^?11 (30 mg/L), 2.305 × 10^?11 (40 mg/L) and 2.362 × 10^?11 (50 mg/L) m²/s. © 2011 Canadian Society for Chemical Engineering