CFD study of forced convective heat transfer enhancement in a 90° bend duct of square cross section using nanofluid

In this paper, the forced convective heat transfer enhancement with nanofluids in a 90° pipe bend has been presented. Numerical investigation is carried out for the turbulent flow through the pipe employing finite volume method. The governing differential equations are discretized using hexahedral cells, and the resulting algebraic equations are solved using Commercial solver Fluent 6.3. In order to close the time averaged Navier–Stokes equations, the two-equation k–? turbulence model with a standard wall function have been used. The duct Reynolds number is varied in the range of 2,500–6,000. It is observed that the heat transfer is enhanced significantly by varying the volume fraction of the nanofluid. It is also found that the heat transfer is increased with Reynolds number. A strong secondary flow is observed due to the presence of the wall. Turbulent kinetic energy near outer wall is found to be higher than the inner wall of the bend. A comparative assessment for the heat transfer enhancement with different types of nanofluids is also presented. The computed results of area weighted average Nusselt numbers are validated with some of the existing literature.     

Optimization of process variables in drilling of carbon fiber reinforced plastics using various multi criteria decision making approaches

Carbon fiber-reinforced polymers are one of the lightweight materials used in structural design due to their exceptional mechanical performances. The drilling operation is indispensable as it facilitates the assembling of various manufactured components. However, drilling of fibrous laminates is deemed difficult in comparison to the traditional metals because of the anisotropic and non-homogeneous nature. The present work addresses the parametric effect on the drilled hole delamination and further reduces it with an optimal combination of parameters for multi-objectives using different multi-criterion decision-making techniques. Initially, the response surface-based regression model of delamination as a function of three static inputs has been developed, further revised with induced thrust as well as mean torque for the improvisation of the prediction capability. Finally, for the overall improvement, a decision-making model has been used that includes grey relation analysis, technique for order performance by similarity to ideal solution, and VIšekriterijumsko Kompromisno Rangiranje method. The delamination was found to be minimum at a low drill point angle (100°), high spindle rotation (2150 min⁻¹ ), and low feed rate (0.025 mm/rev) due to reduced thrust force. The mean absolute prediction error was significantly improved considering root mean square torque rather than axial thrust with process variables.     

Polyaniline as a Gas-Sensor Material

Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized by UV-visible, FTIR, and XRD analyses. The electrical conductivity of the PANI film was studied by a four-point probe method at room temperature. Finally, ammonia gas-sensing characteristics of the prepared polyaniline film were studied by measuring the change in electrical conductivity on exposure to ammonia gas at different concentrations. The influence of concentration of acid during polymerization of aniline and dopant concentration on the gas sensing characteristics of PANI film are reported in this paper.     

e-Commerce security — A life cycle approach

The rapid evolution of computing and communication technologies and their standardizations have made the boom in e-commerce possible. Lowering of the cost of operation, increase in the speed of transactions, and easy global reach to customers and vendors have been the reasons for the overwhelming popularity of this new way of commerce. This article examines the issues related to the security of the assets and transactions in the e-commerce components and activities. Since large public money is involved in the transactions, the role of information security and privacy is not exaggerated in this kind of business. After examining the technologies used in e-commerce, the article goes on to identify the security requirement of e-commerce systems from perceived threats and vulnerabilities. Then e-commerce security is viewed as an engineering management problem and a life cycle approach is put forward. How the e-commerce systems can be made secure using the life cycle approach is outlined. The relevant standards and laws are also discussed in the perspective of e-commerce. The article closes with some future research directions and conclusions.     

Combustion analysis of the diesel–biogas dual fuel direct injection diesel engine – the gas diesel engine

In this investigation, biogas (BG) was used as an alternative fuel in a single-cylinder, four-stroke, air-cooled, direct injection (DI) diesel engine that was operated on a dual fuel mode. Biogas was produced from a non-edible seed de-oiled cake-pongamia pinnata (Karanja), which was collected from the biodiesel industries. The BG was inducted along with the air in suction of the engine at four different flow rates varying from 0.3?kg/h to 1.2?kg/h in steps of 0.3?kg/h. The investigation results revealed that BG inducted at a flow rate of 0.9?kg/h gives better combustion characteristics of engine behaviour than those of other flows throughout the engine operation. The ignition delay (ID) and combustion duration of the engine run by dual fuel operation at a BG flow rate of 0.9?kg/h were found to be longer by about 2 °CA and 2.9 °CA, respectively, in comparison with diesel at full load. The cylinder peak pressure was found to be overall higher by about 11?bar than that of diesel at full load.     

Dietary and bioactive properties of the berries and leaves from the underutilized Hippophae salicifolia D. Don grown in Northeast India

Food Science and Biotechnology - The physico-chemical, polyphenols, antioxidant and antibacterial properties of berries and mixture of male and female leaves of Hippophae salicifolia were...     

Enhancement of thermal properties of polyacrylonitrile by reinforcement of Mg‐Al layered double hydroxide

The in situ polymerization technique was used for synthesis of polyacrylonitrile nanocomposites (PAN/LDH) by reinforcement of different concentrations of Mg‐Al layered double hydroxide (LDH). Molecular interaction between Mg/Al LDH and PAN matrix was studied by Fourier transform infrared spectroscopy. The morphology of PAN/LDH nanocomposite was investigated by field emission scanning electron microscopy. Energy dispersive spectroscopy of nanocomposites were noticed to establish the elemental composition of the composite. High resolution transmission electron microscopy was used to study the nanostructural distribution of LDH with PAN matrix, whereas crystalline patterns were explained by selected area electron diffraction studies. The thermal properties of nanocomposites were studied by thermo‐gravimetric analysis. It was found that, the thermal property of PAN was substantially enhanced due to strong interfacial adhesion of Mg‐Al‐LDH with PAN matrix. Further, it was noticed that the thermal stability of PAN/LDH nanocomposites were increased with increasing concentration of LDH. POLYM. COMPOS., 36:2140–2144, 2015. © 2014 Society of Plastics Engineer     

Indium doped silver oxide thin films prepared by reactive electron beam evaporation technique: electrical properties

The indium doped silver oxide thin films have been prepared at 275 °C on soda lime glass and silicon substrates by reactive electron beam evaporation technique; the deposition rate has been varied (by varying the electron beam current) in the range 0.94–16.88 nm/s keeping the oxygen flow rate constant. These films are polycrystalline. The electrical resistivity for these films decreases with increasing deposition rate. The AIO films prepared with a deposition rate of 5.7 nm/s show near p-type conductivity. The work function has been measured on these films by contact potential method using Kelvin Probe. The surface morphology of the films has been evaluated using atomic force microscopy (AFM). The roles of indium doping and oxygen vacancies in the electrical properties of these films have been analyzed; the ionized impurity scattering is the dominant mechanism controlling the electrical conduction in these films.     

Characterization of dielectric properties of developed CdS‐gum arabic composites in low frequency region

Temperature and frequency dependence of dielectric constant of gum arabic biopolymer—CdS nanocomposites mixed at various proportions have been studied. Powder XRD, transmission electron microscopic (TEM), and differential calorimetric (DSC) studies were made to find out structural and morphological dependence, if any. It is observed that the dielectric constant of GA is enhanced significantly with doping of CdS nanoparticles, and this enhancement shows anomalous dependence on the extent of doping of the nanoparticles and with temperature. POLYM. COMPOS., 108–114, 2016. © 2014 Society of Plastics Engineers     

Recovery of Copper from a Waste Heat Boiler Dust Leach Liquor using LIX 84I and LIX 622N

The dust collected from the waste heat boiler of a copper plant was leached with sulfuric acid and the leach liquor contained 31.63 kg/m³ Cu, 14.78 kg/m³ Fe, 2.21 kg/m³ Zn, 0.26 kg/m³ Co, 0.09 kg/m³ Ni, and 0.23 kg/m³ Cd. The iron content in the leach liquor was precipitated out using Ca(OH)₂ and from the filtrate copper was extracted with the extractants LIX 84I and LIX 622N in kerosene. Extraction of copper with either extractant increased with increasing equilibrium pH and extractant concentration. The McCabe-Thiele plots for quantitative extraction of copper indicated 3-stages at O:A ratio of 3:2 with 30% extractants. The counter-current extraction study showed 0.21 kg/m³ and 6.77 g/m³ copper in the third stage raffinates of LIX 84I and LIX 622N indicating 98.64% and 99.95% extraction, respectively. For extraction of a mole of copper ion, two moles of the extractant was required to release two moles of hydrogen ion to the aqueous phase. The quantitative stripping of copper from the loaded organic phases of LIX 84I and LIX 622N with 180 kg/m³ H₂SO₄ was possible in 3-stages at O:A ratio of 3:1 and 3:2, respectively. The thermodynamic parameters such as ΔH, ΔG, and ΔS were calculated for both the systems. The enthalpy change (ΔH) values were positive for extraction of Cu with either extractant indicating the processes to be endothermic. The IR spectra indicated the association of phenolic-OH group of oxime molecules in the formation of copper complexes.