Three-dimensional Numerical Study of Laminar Confined Slot Jet Impingement Cooling using Slurry of Nano—encapsulated Phase Change Material

This Article presents a three dimensional numerical model investigating thermal performance and hydrodynamics features of the confined slot jet impingement using slurry of Nano Encapsulated Phase Change Material (NEPCM) as a coolant. The slurry is composed of water as a base fluid and n-octadecane NEPCM particles with mean diameter of 100nm suspended in it. A single phase fluid approach is employed to model the NEPCM slurry.The thermo physical properties of the NEPCM slurry are computed using modern approaches being proposed recently and governing equations are solved with a commercial Finite Volume based code. The effects of jet Reynolds number varying from 100 to 600 and particle volume fraction ranging from 0% to 28% are considered. The computed results are validated by comparing Nusselt number values at stagnation point with the previously published results with water as working fluid. It was found that adding NEPCM to the base fluid results with considerable amount of heat transfer enhancement.The highest values of heat transfer coefficients are observed at H/W=4 and C_m=0.28. However, due to the higher viscosity of slurry compared with the base fluid, the slurry can produce drastic increase in pressure drop of the system that increases with NEPCM particle loading and jet Reynolds number.     

Flow‐based electromagnetic‐type energy harvester using microplanar coil for IoT sensors application

Battery is the sole power source for Internet of thing (IoT) sensors. Due to limited shelf life, the batteries are required to be replaced intermittently. This periodic replacement of batteries is inflated in terms of both logistics and time. This article illustrates conceptual design, development, and characterization of a flow‐based electromagnetic‐type energy harvester (F‐EH) using microplanar coil for IoT sensors application. The F‐EH converts hydro energy into useful electrical energy utilizing electromagnetic transduction mechanism. The microfabrication and macrofabrication techniques adopted to manufacture harvester's components are presented. The F‐EH has been successfully characterized by laboratory scale experimental flow test loop commissioned for this work. Experimentation with associated uncertainty analysis prevails that at a matching impedance, the F‐EH can generate a 686 μW of maximum power at an operating flow rate of 12 L/min with an uncertainty of 8.1%.     

Tailoring structural,morphological and mechanical characteristics of mono-crystalline diamond-reinforced polyacrylonitrile based electrospun fibers

Composites of diamond-reinforced particles offer extraordinary thermal- and mechanical characteristics attributable to their manageable outer surface and huge available uppermost layer. Uniform distribution of diamond powder in polymeric matrix, and enhanced interactions between them are the two significant problems to attain robust polymer composites. In this work, the crystalline diamond particles as received and chemically modified ones were integrated in polyacrylonitrile (PAN) matrix uniformly by electrospinning method. This procedure avoided agglomeration of the reinforced diamonds through uniform distribution in the polymer matrix. The shapes of diamond-integrated PAN fibers were attuned by adapting diamond loading, polymer concentration, flow rate, and applied voltage to achieve beads free fibrous structures. PAN was chosen as a carrier polymeric-matrix to enhance the electrostatic forces between functionalized diamond-particles and PAN molecular chains. Tensile tests showed that the loading of 2 wt% modified diamond-particles improved Young’s modulus of fibers by 74.94% and tensile strength by 125%. Therefore, modification of the outer surface of the diamond particles improved the chemical interactions between the diamond surface and matrix, and stress was transferred to the diamond particles in composite fibers. Additionally, thermal stabilities of the diamond-based polymer composites were enhanced by the integration of diamond powder in composite fibers.

     

Sulfonation of low‐density polyethylene and its impact on polymer properties

Sulfonation of polymers is of great importance for the packaging industry mainly due to its effect on the alteration of surface functionality of polymer films. In this study we customized liquid phase sulfonation of low‐density polyethylene (LDPE) swelling the polymer by using a combination of polar and nonpolar solvents. Swollen polymer was treated with sulfuric acid of varying concentrations with continuous mixing for in‐depth sulfonation of the polymer. Presence of cyclohexane and ethanol, as polar and nonpolar reagents, not only kept the batch under isothermal conditions but also homogenously influenced in‐depth functionalization of LDPE. The durability of the sulfonated polymer was determined by grinding the test samples 30 days after the reaction. Fourier transform‐infrared spectroscopy indicated presence of functional group moieties, which is also supported by increase of 5% and 1.35% in density and sulfur contents of the polymer, respectively. Contact angle measurements indicate 30° decrease in values of the sulfonated polymer which corresponds with decrease in carbon to hydrogen ratio (from 5.9 to 5.3) and increase in sulfur to carbon ratio (up to 0.0184) resulting from the sulfonation of the polymer. Differential scanning calorimetery results indicate almost linear reduction in the crystallinity of LDPE with an increase in acid concentration used for the sulfonation reaction. POLYM. ENG. SCI., 54:2522–2530, 2014. © 2013 Society of Plastics Engineers     

Tolerance-based localization algorithm: form tolerance verification application

Current localization techniques have been successfully used for aligning sculptured surfaces with CAD models in inspection applications. However, tolerance specifications are not considered as an integral part of the localization process. The tolerance verification and comparison with measured surfaces occur at a later step to accept or reject the manufactured part. This two-step process prolongs the inspection time. For the first time, this paper presents a novel localization algorithm for inspection that integrates the tolerance specifications as an optimality criterion. A closed-form solution algorithm that applies 3D rigid body transformation using quaternion and uses a minimum acceptable deviation zone approach was developed. The formulation is based on the mathematical definitions from ANSI Y14.5.1 standards (American National Standard Institute) for form tolerances. The new iterative minimum acceptable deviation zone localization algorithm is formulated using four types of form tolerances: straightness of a median line, straightness of a surface line, flatness and cylindricity. It is applied and compared to several benchmark examples for validation. The results demonstrated the ability of the new localization approach to achieve comparable results but with less computation effort due to using a constraint satisfaction problem and a closed-form solution algorithm in the formulation. The merit of the new approach stems from its ability to increase the efficiency of tolerance verification during the inspection process. The applicability of the proposed algorithm to various types of tolerance is highlighted.     

Synthesis of physically cross-linked gum Arabic-based polymer hydrogels with enhanced mechanical,load bearing and shape memory behavior

The TiO2 dispersed physically cross-linked polymer hydrogels were synthesized through a single step free radical addition polymerization mechanism based on acrylic acid and gum Arabic (GA) as polymer constituents, and ferric ions (Fe3+) as physical cross-linker. The effect of TiO2 powder was investigated on thermal and mechanical properties of the hydrogels by dispersion of 0.01, 0.02 and 0.03 g of TiO2 in hydrogels. The prepared hydrogels were successfully characterized through FTIR, XRD, SEM and thermogravimetric analysis (TGA). For the mechanical properties, dynamic mechanical analysis and universal testing machine (UTM) were used. The DMA results showed that the storage modulus was increased with the TiO2, while UTM results showed that 0.02 g of TiO2 powder significantly enhanced the fracture stress, elastic modulus, toughness and stretchability by 4514%, 4328%, 4124% and 20%, respectively, compared to the virgin hydrogels. Cole–Cole plot confirmed the homogeneity and viscoelastic behavior of the system, while manual load bearing and shape memory test showed that the hydrogels bear a load of 2.5 kg for a long time and it is recovered within 10 s to its original state. The materials can be applied for the synthesis of artificial body parts in the field of bio-engineering. The use of un-modified GA for the synthesis of hydrogels will open a new window for the researchers working in this field.     

Reinforcing Effects of Modified Nanodiamonds on the Physical Properties of Polymer-Based Nanocomposites: A Review

Exceptional mechanical and other physical properties of nanodiamond (ND) have recently attracted much attention. For thermosetting polymers, the reinforcing effects of as-received and amine-functionalized nanodiamonds on the mechanical and tribological properties have been examined and demonstrated the advantages of covalent incorporation of ND into epoxy structure resulting in strong nanofiller-matrix interface. In epoxy matrix composites, the ultimate mechanical reinforcement was achieved using high loadings level of ND powder along with improved thermal conductivity and reduced friction coefficients. In this regard, several complementary mechanical characterization techniques including pin-on-disk, nanoindentation, vickers, tensile, and compression were used to study the reinforcing mechanisms.     

Molecular rectification: Confirmation of its molecular origin by chemical suppression of the electrical asymmetry

Bis[N-(ω-decyl)-5-(4-dimethylaminonaphthalen-1-yl-methylene)]-5,6,7,8-tetrahydroisoquin-olinium]-disulfide diiodide forms self-assembled monolayers (SAMs) on gold substrates in which the acceptor–(π-bridge)–donor moieties are aligned: Au|Au–S–C₁₀H₂₀–A⁺–π–D (I^?). These diode-like molecules exhibit rectification ratios of 30–80 at ±1 V but display symmetrical current–voltage (I–V) characteristics when exposed to HCl and rectify again when exposed to NH₃. This reversible switching is explained by protonation/deprotonation of the amino group which disrupts/restores the donor–acceptor combination and provides evidence of the molecular origin of the electrical asymmetry.