Investigation of flow and temperature patterns in direct contact condensation using PIV,PLIF and CFD

In this study, experiments have been performed for the steam injected centrally at the bottom of a vertical rectangular water vessel. Instantaneous velocity and temperature field near the plume as well as in the downstream have been measured in a vertical plane through the central axis. For this purpose, Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) have been employed. The velocity profile of the region above the condensation region was found to be self-similar with a small downward velocity near the wall due to recirculation. The instantaneous (20-ns integration time) thermal images obtained from PLIF had a spatial resolution of 100 μm with a field of view of 100×100 mm. The time averaged velocity and temperature profiles are computed from an ensemble of 100 velocity/temperature images. The present work is also concerned with CFD simulation by employing k-ε and large eddy simulation (LES) turbulence models. All the measurements and simulations were carried out by varying nozzle upstream pressure in the range of 0.3–0.35 MPa (corresponding nozzle velocities were in the range of 286–304 m/s) with the nozzle diameter of 1 mm.     

Sea Buckthorn Oil Tocopherol Extraction's By‐Product Utilization in Green Synthesis of Polyurethane Coating

The focus of the present study is to utilize a by‐product obtained during extraction of tocopherols, a valuable vitamin E compound, from sea buckthorn (SBT) oil and in doing so find a reliable alternative to petrochemical based polyols. Bio‐based polyurethane (PU) is prepared by using SBT oil based fatty acid methyl ester polyesteramide polyols (SBTPEP) with toluene diisocyanate (TDI). The fatty acid methyl ester is converted to the corresponding fatty amide by reaction with diethanolamine. The formed fatty amide is then esterified with phthalic anhydride to synthesize polyesteramide polyol. Characterization techniques used to evaluate polyesteramide polyol are Fourier‐transform infrared spectroscopy (FTIR) and NMR. The cured PU coating is also put through various mechanical tests to analyze the physical properties. The cured PU coating shows good surface and mechanical properties. It shows a gloss value of 87.4 and passes impact, adhesion, and chemical resistance tests. It is hydrophobic which is evident from its contact angle of 100.2°. It has good thermal stability which is evident by its glass transition temperature of 53.9 °C. Use of phthalic anhydride contributes to the bio‐based characteristics of synthesized PU. Practical Application: The present study presents a synthesis route which has minimal dependence on hazardous feedstock by utilization of green feedstock. The results obtained from physical and mechanical evaluations favor the use of this PU formulation in the coating sector. The adhesion and impact strength test results show potential application in the industrial sector coatings where the applied coat must be able to withstand high levels of physical stress and strain. The presence of aromatic rings and oil‐based moiety, that is the fatty acid hydrocarbon chain, contributes to the hydrophobic nature of the PU coating. Hydrophobic coatings have tremendous application in various fields such as marine coatings, automotive, electronics, and decorative coatings. These are potential fields of application for the synthesized green PU coating obtained from tocopherol extraction by‐products.     

Energy constraint clustering algorithms for wireless sensor networks

Using partitioning in sensor networks to create clusters for routing, data management, and for controlling communication has been proven as a way to ensure long range deployment and to deal with sensor network shortcomings such as limited energy and short communication ranges. Choosing a cluster head within each cluster is important because cluster heads use additional energy for their responsibilities and that burden needs to be carefully passed around among nodes in a cluster. Many existing protocols either choose cluster heads randomly or use nodes with the highest remaining energy. We present an Energy Constrained minimum Dominating Set based efficient clustering called ECDS to model the problem of optimally choosing cluster heads with energy constraints. Our proposed randomized distributed algorithm for the constrained dominating set runs in O(log n log Δ) rounds with high probability where Δ is the maximum degree of a node in the graph. We provide an approximation ratio for the ECDS algorithm of expected size 8H_Δ∣OPT∣ and with high probability a size of O(∣OPT∣log n) where n is the number of nodes, H is the harmonic function and OPT means the optimal size. We propose multiple extensions to the distributed algorithm for the energy constrained dominating set. We experimentally show that these extensions perform well in terms of energy usage, node lifetime, and clustering time in comparison and, thus, are very suitable for wireless sensor networks.     

Investigations on Factors Affecting Chitosan for Dissolution Enhancement of Oxcarbazepine by Spray Dried Microcrystal Formulation With an Experimental Design Approach

In the present work effect of chitosan on microcrystal formulation for dissolution enhancement of oxcarbazepine using controlled crystallization technique coupled with spray drying was explored. The work was extended for exploration of simplified approach for stable particle size reduction. The study was performed with an experimental design approach i. e. a fractional factorial design of resolution 5 (with all 2 factor interaction) for the screening of predefined independent variables drug concentration, chitosan concentration, feed rate, inlet temperature and percent aspiration for spray drying. Whereas percent drug dissolved, wettability time, flowability in terms of angle of repose and particle size were designated as response variables. Resultant models were analyzed using multiple linear regression analysis, which generated equation to plot response surface curves along with desirability function. Results showed that chitosan concentration had significant effect on dissolution enhancement of oxcarbazepine at a level of 2% w/v. Increase in drug concentration showed decreased dissolution rate however on particle size it did not show statistically significant effect. Topographical characterization was carried out by SEM which showed that feed rate, percent aspiration and inlet temperature had significant effect on particle morphology. For deriving optimized formulation results were analyzed using desirability function for the maximum percent drug dissolved and least drug polymer matrix particle size. DSC studies showed that drug was molecularly associated with chitosan matrix or particles.     

Immobilization of metal nanoparticles on polyurethane membranes: synthesis and electrical properties

Ag and Cu nanoparticles were immobilized into crosslinked polyurethane (PU) membranes by taking advantage of the swelling characteristics of the membranes. The formation, shape and size of the nanoparticles inside the post‐swollen PU membranes were observed by transmission electron microscopy and atomic force microscopy. X‐ray diffraction indicated the presence of the pure Ag and Cu embedded in the amorphous PU matrix. Because of their compatibility, the nanoparticles improved the thermal stability and increased the glass transition temperature of PU. The membranes exhibited interesting conducting behavior with increasing temperature. The metal immobilization increased the ionic conductivity which further increased with temperature, with an activation energy of 0.15 eV indicating a thermally activated conduction mechanism. The optical and electrical properties of these starch‐based membranes can be utilized in the development of novel sensors for biomedical applications. Copyright © 2012 Society of Chemical Industry     

Investigation of flow structures and transport phenomena in bubble columns using particle image velocimetry and miniature pressure sensors

The bubble column reactors are usually operated in a heterogeneous regime where the liquid phase turbulence is generated by the bubble motion and the velocity gradients in the mean motion. The turbulent flow comprises of fluid elements moving in a random fashion with different sizes and energies, called ‘flow structures’. Both the large and small scale flow structures within a reactor play an important role in governing the local momentum, heat and mass transfer. The current work is focused on the estimation of the time averaged flow pattern and flow structures. The experimental data has been collected using miniature pressure sensors, PIV+shadowgraphy and LDA. The data was subjected/analyzed to/with multipoint linear stochastic estimation (MLSE), wavelet transforms, image processing and eddy isolation (EIM) to identify the flow structures. Two bubble columns have been used: a narrow rectangular (2D) column and a cylindrical (3D) column. Wavelet transforms (WT) were applied to isolate individual structures from PIV data to get their shape, size and energy in the 2D column. MLSE has been used to obtain the velocity profiles from pressure fluctuation signals. This data, augmented by PIV and LDA data, is subjected to WT and EIM to get the eddy age and its energy distribution. The data of the eddy shape size and energy was used to predict the mass transfer coefficient in the cylindrical bubble column as a test case. Overall, in this work we present a methodology to utilize the experimental data to get a better insight of the dynamics of flow structures, and propose a path forward for the deeper understanding of transport phenomena in bubble columns.     

Synthesis and anti-bacterial activity of Cu, Ag and Cu-Ag alloy nanoparticles: A green approach

Metallic and bimetallic nanoparticles of copper and silver in various proportions were prepared by microwave assisted chemical reduction in aqueous medium using the biopolymer, starch as a stabilizing agent. Ascorbic acid was used as the reducing agent. The silver and copper nanoparticles exhibited surface plasmon absorption resonance maxima (SPR) at 416 and 584 nm, respectively; while SPR for the Cu-Ag alloys appeared in between depending on the alloy composition. The SPR maxima for bimetallic nanoparticles changes linearly with increasing copper content in the alloy. Transmission electron micrograph (TEM) showed monodispersed particles in the range of 20 ± 5 nm size. Both silver and copper nanoparticles exhibited emission band at 485 and 645 nm, respectively. The starch-stabilized nanoparticles exhibited interesting antibacterial activity with both gram positive and gram negative bacteria at micromolar concentrations.