Computational fluid dynamics modeling of immobilized photocatalytic reactors for water treatment

A computational fluid dynamics (CFD) model for the simulation of immobilized photocatalytic reactors used for water treatment was developed and evaluated experimentally. The model integrated hydrodynamics, species mass transport, chemical reaction kinetics, and irradiance distribution within the reactor. The experimental evaluation was performed using various configurations of annular reactors and ultraviolet lamp sizes over a wide range of hydrodynamic conditions (350 < Re < 11,000). The evaluation showed that the developed CFD model was able to successfully predict the photocatalytic degradation rate of a model pollutant in the analyzed reactors. In terms of hydrodynamic models, the results demonstrated that the laminar model performs well for systems under laminar flow conditions, whereas the Abe‐Kondoh‐Nagano low Reynolds number and the Reynolds stress turbulence models give accurate predictions for photoreactors under transitional or turbulent flow regimes. The performed analysis confirmed that degradation rates of organic contaminants in immobilized photocatalytic reactors are strongly limited by external mass transfer; as a consequence, the degradation prediction capability of the CFD model is largely determined by the external mass transfer prediction performance of the hydrodynamic models used. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Modification of regenerated cellulose membrane by impregnation of silver nanocrystal clusters

Regenerated cellulose forms a very important class of basic material with diverse applications because of its hydrophilicity and insolubility in water. Thus, one of the applications of regenerated cellulose is used to fabricate membranes. However, short operational lifetime is one of the disadvantages of the regenerated cellulose. In this research, surface modification of the cellophane membrane was carried out by silver nanoclusters. Silver colloids were formed in situ by chemical and photochemical reduction, and then, silver particles were deposited uniformly onto the surface of the cellophane membrane. The maximum amount of silver deposition was found to be 2.55% by weight in this modification. The modified and unmodified membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis to indicate silver nanocrystalline cluster particles on the modified membrane. SEM images indicate well-dispersed silver particles with an average size of 0.65 μm on the membrane. XRD patterns showed that the size of the silver crystals was 3.9 nm. The surface properties of modified and unmodified membranes were studied by the contact angle. Water absorption, oxidative resistance, salt permeability, and thermal stability were investigated. This study revealed that the modified membrane is more resistant against the oxidative cleavage than the unmodified one moreover, the salt permeability increased after the treatment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48292.     

DETERMINATION OF SOLID SURFACE TENSION FROM CONTACT ANGLES: THE ROLE OF SHAPE AND SIZE OF LIQUID MOLECULES

Accurate surface tension of Teflon® AF 1600 was determined using contact angles of liquids with bulky molecules. For one group of liquids, the contact angle data fall quite perfectly on a smooth curve corresponding to γ_sv = 13.61 mJ/m², with a mean deviation of only ±0.24 degrees from this curve. Results suggest that these liquids do not interact with the solid in a specific fashion. However, contact angles of a second group of liquids with fairly bulky molecules containing oxygen atoms, nitrogen atoms, or both deviate somewhat from this curve, up to approximately 3 degrees. Specific interactions between solid and liquid molecules and reorientation of liquid molecules in the close vicinity of the solid surface are the most likely causes of the deviations. It is speculated that such processes induce a change in the solid-liquid interfacial tension, causing the contact angle deviations mentioned above. Criteria are established for determination of accurate solid surface tensions.     

Current status of droplet evaporation in turbulent flows

This article reviews the available literature results concerning the effects of turbulence on the transport (heat and mass transfer) rates from a droplet. The survey emphasizes recent findings related specifically to physical models and correlations for predicting turbulence effects on the vaporization rate of a droplet. In addition, several research challenges on the vaporization of fuel droplets in turbulent flow environments are outlined.     

Modelling of acrylic cut-pile carpet compression properties by means of expert systems based on carpet structural parameters

Abstract

Compression properties of carpet are a detrimental factor influencing carpet wear performance. In fact, carpet compression behavior determines carpet serviceability which in turn affects carpet appearance. Therefore, it is important to predict the carpet compression behavior in order to reduce the product cost. In this paper, a fuzzy logic model for prediction of compressional properties of acrylic cut-pile carpets is implemented in terms of the carpet structural parameters including carpet pile density, linear density of pile yarns and carpet pile height. In order to provide experimental data, six different acrylic cut-pile carpet samples fabricated by using six different acrylic spun pile yarns with yarn count of 18/3, 21/3, 27/3, 30/3, 33/3 and 36/3?Nm. Half of each provided carpet subjected to re-shearing process. All 12 carpet samples in two different cases (normal and reduced pile height) have been tested by standard carpet static and dynamic loading tests to measure thickness-loss as one of compression properties. Fuzzy logic model has been implemented and improved using genetic algorithm. Results show that correlation coefficients of model predictions with experimental values are 0.97, 0.98, 0.98 and 0.98 for carpet thickness-loss after low dynamic, high dynamic and static loading with short and long relaxation times, respectively. Also, linear regression trend between predicted and experimental values represented with a slope near to 1 and almost small bias (intercept). The result indicates that the developed fuzzy logic model is a reliable model predicting the acrylic cut-pile compression behavior.     

Monitoring of laser processing using induced current under applied electric field on laser produced-plasma

A new electrode circuit for measuring the induced current from laser plasma produced during laser material processing has been devised. The new electrode circuit has greatly increased the possible separation between the electrodes and the workable probing distance of the electrodes from the processed sample surface, namely 38 and 22 mm, respectively, sufficing the requirements of actual industrial laser material processing, avoiding direct contact of the electrodes with the big plasmas and profound sputtering. Several possible electrode configurations were investigated to accommodate the specific needs of the actual laser processing. It was shown that this technique is a very effective tool for accurately determining the moment of completion of penetration, as required in the laser piercing process. In contrast to this, the optical method currently in use cannot accurately determine the piercing completion moment due mainly to the disturbance from smoke arising at the processing point. A preliminary work using a CW CO₂ laser normally used in the actual industrial material processing was also made, resulting in a strong induced current signal corresponding to the laser pulse duration and frequency. The signal was successfully used for monitoring the penetration completion in a stainless steel plate drilling process. This reveals that this technique can be used for monitoring actual industrial material processing using high power lasers.     

An ideal-seeking fuzzy data envelopment analysis framework

Data envelopment analysis (DEA) is a widely used mathematical programming approach for evaluating the relative efficiency of decision making units (DMUs) in organizations. Crisp input and output data are fundamentally indispensable in traditional DEA evaluation process. However, the input and output data in real-world problems are often imprecise or ambiguous. In this study, we present a four-phase fuzzy DEA framework based on the theory of displaced ideal. Two hypothetical DMUs called the ideal and nadir DMUs are constructed and used as reference points to evaluate a set of information technology (IT) investment strategies based on their Euclidean distance from these reference points. The best relative efficiency of the fuzzy ideal DMU and the worst relative efficiency of the fuzzy nadir DMU are determined and combined to rank the DMUs. A numerical example is presented to demonstrate the applicability of the proposed framework and exhibit the efficacy of the procedures and algorithms.     

Detecting critical regions in multidimensional data sets

We propose a new approach, based on the Conley index theory, for the detection and classification of critical regions in multidimensional data sets. The use of homology groups makes this method consistent and successful in all dimensions and allows us to generalize visual classification techniques based solely on the notion of connectedness which may fail in higher dimensions.