Water chemistry,solution resistivity,and oxygen reduction reaction in simulated primary coolant of pressurized water reactors

The effect of temperature (25 °C–300 °C) on the ohmic potential drop (ΔE_Ω) and resistivity (R_sol) of a simulated primary coolant of the pressurized water reactors was investigated using electrochemical impedance spectroscopy (EIS) and galvanostatic potentiometry. The variations in the conductivity and pH of the solution showed that by increasing the temperature the magnitude of the R_sol and therefore ΔE_Ω of the system first decreases rapidly (until ~150 °C) and then reaches a relatively stable plateau value. Increasing the pressure of the system decreased the magnitude of the R_sol in the oxygenated coolant. Investigation of the oxygen reduction reaction (ORR) on platinum (Pt), 316L stainless steel (SS), Alloy 690, and carbon steel revealed the great effect of water chemistry, in particular pH on the rate of the ORR on these materials. OH^? adsorption on Pt reduced the rate of the ORR on this metal at temperatures higher than ~100 °C. Finally, it was found that higher H₃O⁺ concentrations reduce the rate of the ORR on iron‐ and nickel‐based alloys, while increasing the OH^? concentration at temperatures higher than ~150 °C accelerates the rate of the ORR on these alloys.     

Applying FCM-ANFIS algorithm as a novel computational method for prediction of viscosity of bitumen and heavy alkane mixture

Recently the studies expressed that the noticeable number of oil reservoirs in all over the world are heavy oil and bitumen reservoirs. So the importance of enhancement of oil recovery (EOR) processes for heavy oil and bitumen reservoirs is highlighted. The Dilution of the reservoir fluid by solvents such as tetradecane is one of well-known methods for these types of reservoirs which effects oil recovery by decreasing viscosity. In the present study, Fuzzy c-means (FCM) algorithm was coupled with Adaptive neuro-fuzzy inference system (ANFIS) to predict viscosity of bitumen and tetradecane in terms of temperature, pressure and weight percent of tetradecane. The coefficients of determination for training and testing steps were calculated such as 0.9914 and 0.9613. The comparison of results and experimental data expressed that FCM-ANFIS algorithm has great potential for estimation of viscosity of bitumen and tetradecane.     

Thin-Layer Drying of Flax Fiber: I. Analysis of Modeling Using Fick's Second Law of Diffusion

Thin-layer drying of moist flax fiber was performed at four temperatures of 30, 50, 70, and 100°C with a constant absolute humidity of 0.0065 kg water per kg dry air. The coefficients of diffusion of the fiber at different drying conditions were estimated by modeling the drying process using the one- to five-term solutions of the second Fick's law of diffusion. The models underestimated the drying process during the initial stages of drying and overestimated this process during the final stages. The estimated coefficient of diffusions ranged from 5.11 × 10^?9 to 1.92 × 10^?8 m²/s and linearly increased with the drying air temperature.     

Thin-Layer Drying of Flax Fiber: III. Influence of Layer Thickness on Drying Parameters

Wet flax fiber was dried after rinsing at four layer thicknesses of 5, 10, 15, and 20 mm using four drying air temperatures of 30, 50, 70, and 100°C. The coefficients of diffusion of flax fiber at different drying conditions were estimated using a three-term series solution of Fick's second law of diffusion. The Page model was used to model the drying characteristic curves. The estimated coefficient of diffusion of the flax fiber and the drying constant of the Page model were both linearly proportional to drying air temperature and increased exponentially with the thickness of the drying layer.     

Polyol-Derived Alkoxide/Hydroxide Base Catalysts II: Transesterification Reactions

Biodiesel, fatty acid methyl ester (FAME), was produced by transesterification of canola oil with methanol in the presence of a series of alkoxide/hydroxide base catalysts produced from glycerol, 1,2-propanediol, 1,3-propanediol, xylitol, or sorbitol produced by dehydration reaction of sodium hydroxide in the presence of polyols. Transesterification reactions proceeded efficiently in the presence of sodium alkoxide catalysts prepared at three different mole ratios of sodium hydroxide to glycerol (1:1, 2:1, and 3:1). The production of methyl ester during the course of the reaction was determined repeatedly and the reaction progress was compared with that achieved in a reaction catalyzed by freshly prepared anhydrous sodium methoxide as a standard catalyst. Sodium alkoxide/hydroxide catalysts activity during the first 2 min of the reaction was in the order of: sorbitol < xylitol < sodium methoxide < 1,2-propanediol < 1,3-propanediol < glycerol regardless of the mole ratio of sodium hydroxide to glycerol. All catalysts showed a higher methyl ester accumulation at higher ratios of sodium hydroxide to polyol and had the following order 1:1 < 2:1 < 3:1 (sodium hydroxide:glycerol). Several of these catalysts were as powerful as sodium methoxide in catalyzing the transesterification reaction at the same mole concentration. All alkoxide/hydroxide catalysts resulted in a high FAME accumulation (>95 wt%) in a single transesterification batch reaction.     

Characterization of triple electrospun layers of PVDF for direct contact membrane distillation process

Recently, electrospinning technique was applied successfully to fabricate porous hydrophobic membranes for MD applications. In this work, a novel triple layer configuration with diameter gradient for PVDF nanofiber membranes is proposed, with the objective of to minimize mass transfer resistance and heat loss. In outer layers of these membranes, the minimum concentration of PVDF (20 wt%) was used to produce bead-free nanofibers with thinner diameters and middle layers were composed of thicker nanofibers formed at higher polymer concentrations (21.5-26 wt%). Characterization of prepared membranes was conducted by the measurement of porosity, thickness, liquid entry pressure (LEP), scanning electron microscopy (SEM), contact angle, thermal and mechanical properties. Direct contact membrane distillation performance of fabricated membranes was tested using 42 g/L NaCl as feed solution. Water permeate flux of triple layer membranes (27.8-31.5 kg/m² h) was found to be considerably higher than that obtained from single layer membrane (15.4 kg/m² h), indicating the proposed configuration can effectively improve evaporation efficiency.     

Solid-phase extraction for simultaneous separation and preconcentration of Fe(III) and Zn(II) traces using three chelatants and Ramelak bark-derived activated carbon as a new bio-sorbent

This article introduces a comparative study for the simultaneous separation and preconcentration of Fe(III) and Zn(II) traces in various water samples using three well-known ligands as chelating agents and activated carbon (AC) derived from Ramelak bark as a new bio-sorbent prior to the determination by ?ame atomic absorption spectrometry. The chelating agents were 4,4’-[(4-Cyano-phenyl)methylene]bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (CMBM), diethyldithiocarbamate (DDTC) and ammonium pyrrolidine dithiocarbamate (APDC). CMBM was synthesized by a procedure reported in the literature. The newly prepared AC was characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared (FTIR) Spectrometry. The analytical parameters affecting the separation efficiency of the analytes including pH, shaking time, chelating agent volume (concentration), sorbent mass, sample ?ow rate and elution conditions were investigated and discussed. Common coexisting ions did not seriously interfere with the separation, showing the good selectivity of the proposed method. The calibration graph was linear in the range of 0.35–70, 0.50–80, 0.9–100, 0.55–75, 0.75–90 and 1.0–120 ng mL^?1 for Fe-CMBM, Fe-DDTC, Fe-APDC, Zn-CMBM, Zn-DDTC and Zn-APDC, respectively. Under optimized conditions, the limits of detection were 0.11, 0.13, 0.27, 0.16, 0.22 and 0.30 ng mL^?1 for Fe-CMBM, Fe-DDTC, Fe-APDC, Zn-CMBM, Zn-DDTC and Zn-APDC, respectively. The proposed method has been applied to the determination of Fe(III) and Zn(II) in different water samples with satisfactory recovery percentages. The developed method, validated with standard reference materials, was used successfully in determining the concentrations of metal ions in water samples.     

Polypyrrole coatings for corrosion protection of Al alloy2024: influence of electrodeposition methods,solvents, and ZnO nanoparticle concentrations

Since ZnO nanoparticles increase the electrical conductivity of the polypyrrole (PPy) coatings, an investigation was carried out to evaluate the effect of ZnO nanoparticles loading on the corrosion protection performance of PPy coatings on AA2024 Al alloy in 3.5% NaCl solution. At first, some measurements were carried out to find the best experimental conditions containing the electrodeposition method, electrosynthesis solvent composition, and ZnO nanoparticles’ concentration for preparing the optimum PPy coating on Al alloy2024. Three different methods of electrodeposition, namely: cyclic voltammetry, galvanostatic, and potentiostatic techniques were analyzed. The anti-corrosion performance of the PPy coatings was evaluated by electrochemical impedance spectroscopy and Tafel polarization methods. The PPy prepared by potentiostatic method exhibited the best performance against corrosion of Al alloy2024 in 3.5% NaCl solution. Then, different mixtures of H₂O/ethanol were tested as electrosynthesis solvents for preparation of PPy coatings on the alloy by optimized electrodeposition mode (i.e., potentiostatic). In evaluation of the prepared coatings, the pure water was introduced as the optimum solvent in electrodeposition of PPy. The investigation of different ZnO nanoparticles’ concentrations proved that the PPy coating containing 0.025% ZnO nanoparticles was the optimum coating against the corrosion of Al alloy in NaCl solution. Finally, the long-term evaluation of the corrosion protection performance of the coatings revealed that the optimum coating provided suitable protection against corrosion up to 14 days after immersion.

     

Friction and compression characteristics of chickpea flour and components

Chemical composition and selected physical properties of chickpea flour, the starch fraction and the protein fraction were determined. Coefficient of internal friction, coefficient of external friction (on steel, concrete, Teflon and polypropylene), cohesion and adhesion of samples were measured. Chickpea flour and starch fraction had the highest coefficient of internal friction and cohesion, respectively. The coefficient of external friction of chickpea flour and components on concrete was markedly higher than other surfaces. The starch fraction had the highest compressibility and asymptotic modulus at most of the preset loads. The compressibility and asymptotic modulus increased with porosity. Chickpea flour with the lowest porosity had the lowest asymptotic modulus. All samples underwent particle rearrangement during compression.     

Application of Compressible Volume of Fluid Model in Simulating the Impact and Solidification of Hollow Spherical ZrO<Subscript>2</Subscript> Droplet on a Surface

Applications of hollow spherical particles in thermal spraying process have been developed in recent years, accompanied by attempts in the form of experimental and numerical studies to better understand the process of impact of a hollow droplet on a surface. During such process, volume and density of the trapped gas inside droplet change. The numerical models should be able to simulate such changes and their consequent effects. The aim of this study is to numerically simulate the impact of a hollow ZrO₂ droplet on a flat surface using the volume of fluid technique for compressible flows. An open-source, finite-volume-based CFD code was used to perform the simulations, where appropriate subprograms were added to handle the studied cases. Simulation results were compared with the available experimental data. Results showed that at high impact velocities (U ₀ > 100 m/s), the compression of trapped gas inside droplet played a significant role in the impact dynamics. In such velocities, the droplet splashed explosively. Compressibility effects result in a more porous splat, compared to the corresponding incompressible model. Moreover, the compressible model predicted a higher spread factor than the incompressible model, due to planetary structure of the splat.