Effects Of Operating Parameters Research Articles

Construction of Ag/Ag2S/CdS Heterostructures through a Facile Two-Step Wet Chemical Process for Efficient Photocatalytic Hydrogen Production

We have demonstrated a two-step wet chemical approach for synthesizing ternary Ag/Ag2S/CdS heterostructures for efficient photocatalytic hydrogen evolution. The CdS precursor concentrations and reaction temperatures are crucial in determining the efficiency of photocatalytic water splitting under visible light excitation. In addition, the effect of operational parameters (such as the pH value, sacrificial reagents, reusability, water bases, and light sources) on the photocatalytic hydrogen production of Ag/Ag2S/CdS heterostructures was investigated. As a result, Ag/Ag2S/CdS heterostructures exhibited a 3.1-fold enhancement in photocatalytic activities compared to bare CdS nanoparticles. Furthermore, the combination of Ag, Ag2S, and CdS can significantly enhance light absorption and facilitate the separation and transport of photogenerated carriers through the surface plasma resonance (SPR) effect. Furthermore, the Ag/Ag2S/CdS heterostructures in seawater exhibited a pH value approximately 2.09 times higher than in de-ionized water without an adjusted pH value under visible light excitation. The ternary Ag/Ag2S/CdS heterostructures provide new potential for designing efficient and stable photocatalysts for photocatalytic hydrogen evolution.

Self-rotation induced regeneration of filter media to enhance the oil-water separation in a microchannel filter

The regeneration of filter media was crucial to the filtration performance of the oily wastewater. Herein, a novel hydrocyclone-induce approach was proposed for filter media regeneration, followed by an exploration of oil desorption feasibility and mechanism. The effect of structural and operation parameters of a hydrocyclone on the particle self-rotation was extensively analyzed by numerical simulation, and its feasibility for oil desorption from the filter media was subsequently investigated. A hydrocyclone-intensified filtration method that combined by the unit of filtration and hydrocyclone self-rotation regeneration was proposed, and the effect of hydrocyclone-induced filter media regeneration on the subsequent oily wastewater filtration was also explored. The ideal specifications of the hydrocyclone were concluded to be an overflow pipe insertion of 120 mm, and a cone angle of 60° for the optimal self-rotation velocity. The hydrocyclone-induced regeneration presents a remarkable oil desorption efficiency, and the oil concentration of filter media reduced from 9.43 % to 6.94 %, 4.33 %, and 3.43 % as the flowrate increased from 1.8 × 105 L·m−2·h−1 to 5.4 × 105 L·m−2·h−1. The adhered oil was exfoliated due to the centrifugal force caused by the revolution and self-rotation of the media particles, while the filter media spun in a hydrocyclone. The average effluent oil concentration in the raw oily wastewater was reduced to 12.2 mg/L during the pilot-scale test, indicating that the hydrocyclone regeneration benefits the continuous oil-water separation. It is believed that this work might provide a unique and efficient method for oily wastewater treatment with the integration of filtration and hydrocyclone regeneration.

Anion exchange membrane water electrolysis: Numerical modeling and electrochemical performance analysis

In this paper, a three-dimensional numerical model is developed for an anion exchange membrane electrolyser cell (AEMEC) with a double serpentine flow field pattern. The focus on the AEMEC is due to its benefits, including the solid membrane, inexpensive catalysts and membrane, and high stability. The effect of important operating parameters, i.e. cell temperature and cathode pressure, on the performance of the electrolyser is numerically modeled by considering different causes of performance degradation. The polarization curve, uniformity index, and the distribution of the hydrogen concentration, current density, temperature, and pressure in different operating conditions are presented. By increasing the operating temperature and decreasing the cathode pressure, the voltage of the elctrolyser decreases. Due to the higher concentration of water at the inlet of the cathode channel, more hydrogen is produced, and the current density is higher. The maximum current density and hydrogen concentrations are 7868Am2 and 0.898molm3, respectively, when the operating condition is set to the temperature of 343 K, the pressure of 1 bar, and the cell voltage of 1.85 V.

Thermal-hydraulic-mechanical-chemical modeling and simulation of an enhanced geothermal system based on the framework of extended finite element methods - Embedded discrete fracture model

The thermo-hydro-mechanical-chemical (THMC) coupling process plays a crucial role in Enhanced Geothermal System (EGS), particularly during long-term heat extraction. However, most models for fractured reservoirs are computationally expensive, with very dense grids required, especially near fractures, limiting their practical use in EGS research. The embedded discrete fracture model (EDFM) can construct fracture and matrix grids independently, significantly reducing computational complexity while maintaining high accuracy. Although it is suitable for efficiently evaluating the long-term performance of heat extraction in fractured reservoirs, there are few THMC-coupled models based on EDFM, and THMC coupling effects have often been overlooked in evaluations of the environmental benefits of EGS. To address this, a fully THMC-coupled model based on EDFM and the extended finite element method (XFEM) is proposed and verified. The evolution of heat production and environmental benefits of an EGS over 30 years are presented. The results show that the production temperature and electric power remain highly efficient in the first 5 years and decrease by 7.8% and 15.4% respectively over 15 years. Moreover, the total amount of extracted heat during this period is 6.52 × 1012 kJ, which is equivalent to saving 22.26 × 108 kg of coal consumption and reducing CO2 emissions by 5.83 Mt, SO2 emissions by 189.22 × 105 kg, and NOx emissions by 166.96 × 105 kg. These findings highlight the significant potential of geothermal energy for energy supply and environmental benefits. Additionally, the study investigates the effects of critical operating and physical parameters on the production performance of EGS, including injection temperature, injection flow rate, initial reservoir temperature, and initial reservoir permeability. This work serves as a reference for both the theoretical THMC coupled model and practical EGS engineering.

Lipid extraction and CO2 capture with switchable polarity solvent

In this study, lipid extraction and CO2 capture are combined using N, N-dimethylcyclohexylamine (DMCHA) as switchable polarity solvent. The effects of operation parameters are discussed according to the CO2 absorption/desorption and lipid/DMCHA recovery results. A triphasic models considering lipid, water, and gas phases are established to analyze the kinetic behaviors. The results show that DMCHA is reversible through CO2 absorption/desorption, and the enhanced dispersion of droplets and bubbles in water phase improves the lipid/DMCHA recovery and CO2 absorption/desorption. The triphasic kinetic models fit well with experimental data, and gas–liquid mass transfer is regarded as the rate-determining step. The lower interfacial areas result in the poorer gas–liquid mass transfer for the DMCHA recovery than lipid recovery process.

Evaluation of atrazine degradation by iron persulfate activation process in aqueous phase using Taguchi approach

Atrazine (ATZ) is one of the most widely used herbicides for the control of annual broadleaf and grassy weeds in the world. Its residual in the environment is of great concern. This research work primarily focused on examining ATZ degradation by the ferrous ion activated persulfate (PS) oxidation process (Fe2+-AP process) and the influence of oxidative parameters on the degradation of ATZ in aqueous phase. The Taguchi Design of Experiment methodology was used to explore the effects of various operational parameters, including ATZ concentration, dosage of Fe2+, dosage of PS, and pH condition (Taguchi L9 orthogonal array). The optimal operational conditions were then determined based on the results of ANOVA statistical analysis. Operational conditions included ATZ at an initial concentration of 5 mg/L, with initial concentrations of 1 mM Fe2+, 10 mM PS, and pH = 3, at 20oC, for a reaction time period of 3 h. The sensitivity of factors for the ATZ degradation followed the decreasing order: PS concentration, pH, ATZ concentration and Fe2+ dosage. The results of this study provide useful operational conditions for the Fe2+-AP process, for application to field remediation of ATZ contamination.

A simulation study on the condensation flow and thermal control characteristics of mixed refrigerant in a dimpled tube

In this study, the condensation flow and heat transfer characteristics of ethane/propane in the dimple tube have been numerically investigated, and the liquid droplet entrainment caused by the dimple structure was considered. The effects of operation and structure parameters on flow and heat transfer were analyzed, including different dimple depths, helical pitch, and dimple pitch. The results showed that the dimple tube had a higher heat transfer coefficient compared to the smooth tube, which increased with the increase in the mass flow rate and the decrease in the saturation temperature. The effect of dimple depth on heat transfer is greater than that of the dimple pitch or helical pitch, and the dimple depth will cause the local mass transfer rate to increase under high vapor quality. Meanwhile, the existing heat transfer correlations for smooth tubes were compared, and a condensation heat transfer correlation suitable for the mixed refrigerant in the dimple tubes was proposed with an average deviation of 6.3%.The conclusions obtained can provide support for the optimization design of liquefied natural gas plants.

Effects of cold-rolling operation parameters on the surface quality of stainless steel and titanium strips with oil pits

Effects of cold-rolling operation parameters on the surface quality of stainless steel and titanium strips with oil pits

Use of Pitzer’s model to calculate thermodynamic properties of aqueous electrolyte solutions of sulfuric acid

Over this study we calculated the coefficients of activity of different species and the concentration in the presence of H+ ion when H2SO4 is alone in solution. The coefficient of average activity was calculated using the model of Pitzer. The constants of dissociation of these reactions were calculated from the values of the free standard energies. The reaction reaches a balance while producing H+, HSO4- and SO42-. The research reported here concentrated on the effect of some important operational parameters on dissolution process. The parameters were investigated and their ranges are as follows: initial molality ranging from 0.001 to 5 mol.kg-1 and temperatures between 25 and 200°C. Fortran 90 (Mathematical formula translating system) was used to perform all mathematical calculations. The numerical code can be used to calculate the molarity of ion H+ of an aqueous solution of sulfuric acid. The objective of the present work is to optimize the parameters of leaching such as activity of sulfuric acid on the dissociation phenomena.

Molybdenum Carbide/Ni Nanoparticles Embedded into Carbon Nanofibers as an Effective Non-Precious Catalyst for Green Hydrogen Production from Methanol Electrooxidation.

Molybdenum carbide co-catalyst and carbon nanofiber matrix are suggested to improve the nickel activity toward methanol electrooxidation process. The proposed electrocatalyst has been synthesized by calcination electrospun nanofiber mats composed of molybdenum chloride, nickel acetate, and poly (vinyl alcohol) under vacuum at elevated temperatures. The fabricated catalyst has been characterized using XRD, SEM, and TEM analysis. The electrochemical measurements demonstrated that the fabricated composite acquired specific activity for methanol electrooxidation when molybdenum content and calcination temperature were tuned. In terms of the current density, the highest performance is attributed to the nanofibers obtained from electrospun solution having 5% molybdenum precursor compared to nickel acetate as a current density of 107 mA/cm2 was generated. The process operating parameters have been optimized and expressed mathematically using the Taguchi robust design method. Experimental design has been employed in investigating the key operating parameters of methanol electrooxidation reaction to obtain the highest oxidation current density peak. The main effective operating parameters of the methanol oxidation reaction are Mo content in the electrocatalyst, methanol concentration, and reaction temperature. Employing Taguchi's robust design helped to capture the optimum conditions yielding the maximum current density. The calculations revealed that the optimum parameters are as follows: Mo content, 5 wt.%; methanol concentration, 2.65 M; and reaction temperature, 50 °C. A mathematical model has been statistically derived to describe the experimental data adequately with an R2 value of 0. 979. The optimization process indicated that the maximum current density can be identified statistically at 5% Mo, 2.0 M methanol concentration, and 45 °C operating temperature.

Investigating the Planarization of Al0.5CoCrFeNi2 High-Entropy Thin Films Through Chemical Mechanical Polishing

High-entropy alloys (HEAs) exhibit a variety of characteristics and provide industries with more options in high-end applications, as HEAs differ from the design concept of conventional alloys. In semiconductor manufacturing processes, HEAs are potential candidates for diffusion barrier layers due to their sluggish diffusion behavior. As a functional interlayer inside three-dimensional integrated circuits (3D-ICs), this material should be prepared as a thin-film with wafer-level flatness. Chemical mechanical polishing (CMP) is a common process used to planarize ICs; however, very little literature has reported its development in complex alloys, and CMP has not been applied to HEAs. In this study, Al0.5CoCrFeNi2 HEA was prepared as thin films of different crystallinities to investigate the effects of CMP operation parameters in planarizing these complex concentrated alloys. The HNO3-based slurry mainly causes the oxidation of Ni, Cr, and Fe in HEA films and then causes the film surface to soften, creating a surface more conducive to mechanical grinding. Both chemical and mechanical forces can enhance the material removal rate (MRR) in the CMP process; more importantly, a moderate rotation speed of 40 rpm and a low down force of 50 g/cm2 are necessary to achieve nanoscale flatness. Additionally, a useful prediction relationship, the Preston equation, for the CMP process applied to HEA systems was established.

Intensification of esterification reaction microbubble mediated reactive distillation

The current study is based on the microbubble mediated reactive distillation by converting conventional homogeneous liquid-liquid system into a heterogeneous vapour-liquid system. Microbubbles owing to their higher surface area to volume ratio provides better mass transfer as well increasing the conversion and rate of reaction. To prove the hypothesis, production of methyl acetate was investigated because of its industrial importance. The experimental plan was designed using Response Surface Methodology (RSM). It allowed analysing the effects of operational parameters simultaneously. The kinetics investigation demonstrated that the esterification reaction occurs, indeed, on the vapour liquid interface at the skin/surface of the bubble and follows pseudo-first order kinetics. The maximum conversion of the process was found to be 91% in 20 min which is significantly higher than any previous study. Furthermore, RSM and Gated Recurrent Unit (GRU) were employed to develop models to analyse the correlations among parameters and to predict the responses. The GRU produced higher R2 = 0.9981 as compared to R2 = 0.9715 produced by RSM. The results depict that GRU model is more robust and reliable than Response Surface Methodology for parameter interaction study and response prediction.

Removal of Colour and COD from vegetable tannery wastewater onto bone char– Effect of process parameters, adsorption mechanism, kinetics and equilibrium modelling

ABSTRACT In this study, bone char derived from head bones of cattle was used as an adsorbent in the removal of Chemical Oxygen Demand (COD) and colour from vegetable tannery wastewater. The char was characterized by proximate analysis, pHpzc, FTIR, BET surface area analysis and SEM-EDX spectroscopy. The effects of operational parameters (pH, contact time, adsorbent mass and temperature), the kinetics and isotherms of the adsorption process were investigated. Optimal conditions for maximum adsorption of COD (77.4%) and colour (98.01%) occurred at pH 2 after 60-minute contact time with 50 g of adsorbent at 25°C. The adsorption kinetics were analyzed using Elovich and the pseudo-first and – second-order models. The pseudo-second order model gave the best fit for the kinetic data. Application of the intra-particle diffusion and Boyd models to the kinetic data revealed that COD and colour adsorption onto the bone char were predominantly controlled by film diffusion. The Langmuir, Freundlich, Temkin and Redlich-Peterson isotherm models were applied. The Freundlich model best described the adsorption of COD and colour. The maximum monolayer adsorption capacities for COD and colour were 559.61 mg/g and 2011.76 Pt-Co/g, respectively. These results indicate that bone char can be an effective low-cost adsorbent in wastewater treatment.

Configurations and Operation Methods of Diesel-Based Solid Oxide Fuel Cell System

Solid oxide fuel cell (SOFC) can use a wide variety of carbon-based fuels. Diesel can act as a high-quantity fuel because of its high heat value and ease of transport. In this study, three different system configurations were proposed by a model in ASPEN PLUS V12 and fitted by data measured in the large size cell. The effects of key operation parameters, including reforming temperature, steam-to-carbon ratio (S/C) and recycling rate of the anode off-gas, were studied, which were characterized by the system efficiency and output power. As a result, the highest system efficiency was gotten with a water condenser and an anode off-gas recycling module in the system. The best operation method occurs when the thermal load of the diesel reformer is compensated by the heat released by anode off-gas combustion. This research will lay a theoretical foundation for the upcoming design of a physical diesel-based SOFC system.

Study of the Adsorption Efficacy of Cr(III) on a Metal Oxide-Based Material Derived from the Quartz Sand Enrichment Process

In the present study, the efficacy of chromium removal from water media was studied. For this purpose, a metal oxide based material, derived from the enrichment process of quartz coastal sand was used as possible adsorbent of chromium (III) ions. Following additional modification of the adsorbent, the effect of operational parameters including pH, contact time and Cr(III) concentration were studied according to one-factor-at-a-time procedure. Adsorption efficacy was assessed by the measurement of the remaining chromium concentration in solution, after adsorption. Atomic absorption spectroscopy technique, with flame atomization was used for the determination of chromium concentration in solution. Obtained results revealed that selected material exhibited higher adsorption efficacy in alkaline solution (pH = 6-9). The maximum removal efficacy (>93%) was achieved after 180 minutes of contact time, with an adsorbent dosage of 5 g/L and initial chromium concentration 20 mg/L. The adsorption process for Cr(III) follow the Freundlich isotherm and gives high correlation coefficient R². Calculations performed based on the Langmuir isotherm showed that the maximum adsorption efficiency of Cr³⁺ in the natural metal-oxide material has resulted 10 mg/g or 10000 μg/g. Pseudo second order reaction kinetics has provided a realistic description for removal of Cr(III) from solution with high correlation coefficient R² of (0.999). The adsorption isotherms were better described by the Freundlich equation (R² = 0.934). Adsorption of trivalent chromium ions onto selected material followed the pseudo second order model (R² = 0.996). Hence, the residual materials derived from the enrichment processes of quartz sand can be used as alternative adsorbent for the removal of trivalent chromium ions from aqueous solutions.

Effect of Operating Parameters on O3, O3/UV, O3/UV/PS Process Using Bubble Column Reactor for Degradation of Reactive Dyes

Effect of Operating Parameters on O3, O3/UV, O3/UV/PS Process Using Bubble Column Reactor for Degradation of Reactive Dyes

Study the Performance of a Dynamic Wall Heat Exchanger Using Computational Fluid Dynamics

Thermal systems in small devices like cooling electronic chips require efficient technologies with small diameter channels. These systems have laminar flow and disrupted boundary layers, leading to high pressure drop values. To ensure sufficient flow and limit coolant temperature, a possible solution is to dynamically deform one channel wall to mimic pumping and disrupt boundary layers, creating a peristaltic effect, called a dynamic heat exchanger. The aim of the present numerical study is to explore the effects of different operating parameters of the dynamic wall heat exchanger on the heat transfer performance. In our numerical study we varied different operating parameters (amplitude of vibration A, frequency f, minimum gap between upper and lower wall H and pressure difference P) and observed how it affects the performance of the dynamic wall heat exchanger in terms of mass flow rate of coolant (water) and heat transfer coefficient. A crucial finding is that the distribution of isotherms and streamlines is adequate, and heat transfer is significant when the relative amplitude is high. Additionally, this type of wall can generate substantial heat transfer even with minimal externally applied pressure.

Flash evaporation strategy of organic Rankine cycle for geothermal power performance enhancement: A case study

The performance of organic Rankine cycle (ORC) is poor due to the high irreversible losses in evaporator. To improve system performance, organic Rankine single flash cycle (ORSFC) and organic Rankine double flash cycle (ORDFC) are proposed, in which the traditional evaporation process is split into incomplete evaporation and flash evaporation. Thermal and exergetic efficiencies are taken as the objective functions, and the effects of the related operating parameters and the number of the flash stage on the thermodynamic performance of the system is conducted. The results show that for the ORSFC and ORDFC, in the direction of the rise of the heat source temperature, the net power output increases, the optimal evaporation temperature and flash temperature corresponding to different performance criteria also gradually increase. Besides, the dryness of the evaporator outlet is inversely proportional to the net power output, while it is directly proportional to the system efficiencies. When the dryness increases by 0.1, the net power output of the ORSFC and ORDFC decreases by an average of 148.5 kW, the thermal efficiency and exergetic efficiency of the ORSFC and ORDFC increase by an average of 0.56% and 1.37%, respectively. Moreover, with the flash stages increase, the performance criteria are improved at different magnitude. When a specific thermodynamic parameter is optimized, the ORDFC always obtains the best value for this parameter.

Xylitol biosynthesis enhancement by Candida tropicalis via medium, process parameter optimization, and co-substrate supplementation

The present study examines the impact of nitrogen sources (yeast extract, ammonium sulfate peptone, ammonium nitrate, urea, and sodium nitrate), salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, 0.3 g/L CaCl2), trace elements solution (0.1 g/L CuSO4, 0.1 g/L FeSO4, 0.02 g/L MnCl2, 0.02 g/L ZnSO4), operational parameters (temperature, aeration, agitation, initial pH and xylose concentration) and co- substrate supplementation (glucose, fructose, maltose, sucrose, and glycerol) on xylitol biosynthesis by Candida tropicalis ATCC 13803 using synthetic xylose. The significant medium components were identified using the Plackett Burman design followed by central composite designs to obtain the optimal concentration for the critical medium components in shaker flasks. Subsequently, the effect of operational parameters was examined using the One Factor At a Time method, followed by the impact of five co-substrates on xylitol biosynthesis in a 1 L bioreactor. The optimal media components and process parameters are as follows: peptone: 12.68 g/L, yeast extract: 6.62 g/L, salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, and 0.3 g/L CaCl2): 1.23 X (0.62 g/L, 0.62 g/L, and 0.37 g/L respectively), temperature: 30 °C, pH: 6, agitation: 400 rpm, aeration: 1 vvm, and xylose: 50 g/L. Optimization studies resulted in xylitol yield and productivity of 0.71 ± 0.004 g/g and 1.48 ± 0.018 g/L/h, respectively. Glycerol supplementation (2 g/L) further improved xylitol yield (0.83 ± 0.009 g/g) and productivity (1.87 ± 0.020 g/L/h) by 1.66 and 3.12 folds, respectively, higher than the unoptimized conditions thus exhibiting the potential of C. tropicalis ATCC 13803 being used for commercial xylitol production.

Effect of discrete inclined ribs on flow and heat transfer of supercritical R134a in a horizontal tube

In this work, discrete double inclined ribs (DDIR) are introduced into the horizontal flow of supercritical R134a to improve the thermal performance of vapor generators in the trans-critical Organic Ranke Cycle. Effects of operating and geometric parameters are investigated after model validation against experimental data. Results show that DDIR are adaptable to changes in operating conditions because spiral flow maintains the dominant position of forced convection heat transfer. DDIR enhance the PEC of horizontal ST by at least 70% and reduce circumferential thermal non-uniformity by up to 90%. Rib pitch has the most significant effect on heat transfer, followed by rib height and inclination angle. The optimal values for the three geometric parameters are 20 mm, 0.8 mm, and 60°. Finally, the mechanism of rib-induced enhancement is analyzed. Average heat transfer is improved by the strengthened mixing between bulk and near-wall fluid instead of suppressing the buoyancy effect. DDIR-induced enhancement is superior to subcritical cases owing to the integral effect of sharp variations in specific heat at supercritical conditions.