Initial Temperature Difference Research Articles

Investigation of the inlet useful temperature difference effect on the distribution of hydrodynamic characteristics of the vapor-liquid flow inside the falling-film evaporator heating tube designed for a nitric acid solutions evaporation

We present the results of mathematical modeling of effect of inlet useful temperature difference on the vapor- liquid flow in the heat exchange tube of a vertical evaporating film apparatus, which is designed for evaporation of nitric acid solutions. Distributions obtained along the heat exchange tube length of local values of the: mass flow rate of the fluid and secondary steam, the velocity of the fluid film, the velocity of the secondary steam, the Reynolds criterion of the liquid and vapor phases, the absolute pressure depending on the values of this useful temperature difference. The study was carried out using numerical simulation. To study the effect of the initial useful temperature difference on the hydrodynamics of the vapor-liquid flow, the vertical evaporator equipped with the tube ø38x3 mm and length of L = 4 m was adopted. The linear nature of the distribution of hydrodynamic parameters along the length of the heat exchange tube is established. The absolute pressure in the tube space decreases along the heating tube due to pressure drop. The limiting factor in reducing the absolute pressure is the friction losses of the secondary vapor on the solution film surface. A decrease in the pressure in the tube space leads to decrease in the boiling point of the solution. This leads to increase useful temperature. This has a positive effect on the evaporation efficiency The obtained data should be used in the design of evaporation plants, which are designed for evaporation of nitric acid solutions.

Inhomogeneous temperature in high temperature fluidized beds

In this work, we observe an inhomogeneous temperature distribution within a fluidized bed affects the mixing dynamics and therefore heat transfer performance. High temperature fluidized bed experiments with an initial temperature gradient are performed. As the superficial velocity increases, the bed becomes lightly fluidized. Despite fluidization, the bed temperatures do not converge, and the thermal gradients remain. Eventually the superficial velocity is sufficiently high to completely mix the bed and collapse the bed temperatures together. CFD-DEM coupled simulations are performed to investigate the mixing dynamics. Initial bed temperature differences of 100, 300, and 500 K are simulated with varying superficial velocities to create a regime map. At relatively low superficial velocities, the high temperature regions of the bed begin to bubble before the lower temperature regions due to gas density changes. To fully mix the particle temperatures in the vertical direction, the relative velocity (U/Umf) must be a minimum of 1.30.

Heat transport in a non-homothermal turbulent particle-laden flow in the collisional regime

In this investigation, we explore the impact of particle collisions on turbulent heat flux within a temporally developing thermal mixing layer arising from the interaction of two homothermal regions driven by a statistically homogeneous and isotropic velocity field. Employing two-way thermally coupled Eulerian-Lagrangian Direct Numerical Simulations (DNSs) at a Taylor microscale Reynolds number up to 124, we examine the influence of particle collisions for a Stokes number from 0.2 to 3, maintaining a fixed thermal to kinetic relaxation times ratio of 4.43. Our study quantifies the reduction in average heat transport induced by particle-to-particle collisions, which disrupt the temperature-velocity correlation created by the initial temperature difference. Notably, while collisions diminish this correlation, our analysis reveals their overall impact remains minor, even at the highest simulated Stokes number. Additionally, we present statistics of the temperature difference among colliding particles across various flow conditions.

Collisional cooling in confined gases at cryogenic temperatures: Time dependent near-wall accumulation and gas dynamics

The heat transfer characteristics of a confined gas are often quantified by anisotropic thermal conductivity and are affected by near-wall accumulation. However, in non-equilibrium conditions, where gas and walls are at different temperatures, transport coefficients, and state variables become dynamic, thus offering an interesting aspect of heat transfer, which is investigated in the present work. Here, we focus on the cooling of confined He by collisions with cold metal walls at cryogenic temperatures (30 - 150 K) in pristine and mixed states with a secondary gas at atmospheric pressure. The effects of wall temperature (Tw), type, and mass (m⁎) of the secondary gas on the cooling rate constant (k) and subsequently on the near-wall accumulation of He are investigated through non-equilibrium molecular dynamics simulations. The cooling curves of the confined gases are found to obey Newton's law of cooling. To probe the cooling process further, the temporal evolution of the near-wall accumulation is analyzed and found to be significant for lower Tw, which, in turn, promotes heat transfer at the interface through gas-wall and gas-gas collisions. In a gaseous mixture, such accumulations are found to be smaller for a heavier secondary gas, which leads to the inhibition of gas-wall collisions. Furthermore, the kinetic energy transfer between He and a considerably heavier gas particle is inefficient, resulting in the slower cooling of He, as observed in He-Ne and He-Ar mixtures. The quantity k is additionally affected by the interaction strength and thermal conductivity of the secondary gas, including the initial temperature difference between the wall and the gas (ΔT). The results of this study find their applications in the fields of microelectronics and microplasmas.

Quantification and correlation analysis of bubble characteristics and heat transfer performance in direct contact heat exchanger

In this work, a combination of morphological processing and watershed algorithm is proposed to measure bubble size, based on which an improved frame difference method is proposed to obtain bubble velocities with an F1 score of 0.96. Empirical equations for the boiling properties of flow in immiscible fluids and their influencing factors are developed. Correlation equations for the Nusselt (Nu) number and Colburn (j) factor are developed, with mean deviations of 5.42% and 5.47%, respectively. The results show that the increase in bubble rise rate and the trend of bubble growth become slower with the increase in the flow rate of the dispersed phase. In contrast, the temperature of the continuous phase has a negative correlation on the bubble growth and almost no effect on the bubble velocity. In addition, the heat transfer coefficient, which increases with the increase of the flow rate of the dispersed phase, has a negative correlation with the initial temperature difference. The main objective of this study is to provide a new method for measuring bubble parameters during direct contact boiling heat transfer and to provide new ideas for studying direct contact boiling heat transfer.

Rock damage evolution in the production process of the enhanced geothermal systems considering thermal-hydrological-mechanical and damage (THM-D)

Hot dry rocks (HDRs) geothermal relies mainly on enhanced geothermal systems (EGS) for production. During production, the evolution of rock stress distribution will cause damage to the rock, especially near fractures. The application of damage mechanics in the geothermal field has mostly focused on the process of hydraulic fracturing, with limited reports on damage research related to long-term water injection development. According to previous experimental studies, the effect of rock damage is significant and cannot be ignored. Therefore, based on a thermal-hydrological-mechanical and damage (THM-D) coupling model, it studies the rock damage evolution features and its role in changes in rock physical properties. It also analyzed the effects of the initial temperature, injection flow, fracture curvature/number, and stress difference on damage evolution. Results indicate that the damage area and degree continue to increase with time, but the growth rate becomes slower. There are two methods of damage evolution: the new damage caused by the expansion of the low-temperature region is throughout the process, and the original damage is aggravated in the later stages. Damage will cause changes such as reduced Young's modulus (negative feedback) and increased permeability (positive feedback) of the rock matrix, which in turn affect the damage evolution. More, damage increases with the initial rock temperature, injection mass flow, and stress difference increase, and the impact of the fracture curvature is small. The damage of complex fracture reservoirs is more pronounced than that of single fracture reservoirs. This study provides a tool for analyzing the impact of damage on the production performance of HDRs. The investigation of relevant patterns is expected to offer guidance for production strategies.

Heat transfer characteristics of oblique jet impingement liquid film cooling in the forced convection mode

Liquid film cooling by oblique jet impingement is widely used in small liquid rocket engine thermal protection. In this work, heat transfer characteristics of oblique jet impingement liquid film cooling in forced convective mode were experimentally investigated to examine the effect of the impingement velocity and the initial wall temperature. The temperature distribution on the rear surface (opposite to the jet) was recorded by a high-frequency infrared camera, and then the heat flux on the front surface was estimated by solving the inverse heat conduction problem. It was found that the lagging effect by thermal diffusion is nonnegligible and can be well described by the penetration time. In addition, thermal diffusion makes the temperature distribution on the rear surface more uniform than the liquid flow path. In contrast, the heat flux distribution has a clear boundary same as the liquid flow path. The length of the wetting front lwf can be fitted as lwf=atn. The constant a and the wetted area A are affected merely by the impingement velocity. The point with the maximum heat flux is located at the impingement point in the forced convective mode rather than the wetting front in the film boiling mode. Inside the liquid film, there is no clear boundary as the film thickness distribution between the thin layer zone and the raised zone, implying the local film velocity determines the heat transfer rather than the film thickness. The cooling power increases with higher impingement velocity and initial temperature difference. The standardization fitting equation shows the effect of the initial temperature difference on the cooling power is more significant than the impingement velocity.

Graphene coating reduces the heat transfer performance of water vapor condensation on copper surfaces: A molecular simulation study

Water vapor condensation is a key process for many applications. Existing studies in water vapor heterogeneous condensation have used different methods to modify the hydrophobicity of the water vapor condensation surface. One way to modify the surface properties is to use graphene coating. On a macroscale, surface modification using graphene coating can improve water vapor condensation heat transfer of various substrates. However, on the molecular scale, its effect is poorly understood. This work investigated the effect of graphene coating on water vapor condensation using molecular dynamics simulations (MDS). We examined the water vapor condensation on bare copper surfaces considering the effects of initial temperature difference, water model, and surface size, parameters that have not been investigated by previous studies employing MDS for the same water-surface configuration. One water model was then used to simulate the condensation on a copper surface with and without graphene coating. We then investigated the effect of graphene defect, the energy and vibration of graphene atoms, and the interaction between graphene and copper layers. The surface size notably influenced the condensation rate and heat transfer performance. The condensation rate and heat transfer performance were significantly reduced when the copper surface was coated by graphene. The number of water molecules condensed was 1253 molecules/ns on the bare copper surface, compared to 587 molecules/ns on the graphene-coated copper surface. Moreover, the water molecules condensed on the graphene-coated copper surface tended to return to the bulk vapor phase. Other important results are also provided. This study gives an insight into the water vapor condensation on graphene-coated copper surfaces, useful to pursuit the design and optimization of graphene-coated copper surfaces for applications that need efficient water vapor condensation, such as for industrial applications, like thermal, chemical, and nuclear.

Effect of ambient temperature and wind speed on horizontal flame spread and combustion trace on typical decorative wood boards

Decorative wood boards are common combustible materials and have been utilized in lots of buildings, which could bring serious property loss and casualties due to fires. In order to analyze fire hazard of decorative wood boards, horizontal flame spread characteristics and combustion traces were studied on six typical decorative wood boards though the tunnel furnace test in this paper. It was found that the flame spread distance of all the samples were in power function with time. With the increase of ambient temperature and ambient wind speed, the combustion was more intense, the crack length increased, the flame spread distance, and the flame spread rate (V) all increased, the cracks got wider, the micro appearance damage and the degree of carbonization got more serious. Among them, the relationship between V and the initial temperature difference (Tv-Ti) between solid pyrolysis temperature and the ambient temperature could be expressed as V∼(Tv-Ti)θ and the exponent of the power law θ was −6.24 for the decorative wood boards; the relationship between V and the ambient wind speed (U∞) could be expressed as V ∼ U∞δand δ was 9.0 for the decorative wood boards. In addition, the change rules of C, P and S elements on the combustion residues were similar, which were opposite to the change rule of O.

SiO2-Based Nanofluids for the Inhibition of Wax Precipitation in Production Pipelines.

Wax deposition in high-wax (waxy) crude oil has been an important challenge in the oil and gas industry due to the repercussions in flow assurance during oil extraction and transportation. However, the nanotechnology has emerged as a potential solution for the optimization of conventional wax removal and/or inhibition processes due to its exceptional performance in the alteration of wax morphology and co-crystallization behavior. In this sense, this study aims to study the performance of two commercial wax inhibitor treatments (WT1 and WT2) on the wax formation and crystallization due to the addition of SiO2 nanoparticles. Differential scanning calorimetry experiments and cold finger tests were carried out to study the effect of the WT on wax appearance temperature (WAT) and the wax inhibition efficiency (WIE) in a scenario with an initial temperature difference. In the first stage, the behavior of both WT in the inhibition of wax deposition was achieved, ranging in the concentration of the WT in the waxy crude (WC) oil from 5000 to 50,000 mg·L-1. Then, NanoWT was prepared by the addition of SiO2 nanoparticles on WT1 and WT2 for concentrations between 1000 and 500 mg·L-1, and the performance of the prepared NanoWT was studied at the best concentration of WIT in the absence of nanoparticles. Finally, the role of the nanofluid concentration in wax inhibition was accomplished for the best NanoWT. Selected NanoWT with nanoparticle dosage of 100 mg·L-1 added to WC oil at 5000 mg·L-1 displays reductions in WAT and WIE of 15.3 and 71.6 for NanoWT1 and -2.2 and 42.5% for NanoWT2. In flow loop experiments for the crude oil at temperatures above (30 °C) and below (16 °C), the WAT value indicates an increase of 8.3 times the pressure drops when the crude oil is flowing at a temperature below the WAT value. Therefore, when NanoWT1 is added to the crude oil, a reduction of 31.8% was found in the pressure drop in comparison with the scenario below the WAT value, ensuring the flow assurance in the pipeline in an unfavorable environment. Based on the pressure-drop method, a reduction greater than 5% in the wax deposit thickness confirms the wax deposition inhibitory character of the designed NanoWT.

Effect of pressure on regenerative cooling process of endothermic hydrocarbon fuel at severe pyrolysis conditions

Regenerative cooling technology with supercritical aviation kerosene as coolant is the optimal thermal management method for advanced aero engines. In order to fill the gap in existing research on the pressure effects at severe pyrolysis, the influence of pressure on the flow field, pyrolysis behaviours, heat transfer, and surface coking are numerically investigated in this study. The results indicate that the velocity-temperature curves at different pressures have two intersections due to the difference in initial pyrolysis temperature, reaction rate, and product distribution. Fuel pyrolysis more easily occurs at high pressure, and elevating pressure improves the fuel heat sink. Besides, a special deterioration of heat transfer is found at high conversion rates because of the combined contribution of weakened primary endothermic reaction and enhanced secondary exothermic reaction. Heat transfer deterioration is delayed at 3.5 MPa due to the high initial pyrolysis temperature and significant flow acceleration. The primary pyrolysis reaction provides more than 80% chemical heat sink and 60% flow acceleration at fully cracked conditions at 5.0 MPa. In addition, inhibiting catalytic coking is the principal method to reduce carbon deposition, and more attention should be paid to carbon deposition under high pressure. The results obtained in this study are expected to provide insights into the selection of operating pressures for advanced aero engines.

Numerical Simulation on Enhanced Heat Transfer and Flow Characteristics in Direct-Contact Heat Exchanger: A Novel Kenics Static Mixer

In this paper, a novel Kenics static mixer applied in a direct-contact heat exchanger (DCHE) was proposed in order to enhance the heat transfer efficiency. The computational fluid dynamics (CFD) simulation method was adopted to investigate the effect of the continuous phase and dispersed phase on direct-contact heat transfer (DCHT) in the Kenics static mixer. The perforation index (PI) was introduced to depict the performance of the Kenics static mixer, and the effect of different numbers of openings at three initial heat transfer temperature differences (at the inlet of the continuous and dispersed phases) was studied. The simulation results showed that under the same working conditions, a larger initial temperature difference would result in greater differences in the fluid uniformity index (UI), turbulence intensity, and time evolution of a gaseous working substance. The increase of hole numbers and decrease of hole diameters can optimize the DCHT. Under three initial temperature differences, the heat transfer efficiency for the 6-hole and 9-hole Kenics DCHEs was about 20% higher than the Kenics DCHE without holes.

PCM-based ceiling panels for passive cooling in buildings: A CFD modelling

To relieve the upsurge of the energy demand associated to building indoor cooling, passive cooling employing phase change materials (PCMs) has been proposed as a promising technique to stabilise indoor air temperature fluctuation and reduce building energy demand. PCMs can exchange a large amount of latent heat during the melting and solidification processes, which can be utilised in line with the discharging and charging processes of a cooling system. The use of encapsulated PCM ceiling panels in buildings has immense application potential for passive cooling, which has attracted investigations in recent years. The geometry selection of the PCM ceiling panel is vital as it determines the exposed surface area to the surrounding air and the natural convection, and therefore the heat transfer rate to/from the PCM, which generally suffers from low thermal conductivity. This paper builds on the geometric optimisation of enclosed PCM capsules driven by natural convection, aiming to investigate the phase change behaviour and thermal performance of encapsulated PCM ceiling panels of different geometries. Here, the presented study focuses on the conjugate heat transfer phenomena through the surrounding air, panel shell, and PCM. A mixture of lauric, capric, and oleic acids was selected as PCM encapsulated in a thin-shell enclosure made of acrylonitrile butadiene styrene plastic, which forms the aesthetic panels attached to the ceiling. A computational fluid dynamics model was validated using full-scale experimental data and further employed to analyse the discharging process and design considerations of the PCM ceiling panels. The effects of various influencing factors were explored, such as panel volume, the initial temperature difference between PCMs and surrounding air, shell thickness, and geometrical features. The results indicate that the panel comprised of a pyramid array is more advantageous than the tetrahedral-based panel in terms of thermal performance, where the average melting rate is 20.8 % higher when the panel volume is 250 mL. In addition, tweaking the geometric features of the panel will largely impact its thermal performance as the effective heat transfer area and natural convection conditions are varied. Finally, it was found that hanging the panel to the ceiling will effectively enhance the heat transfer compared to directly attaching it to the ceiling. The results complement the knowledge body of macro-encapsulated PCM ceiling panels in terms of thermal performance and geometric optimisation. The effects of geometric features on the thermal performance of the PCM ceiling panels are studied in a more holistic manner.

Algorithm for calculating the criterion for the temperature-dynamic characteristics of the cooling system of tractor and car engines

The article provides information on the temperature-dynamic qualities of the cooling system for tractor and car engines. A parameter that determines the efficiency of the cooling system. Definitions of the criterion of temperature-dynamic characteristics. Calculation algorithm for determining the initial temperature difference. The results of the calculated and experimental data of the temperature-dynamic characteristics of the cooling system of the UAZ-469 car and the TTZ-80 tractor.

Investigation on local geothermal energy attenuation after long-term operation of ground heat exchanger with considering aquifer effect

The long-term operation of deep buried ground heat exchangers (GHE) for heat extraction would attenuate the local geothermal field. The variation of geothermal energy in the affected area over time is a subject worthy of dedicated study. In this paper, the heat transfer between GHE and surrounding geological strata including aquifuge and aquifer layers is modeled and numerically solved to investigate the variations of GHE performance and attenuation behaviors of ground temperature field. The results show that the reduction ratios of GHE performance in the aquifer and aquifuge layers between 1st and 8th years are 1.3% and 8.9%, respectively, due to the convective heat transfer induced by groundwater in the aquifer layer. The analysis of local temperature variation implies that the groundwater flow leads to the circumferential asymmetry of ground temperature reduction in aquifer layer, which also affects the temperature distribution in geological layers adjacent to the aquifer. The worst ground temperature recovery point appears on the borehole wall in the aquifuge layer, while it appears at a fixed position downstream in the aquifer layer. Taking the ground transient and initial temperature difference greater than 0.5°C as the threshold to characterize the attenuation region, the geothermal field attenuation area of the eighth year in the aquifer is about 4.5 times that of the first year, while it is about 5.1 ∼ 5.5 times that of the first year in the aquifuge layers. The analysis of variations of GHE performance and ground temperature field quantitatively evaluates geothermal attenuation behaviors in aquifer and aquifuge layers subject to the long-term operation of GHEs.

A Multi-Objective Comprehensive Evaluation of Heat Transfer Performance of a Direct-Contact Heat Exchanger

Abstract Direct-contact heat exchangers have great potential for waste-heat utilization. This study established a multi-objective evaluation model of the volumetric heat-transfer coefficient, entransy dissipation, and uniformity of the temperature difference field of the direct-contact heat exchanger. The optimal operating parameters for the heat exchanger were obtained by experimentally investigating the relationship between the operating parameters and the volumetric heat-transfer coefficient, entransy dissipation, and uniformity of the temperature difference field. The results indicated that the smaller the entransy, the greater the effectiveness of the heat exchanger in the direct-contact heat exchanger. The results also indicated that the volumetric heat-transfer coefficient increased with the increase in the flowrate ratio and initial temperature difference. The study found that entransy demonstrated the smallest dissipation and the largest effectiveness of the heat exchanger when the initial temperature difference was 120 °C and the flow ratio was 6:1. This study has guiding significance for the optimal design of direct-contact heat exchangers.

Experimental and numerical investigation of heat transfer by water spray injection into pressurized gas atmospheres

Better realization of isothermal changes of state can be seen as a decisive general prerequisite for the improvement of reachable overall efficiencies of compressors, power plants or Stirling engines. The injection of water during a compression or expansion stroke is a promising method for approximating isothermal change of state, as there is a big potential of high heat transfer rates in comparison to traditional cooling and heating methods through walls. Water injection into atmospheres of nitrogen and helium up to 18 bar is investigated in an experimental setup varying initial temperature difference between injected water and gas temperatures and by varying the injection pressure, injection time or the gas type. It is shown that thermal resistance remains relatively independent of the temperature difference but strongly depends on the injection pressure difference. Transferred heat and heat flow rise with the pressure of the gas atmospheres. Numerical simulations are conducted along an expansion stroke and lead to the result that the delivered work can reach 94.2% of the isothermal course. By water injection with preheated water with a low initial temperature difference of 55 K, the expansion can deliver the same amount or even higher amount of work as the isothermal case. • Water spray injection in nitrogen and helium atmospheres pressurized up to 18 bar. • New calculation method of thermal resistances during spray injection. • Injection pressure has the highest impact on thermal resistance. • Monatomic gas helium is favourable compared to diatomic gas nitrogen. • Simulations of expansion with water injection get close to an isothermal curve.

Orientation impact on structural integrity of a shell and tube latent heat thermal energy storage system

Latent heat thermal energy storage systems can regulate the intermittency of electricity generation in a grid powered by renewable energy sources. Such systems could be used in conjunction with Brayton power generation cycles operating at high temperatures (520 °C–750 °C) delivering higher efficiency. However, a trade-off of higher thermal efficiency can be higher thermal stresses. The isothermal latent heat thermal energy storage and release can reduce the thermal stresses for a specific design. This study investigates the impact of the orientation on the melting process and the consequent thermal stresses in a lab-scale latent heat shell and tube system using a combination of transient computational fluid dynamics and finite element analyses. With a high temperature phase change material melting at 705.8°C, two initial temperatures of 700°C and 650°C were considered in transient analyses, leading to a 50 K and 100 K initial temperature difference across the tubes, respectively. For the structural analysis, an elastic method was employed for the condition of 50 K temperature difference, and an elastic-plastic analysis for the condition of 100 K to account for plastic deformation. The results of the elastic analysis presented the maximum thermal stresses of 63.5 MPa and 106.7 MPa in tubes in the horizontal and vertical orientations, respectively. The stress in the tube sheet was slightly higher (94.5 MPa) for the horizontal system compared with 90.4 MPa in the vertical position. For the condition of 100 K, the results of the elastic-plastic analysis identified the highest stresses of 172.5 MPa and 147.4 MPa in the tube sheets of the horizontal and vertical systems, respectively. For both initial temperature conditions, the stress level in tubes is lower in the horizontal orientation, which is where most cost occurs in a shell and tube system. Particularly important for the 100 K condition, the results show a lower stress of 100 MPa in tubes for a horizontal system compared with 140 MPa in a vertical orientation. In general, the lowest thermal stress occurs where a melt layer forms around tubes during the early stages of a melting process. A higher stress occurred in parts in contact with argon. The highest level of stress occurred in parts in contact with solid PCM, which has direct implications for larger vessel designs. This study provides insights into hydrothermal and mechanical design of a PCM system to prevent and/or manage localised maximum thermal stresses for a cost-effective thermal energy storage system.

The degradation of Fenuron in water by activated persulfate oxidation: An analysis of efficiency, influential parameters and potential applicability

Fenuron (FEN), a member of phenylurea herbicides can be regarded as water contaminant due to its persistence in environment. Persulfate (PS) oxidation as a highly effective degradation technique was applied to degrade FEN using ferrous sulfate (FeSO4), pyrite (PyR; FeS2) and zero-valent iron (ZVI) to activate PS. The systems’ efficiency followed the order as: ZVI-PS system > PyR-PS system > FeSO4-PS system; where, respective degradation of 0.12 mmol/L FEN was 97.5%, 63.6% and 57.8% after 60 min. Therefore, ZVI-PS system was chosen for subsequent detailed analysis and the effects of several influential parameters including ZVI dosage, PS concentration, initial pH, FEN concentration and initial temperature were examined via kinetic studies. ZVI-PS system induced more than 85.0% degradation of 0.06–0.24 mmol/L FEN at initial pH 2.52 to 9.0. Further, difference in initial temperature had an insignificant effect on degradation. ZVI-PS system induced FEN mineralization of about 86.0% after 360 min. Electron paramagnetic resonance (EPR) analysis and free radical quenching (FRQ) analysis were used to demonstrate degradation mechanism by ZVI-PS system. EPR analysis supported that sulfate (SO4−) as well as hydroxyl (OH) radicals were generated in ZVI-PS system; however, FRQ analysis showed that SO4− was dominant reactive radical to carry out FEN degradation. The degradation efficiency of ZVI-PS system was found higher in real waters, which shows its potent applicability to degrade FEN in field. The study concludes that ZVI-PS system can efficiently degrade FEN and may contribute as basic information for future research for the removal of phenylurea herbicides.

RETRACTED ARTICLE: Effect of cooling process on reducing residual stress of hot rolled high strength strip

ABSTRACT In order to analyse the influence of different laminar cooling technology on residual stress of steel strip, a finite-element model of strip was established with ABAQUS and FORTRAN named basic model. The evolution of temperature, phase transformation and stress of the strip during cooling process were expressed with coupling calculation. Other four finite-element models were established based on the basic model by changing its initial condition and boundary condition. The new models represented four cooling technology named edge masking, sparse cooling, posterior cooling and initial transverse temperature difference controlling. The results show that the stress distribution on strips tends to be high compressive stress on edge and tensile stress on middle section. The effect of the four cooling technologies on the residual stress reduction is ranked as initial transverse temperature difference controlling, sparse cooling, edge masking and posterior cooling.