Non-uniform Heat Distribution Research Articles

Identifying untraced faults associated with high return temperatures from heating systems in buildings connected to district heating networks

The district heating (DH) system is in its transition towards the 4th generation district heating (4GDH), and the high DH return temperatures need to be addressed during the process. In the existing building heating systems, many faults, malfunctions, or sub-optimal operations can lead to high DH return temperatures. However, the field of fault detection and diagnostics (FDD) within heating systems is notably under-researched in contrast to their counterparts in ventilation and air conditioning in building HVAC systems. This divergence can be attributed to several factors, including limited digital integration, a scarcity of data, and the non-obvious nature of faults in heating systems. In this study, we utilized heat cost allocators (HCA) and energy meters to investigate the features and potential impacts of four untraced faults that can lead to high district heating (DH) return temperatures in both space heating and domestic hot water systems in large buildings. We identified component-level faults, including heat exchanger overflow, space heating temperature controller failures, and excessive operating temperatures due to bypass, as well as system-level issues such as non-uniform heat distribution in buildings and its impacts. This exploration provides new, critical insights for advancing FDD research in HVAC and DH systems.

Temperature prediction of submerged arc furnace in ironmaking industry based on residual spatial-temporal convolutional neural network

The submerged arc furnace is widely regarded as one of the most promising ore smelting technologies. However, the real-time monitoring of the multiple physical fields including electric, thermal, and mas, through computational fluid dynamics demands significant computational resources. This paper introduces the spatial-temporal convolutional neural network algorithm to address this challenge. Initially, the influences of various working conditions on these physical fields are analyzed. Subsequently, a prediction model is developed based on the coupling of these multiple physical fields model. The spatial-temporal convolutional neural network algorithm is then employed to elucidate the main parameter distributions, enabling the automatic real-time detection of temperature variation trends and providing a theoretical foundation for intelligent furnace operation. The findings indicate that the electric field is the predominant factor causing non-uniform heat distribution, with localized overheating primarily occurring at the electrode ends. The application of the proposed model facilitates dynamic prediction of the temperature distribution, establishing relationships between historical and future time steps as well as local and global temperature variations. The reliability of the temperature prediction model is confirmed, with the model achieving an accuracy of 99.76 %, surpassing the 98.18 % accuracy of the traditional multi-layer perceptron model.

Symmetry‐based analysis of nonlinear mixed convection in 3D EMHD nano‐Carreau fluid flow with Riga stretched surface effects and multi‐physical interactions

AbstractThis study presents a comprehensive investigation into the dynamics of an electrically magneto‐hydrodynamic (EMHD) nano‐Carreau fluid under nonlinear mixed convection. We develop a 3D steady‐state framework that incorporates various influential factors such as nonuniform heat source‐sink terms, nonlinear thermal radiation, Joule heating, and chemical reactions, along with the effects of a Riga stretched surface. Through rigorous analysis, we explore the impact of thermophoretic and Brownian motions on flow patterns and stagnation point velocities. Our study encompasses scenarios involving a Riga stretching sheet, EMHD phenomena, porous media, suction‐injection processes, and diverse slip conditions (momentum, heat, volume fractions), in conjunction with chemical reactions. By employing symmetry transformations, we transform complex partial differential equations (PDEs) into more manageable ordinary differential equations (ODEs), facilitating effective numerical solutions using the Lobatto IIIa bvp4c method in Matlab. The findings are presented through detailed graphical representations and comparative tables. Key findings include the observation that elevated Hartmann numbers contribute to reduced velocity yet enhanced temperature profiles, influenced by factors such as nonuniform heat distribution, thermal radiation, and viscous dissipation. Additionally, concentration profiles exhibit a diminishing trend with increased Lewis numbers, chemical reactions, and specific slip parameters.

Study of the adsorption mechanism of certain dyes from wastewater on commercial activated carbon using the Langmuir and Freundlich methods

In today's society, there is significant emphasis on environmental protection, with research focused on reducing pollution and developing effective depollution techniques. A growing concern is the presence of colored discharges in wastewater, which contain high levels of toxic substances that pose substantial risks to ecosystems. To mitigate these risks, various methods are employed to remove pollutants from industrial effluents, with adsorption being one of the most effective. Among the adsorbents used, activated carbon is the most commonly utilized due to its high surface area and adsorption capacity. This study aims to enhance the understanding of how two organic dyes, Methyl Red and Methylene Blue, can be removed from aqueous media through adsorption onto commercial activated carbon. The adsorption kinetics and isotherms were employed to elucidate the mechanisms involved in the elimination of these dyes from water. The kinetics were investigated using a stirred reactor, with experiments designed to vary parameters such as the initial dye concentration, the mass of the adsorbent, and the contact time. The experimental data were modeled using kinetic equations of first and second order. The results indicated that the adsorption of both Methyl Red and Methylene Blue onto activated carbon followed a pseudo-second-order kinetic model, as evidenced by large regression coefficients, signifying a good fit. This suggests that the adsorption process is likely controlled by chemisorption, involving valency forces through sharing or exchange of electrons between adsorbent and adsorbate. Additionally, the adsorption isotherms were analyzed to further understand the adsorption mechanisms and capacity. The results showed that the adsorption of both dyes onto commercial activated carbon conformed well to the Freundlich isotherm model. This model implies that adsorption occurs on a heterogeneous surface with a non-uniform distribution of adsorption heat over the surface. Overall, this study provides valuable insights into the adsorption behavior of Methyl Red and Methylene Blue on activated carbon, highlighting the effectiveness of this adsorbent in removing organic dyes from wastewater. The findings underscore the potential of using commercial activated carbon in the treatment of industrial effluents, contributing to the development of more efficient and sustainable water purification methods.

Application of acoustic vibration promotes heat transfer of high-viscosity fluid in a container

The inferior fluidity of high-viscosity liquids hinders their efficacy in heat transfer, resulting in non-uniform heat distribution and occasional overheating, which significantly impairs process and product quality. In this study, we aim to investigate the effect of acoustic vibrations on heat transfer in sealed containers containing high-viscosity fluids by employing computational fluid dynamics (CFD). We established a VOF model and validated it through experiments. Through the collaborative analysis of the velocity field and temperature field, the mechanism of vibration-enhanced heat transfer was revealed. The results of the study indicate that acoustic vibration can enhance convective flow and improve field synergy between the temperature and velocity fields, leading to improved temperature uniformity and heat transfer efficiency. Heat transfer efficiency shows a positive correlation with vibration frequency and amplitude, though no significant correspondence is found with vibration acceleration. Within a certain range, the heat transfer efficiency is more sensitive to the changes in low amplitude or the changes in high frequency. Within a certain range of acceleration, large amplitude with low frequency has a better effect on heat transfer. Finally, we developed a functional relationship between heat transfer efficiency and vibration parameters to predict the heat transfer effect under different parameters, providing suggestions for specific process optimization.

Efficient energy valley optimization approach for reconfiguring thermoelectric generator system under non-uniform heat distribution

A thermoelectric generator (TEG) suffers from low conversion efficiency, especially when it has been operated under non-uniform temperature distribution. Dynamic reconfiguration is an effective method to enhance the TEG overall efficiency although it requires many electrical switches that make the process more complex. This paper proposes a new approach of energy valley optimizer (EVO) to optimally reconfigure the TEG array operated at non-uniform temperature distribution and enhance the harvested electrical energy. The selection of EVO is due to fast convergence rate, parameter-free, and avoiding stuck in local optima. Minimization of absolute error between the TEG system current at maximum power and the actual one is the proposed fitness function. The analysis is performed on small 9 × 9 TEG array and large 15 × 15 TEG array. Eight temperature distribution patterns of non-uniform row, non-uniform column, short wide, long wide, diagonal, external, internal, and random are analyzed. The proposed EVO is assessed via comparing to reported immune genetic algorithm (IIGA) and other programmed approaches of osprey optimization algorithm (OOA), chef-based optimization algorithm (CBOA), artificial hummingbird algorithm (AHA), and northern goshawk optimizer (NGO). Moreover, statistical investigation is implemented via performing Kruskal-Wallis test, Friedman test, ANOVA test, and Wilcoxon rank test. The fetched results revealed that, the best enhanced power from small 9 × 9 array is 9.143% compared to the original arrangement occurred at long wide temperature distribution. Regarding large 15 × 15 TEG array, the best enhanced power happened during diagonal pattern with 3.359%. The results confirmed the preference of the proposed EVO in solving the TEG system reconfiguration problem with great efficiency.

An efficient artificial gorilla troops optimizer-based tracker for harvesting maximum power from thermoelectric generation system

The thermoelectric generator (TEG) device opens a new lighted avenue for saving waste heat by transferring it into electrical energy. Due to the unique features of the TEG systems, they have materialized as promising alternatives for green power production. Nonetheless, the TEG generated power is mainly influenced by the distribution of temperature levels added to the value of the load. To enhance the utilization efficiency of the TEG, proposing a reliable maximum power point tracker (MPPT) approach to detect the maximum global power of it is an essential solution. Two remarkable drawbacks are detected in the conventional MPPT, low dynamic response and high oscillations around MPP. Also, operating the TEG system at non-uniform heat distribution generates multi-local peaks in the TEG system characteristic which is difficult to be monitored by traditional trackers. Therefore, this paper proposes an efficient artificial gorilla troops optimizer (GTO) to simulate MPPT with TEG array operated at various temperature distribution conditions. The proposed approach is examined on 9 × 9 and 15 × 15 TEG arrays operated at seven cases including normal, non-uniform row, non-uniform column, long wide, diagonal, internal, and random temperature distributions. For investigating the proposed approach performance versus the state-of-the-art techniques, set of MPPT approaches including comparison to incremental resistance (INR), particle swarm optimizer (PSO), seagull optimization algorithm (SOA), and cuckoo search (CS) have been implemented under the same case studies. The comparisons reveal the superiority of the proposed GTO-MPPT in monitoring the peak global harvested power in time less than 1 s. The SOA is located at the second rank after GTO in the fetched power and the time consumed for achieving the steady state operation. Meanwhile, the INR, PSO, and CS fall in local maximum power points. Moreover, for 9 × 9 array, the minimum error between the simulink model and the proposed GTO-MPPT is 0.01% at internal heat distribution pattern while it is 0.09% for 15 × 15 array at normal operation. The results proved the efficiency of employing the GTO-MPPT compared to the other considered methods.

Study on the uneven flow distribution and non-uniform heat transfer in microchannels

The power module is one of the main heating sources with non-uniform heat flux in high-power electrical servo systems used for flight vehicles. Faults in the power module are usually caused by a high or a non-uniform temperature. Given the environment of heat dissipation during flight, a regenerative cooling method is typically used, and the cooling system is designed as a microchannel heat sink with supercritical fuel. This is an effective means of solving thermal problems in the flight vehicles. However, because of the high heating power and non-uniform heat distribution of the power module, it is necessary to optimize its heat sink to restrict the high temperature rise and suppress the non-uniform distribution of temperature. In light of these considerations, a 3D numerical model of the microchannel heat sink of a power module with non-uniform heat flux was established in this study to examine the heat transfer and the thermal performance of the cooling channels. Based on the validation of the mesh and numerical method, the simulations of the flow distributions of the channels were performed to assess the thermal performance of the heat sink. It included investigating the effects of the inlet location of the manifold and its injection angle on the flow distribution in the channels, and the influences of the flow distribution and the operational parameters on the thermal performance of the heat sink. The results revealed that the Z30 configuration provided the best location and injection angle of the inlet to match the non-uniform heat flux of the power module. In this case, the values of Stanton number and buoyancy parameter of channel 4 yielded the minimum values of all channels owing to its higher flow rate and gradual rise in temperature. The deviation in the rate of mass flow Φ changed slightly corresponding to the various operational parameters, only the total heat flux would bring a bigger fluctuation. The tiny difference in temperatures among the observation areas on the substrate verified the positive influence of the flow distribution in matching the non-uniform heat flux.

Friction riveting of FR4 substrates for printed circuit boards: Influence of process parameters on process temperature development and joint properties

This work investigates the influence of Friction Riveting processing conditions on FR4-PCB substrate/AA2024 rivet joints in terms of process temperature evolution, joint formation, and joint physical-chemical and mechanical properties. The joints were manufactured using 4 mm diameter AA-2024-T3 rivets and FR4 laminates of 1.5 mm thickness with single or double copper-clad layers. The evolution of process temperature evolution was recorded on the FR4 substrate surface and correlated with the resulting joint formation. Most joints obtained with double copper clad layers developed process temperatures above 300 °C, whereas joints produced with a single copper clad presented slightly lower temperatures, but still above 250 °C. Rivet anchoring was achieved for both FR4 material combinations in the configuration of a single-base laminate, as well as two and even three overlapped laminates. Thermogravimetric analyses revealed that above 300 °C intensive thermal degradation occurs on FR4 materials (with 30% mass change), followed by decomposition, resulting in non-uniform heat distribution throughout the thickness. The joint ultimate tensile force was higher for double copper-clad layers and the joints achieved within more than one laminate, showing higher anchoring efficiency.

Time-dependent behavior of full-scale precast post-tensioned (PCPT) girders: Experimental and finite element analysis

Excessive volumetric changes associated with shrinkage and non-uniform moisture and heat distribution along long-span girders induce unwanted curvatures. This study aims at investigating both short- and long-term measurements of various quantities involving midspan deflections, tendon strains, longitudinal steel bar strains, concrete strains, and thermal changes in precast-post-tensioned (PCPT) girders. A total of 2 PCPT girders were cast in this study with symmetrical structural and geometrical details. Post-tensioning of the first and second girders was performed on the 28th and 120th days of their casting, respectively. Long-term measurement was performed on the first girder. It was observed that all measured parameters increased swiftly during post-tensioning. During the initial 30 days after post-tensioning, a gradual increase in all parameters was observed, whereas all measured parameters exhibited negligible increase beyond that. A Finite Element Model was generated using ATENA to estimate short-term deflections of PCPT girders during post-tensioning. In general, a good agreement between experimental and analytical midspan deflections was observed.

Effect of post welding heat treatment on the weld quality of micro plasma arc welded SS-316L thin sheet

High thermal gradient formed during the fusion welding process results in development of undesirable residual stress in the weldments. This stress is developed due to restraint by the parent metal during weld solidification. The high heat input results in non-uniform heat distribution across the weld region in other words non-uniform microstructural development across the weld region and hence the mechanical properties of the joint are often not uniform. In order to avoid inhomogeneity in the mechanical properties and also to reduce/eliminate undesirable residual stress, the welded samples are given post welding heat treatment. In this research, 500 µm thin SS-316L sheets are welded using micro plasma arc welding process and then the welded specimens are heat treated. The welding experiments are conducted by varying welding speed, welding current and stand-off distance. Weld bead microstructure, micro-hardness, ultimate tensile strength (UTS), yield strength and percentage elongation are determined before and after heat treatment. The effects of welding heat input and process parameters on the measured weld qualities are studied. Analysis of variance is also performed to estimate the influence of factors and their interaction on the weld quality. The post weld heat treatment results in an increase in the grain size of the HAZ and is found in the range of 38.96 µm to 56.22 µm whereas for as-welded samples it is in the range of 29.88 µm to 50.40 µm. The average UTS value of the heat treated samples is increased by 9.9% compared to the as-welded samples. The hardness of the fusion zone varies in the range of 175-215 HV.

Optimal Control of Centralized Thermoelectric Generation System under Nonuniform Temperature Distribution Using Barnacles Mating Optimization Algorithm

The need for renewable energy resources is ever-increasing due to the concern for environmental issues associated with fossil fuels. Low-cost high-power-density manufacturing techniques for the thermoelectric generators (TEG) have added to the technoeconomic feasibility of the TEG systems as an effective power generation system in heat recovery, cooling, electricity, and engine-efficiency applications. The environment-dependent factors such as the nonuniform distribution of heat, damage to the heat-transfer coating between sinks and sources, and mechanical faults create nonuniform current generation and impedance mismatch causing power loss. As a solution to this nonlinear multisolution problem, an improved MPPT control is presented, which utilizes the improvised barnacle mating optimization (BMO). The case studies are formulated to gauge the performance of the proposed BMP MPPT control under nonuniform temperature distribution. The results are compared to the grey wolf optimization (GWO), particle swarm optimization (PSO), and cuckoo search (CS) algorithm. Faster global maximum power point tracking (GMPP) within 381 ms, higher power tracking efficiency of up to 99.93%, and least oscillation ≈0.8 W are achieved by the proposed BMO with the highest energy harvest on average. The statistical analysis further solidifies the better performance of the proposed controller with the least root mean square error (RMSE), RE, and highest SR.

Investigation of the effect of non-uniform heat distribution of microwave on the mortality rates of some plants

Weeds, cause significant losses in agricultural production and are mostly controlled by herbicides, which are harmful to the environment. An alternative method that can be applied instead of these chemicals that pollute the soil and water is the microwave weed control method. But, one of the main problems with the microwave weed control method is the non-uniform heat distribution. This study aims to investigate the effect of non-uniform heat distribution on the mortality rate in the microwave weed control method by the NDVI (Normalized Difference Vegetation Index) technique. The NDVI technique has been used for the first time in this study to determine the mortality rate in microwave weed control. Mortality rates in one-week germinated Lepidium sativum (cress) and Hordeum vulgare (barley) grasses that were exposed to microwave energy for 10, 20, and 30 seconds were measured. It was determined that a higher rate of mortality occurred in the uniform heat distribution condition, compared to the non-uniform heat distribution (p <0.05). Mortality rates in both Hordeum vulgare (barley) and Lepidium sativum (cress) grasses increased as the microwave application time increased. The highest mortality rate occurred in Lepidium sativum (cress) grass (69.81%) and Hordeum vulgare (barley) grass (61.01%) with uniform heat distribution for 30 seconds. In the non-uniform heat distribution for 10 seconds, an increase was observed in Hordeum vulgare (barley) grass compared to the control group (7.01%). As a result, it can be said that weed control with microwave energy has the potential to be a good “environmentally friendly alternative method” to chemical weed control methods.

Enhanced power extraction from thermoelectric generators considering non-uniform heat distribution

In this paper, a technique to enhance the performances of the thermoelectric generator under non-uniform heat distribution is developed. A large area of heat source is needed when the thermoelectric generator is used for high power applications such as powering air conditioners, household appliances, and distributed generation systems. Non-uniform heat distribution is a natural phenomenon in large surface of heat source. A model was developed and was validated with a prototype of thermoelectric panel 80 V, 2 A. Results show very good similarities between the model and the prototype outputs under various operating conditions. The error during the tests for the voltage performances was 6.5%, while the current was 1.1%. A method of maximizing power, i.e., developing a specialized maximum power point tracker (MPPT) along with blocking diodes, is proposed to overcome the effects of non-uniform heat distribution. In a typical condition, the output power dropped by 30% when a non-uniform thermal distribution is imposed to the array. The blocking diode can save power by 15%, and the MPPT expands up to 20% power when adopting this method.

Performance analysis of thermoelectric generator implemented on non-uniform heat distribution of photovoltaic module

PV–TEG hybrid system is widely discussed nowadays, as an alternative way to maximize solar radiation energy which is from both of its light and heat. In recent years, the idea of using thermoelectric generators (TEGs) to extract energy from heat waste has increased with applications varying from milliwatts to kilowatts. To form a circuit, numbers of TEG modules can be connected in series and/or parallel configuration to produce the required voltage and/or current. In the PV–TEG systems, due to operating environments, each TEG module’s power generation is subject to temperature mismatch. There is also considerable variability in the electro-thermal output and mounting pressure of each TEG module in a circuit, resulting in a significant inconsistency. Therefore, when each TEG in the array is active, a varying electrical operating point will occur at which peak energy can be obtained and problems with lower power output will occur. In this work, an individual TEG module test method was used to measure and analyze data from specific types of TEG, and a record of the maximum power output under different temperature variations is obtained. Then, the performance of the TEG system is measured and evaluated with a test bench where the modules are attached at different backside areas of generic PV panels. The non-uniform heat distribution condition created in the experiment showed an average 33 % drop in power production from the maximum power that would be available in case each TE series circuit operates under uniform heat distribution. This experimental finding demonstrates the problem and the outcomes discussed in this paper validated a thorough examination of the effect of nonuniform operating temperatures on a range of thermoelectric generator’s energy output.

Improving the local thermal conductivity of flexible films by microchannels filled with graphene

Low thermal conductivity is an outstanding problem that hinders the application of polymer substrates in flexible devices. Incorporating high thermal conductivity fillers into polymer to enhance its thermal conductivity usually requires a large mass fraction of fillers at the expense of the flexibility and the insulation capabilities of polymer substrates. The non-uniform heat distribution in flexible devices allows for improving the local thermal conductivity of the core areas via microchannels, a strategy which is an effective method in thermal engineering and can be well designed to adapt to large deformation of flexible devices. Here, we report the fabrication of microchannels in polyimide (PI) composite film by oxygen plasma etching and subsequent filling the microchannels with graphene. Utilizing the time-domain thermoreflectance method and the finite element method, we confirmed that the local thermal conductivity of graphene-filled region is about 10 times larger than that of the unfilled region, which is comparable to that of the PI composite filled heavily with traditional high thermal conductive fillers. In addition, it was also found that stretching the film did not lower the thermal conductivity of the same region.

Study of plastic flow on intermetallic compounds formation in friction welding of aluminum alloy to stainless steel

During friction welding of Al alloy to steel, the metallurgical reaction of Al and Fe can be occurred under the coupling effect of heat and rotational plastic flow. However, the detailed role of them in contributing intermetallic compounds (IMCs) development remains largely unknown, causing the significant impediment in further tailoring IMCs. In this regard, a thermal compression bonding process was elaborately designed to highlight the influence of frictional flow on the formation of IMCs in friction welding. From the results, it was revealed in friction welding process, frictional flow significantly promoted the formation of sub-micron sized IMCs along weld interface, since in thermal compression bonded specimens, a significantly thinner IMCs were confirmed. Due to the non-uniform distribution of heat and plastic flow rate at different regions along interface, an inhomogeneous distribution of IMCs in terms of thickness was also identified in friction welded joint. Additionally, the frictional flow and stirring effect of Al alloy also resulted in the convex on friction surface at steel side stripped into Al alloy, enhancing the appearance of IMCs particles. Therefore, frictional plastic flow was supposed to predominately contribute to the growth of IMCs in friction welding of Al alloy to steel.

Sequence-Defined Nanotubes Assembled from IR780-Conjugated Peptoids for Chemophototherapy of Malignant Glioma.

Near-infrared (NIR) laser-induced phototherapy through NIR agents has demonstrated the great potential for cancer therapy. However, insufficient tumor killing due to the nonuniform heat or cytotoxic singlet oxygen (1O2) distribution over tumors from phototherapy results in tumor recurrence and inferior outcomes. To achieve high tumor killing efficacy, one of the solutions is to employ the combinational treatment of phototherapy with other modalities, especially with chemotherapeutic agents. In this paper, a simple and effective multimodal therapeutic system was designed via combining chemotherapy, photothermal therapy (PTT), and photodynamic therapy (PDT) to achieve the polytherapy of malignant glioma which is one of the most aggressive tumors in the brain. IR-780 (IR780) dye-labeled tube-forming peptoids (PepIR) were synthesized and self-assembled into crystalline nanotubes (PepIR nanotubes). These PepIR nanotubes showed an excellent efficacy for PDT/PTT because the IR780 photosensitizers were effectively packed and separated from each other within crystalline nanotubes by tuning IR780 density; thus, a self-quenching of these IR780 molecules was significantly reduced. Moreover, the efficient DOX loading achieved due to the nanotube large surface area contributed to an efficient and synergistic chemotherapy against glioma cells. Given the unique properties of peptoids and peptoid nanotubes, we believe that the developed multimodal DOX-loaded PepIR nanotubes in this work offer great promises for future glioma therapy in clinic.

Fabrication of Polyethersulfone/Functionalized MWCNTs Nanocomposite and Investigation its Efficiency as an Adsorbent of Pb(II) Ions

The novel polyethersulfone/ethylenediamine-functionalized multiwall carbon nanotubes (PES/MWCNTs-NH2) nanocomposite was synthesized and introduced as an efficient adsorbent for Pb(II) removal from aqueous solutions. The characterization analyses, including FTIR, TGA, SEM, and EDX, confirmed the successful functionalization of MWCNTs through three steps acidic treatment, acylation with SOCL2, and amine functionalization. The influence of MWCNTs functionalization, pH, stirring speed, contact time, and adsorbent dosage on the Pb(II) adsorption by PES/MWCNTs-NH2 nanocomposite was investigated. The optimum condition was obtained on neutral pH, contact time 10 min, stirring speed 400 rpm, and adsorbent dosage 0.1 g of PES/1% MWCNTs-NH2, which reached the maximum adsorption capacity of 272 mg/g. The equilibrium studies were investigated by consideration of Langmuir, Freundlich, Temkin, and D-R isotherm models, which revealed that Pb(II) adsorption onto PES/MWCNTs-NH2 was performed on a heterogeneous surface with a non-uniform distribution of heat of adsorption. Also, it confirmed that the chemisorption process was favorable. The kinetic studies through pseudo-first-order, pseudo-second-order (as a reaction-based model), and Boyd models (diffusion-based model) showed that the chemisorption adsorption rate was fast, and controlled by film diffusion. Thermodynamic studies indicated that Pb(II) adsorption process onto PES/MWCNTs-NH2 was spontaneous, endothermic, by increasing the randomness of the solid/liquid interface.

Effect of different tool pin diameter on mechanical properties of friction stirred welded AISI 304 stainless steel plate

The investigations was carried out to investigate the effect of different friction stir tool pin diameter on mechanical, microstructural properties and welding efficiency of the Stainless Steel AISI 304 friction stir welded specimen. The experiment were carried out at constant tool rotating speed of 1050 rpm, welding speed of 24 mm/min and tools with diameter ranging from 2.5 mm to 4.9 mm at 0.3 mm increasing value. The constant axial force of 10 KN has been applied to perform the friction stir joining. The welded specimens were inspected microscopically and analyzed to obtained mechanical properties such as hardness and UTS, as per the ASTM standard. The maximum tensile strength has been observed as 504 MPa at 2.8 mm tool pin diameter. The maximum welding efficiency of 99% has been observed. The lower tensile strength of the other joints found were due to lower and non-uniform heat distribution at the surface. The microstructure of welded specimen has been analyzed and characterized at different zones by using an optical microscope.