Interface Temperature Research Articles

Experimental and molecular simulation study of a novel benzimidazole-linked polymer membrane for efficient H2/CO2 separation

Developing novel materials for membrane separation is extremely crucial. Benzimidazole-linked polymers (BILPs) show great potential for H2 purification due to their high thermal and chemical stability, while only a few BILPs have been used for membrane-based gas separation. In this work, the BILP-5 composite membranes were prepared via a facile interfacial polymerization. Dense and smooth BILP-5 composite membranes were prepared on α-Al2O3 support and characterized by scanning electron microscope (SEM) and atomic force microscope (AFM). The effects of interfacial polymerization reaction duration, temperature, and pressure on the gas separation performance of BILP-5 membranes were systematically investigated. The resultant BILP-5 membrane shows good stability and a high H2/CO2 selectivity of 16 with a H2 permeance of 362 GPU under mixed gas test at room temperature, which exceeds the 2008 upper bound. Furthermore, the H2/CO2 separation mechanism of BILP-5 membranes was investigated through molecular dynamics simulations. Coupled with the merits of simple preparation, good stability, and excellent gas separation performance, BILP-5 is expected to be one of the most promising membrane materials for H2/CO2 separation.

Simulation of Temperature Distribution in a Brake Pad Ceramic Composite Material

The temperature distribution is an important aspect of any brake pad composite material. The braking temperature affects the performance and efficiency of any brake pad composite material. It is difficult to measure the interface temperature between the brake pad and disc by thermocouples or infrared thermal sensors during braking. This work investigates the temperature distribution of a ceramic composite brake pad material by the transient thermal analysis method. The transient thermal approach method helps to visualize the interface temperature through simulation. Also, it provides pin temperature at a distance of 4 mm and 6 mm away from the disc surface to observe the temperature distribution of the brake pad. The experimental values of the temperature of the pin at 4 mm and 6 mm away from the disc are collected from the literature and compared with the predicted temperature through simulation. It is found that there is a close agreement between the predicted and experimental temperature values.

A green modification technology of carbon nanotubes toward enhancing the tribological properties of aqueous-based lubricants

Herein, a green and efficient method is proposed for preparing highly stable aqueous dispersions to realize the potential applications of carbon nanotubes in water. Functionalized carbon nanotubes (CNTs@CMC-Na) were rapidly prepared using a microwave-assisted ball milling apparatus. Sodium carboxymethyl cellulose was grafted on carbon nanotubes through various actions and CNTs@CMC-Na exhibited excellent dispersibility, which increased the thermal conductivity of pure water by 97.6 %. The tribological tests and surface analysis indicate that CNTs@CMC-Na have protective, mending, and cooling effects at the friction interface. The CNTs@CMC-Na aqueous dispersion (0.2 wt%) reduced the average friction coefficient, average wear width, and temperature of the friction interface by 50.13 %, 58.3 %, and 38.9 %, respectively. This study provides a new idea for the preparation of lubricant additives.

Mechanism of bonding during laser transmission welding using EIP absorber

ABSTRACT This paper aims to investigate the bonding mechanism during laser transmission welding of polycarbonate sheets using an electrolytic iron powder (EIP) absorber. The experiments are performed at different scan speeds and laser powers. The mechanical strength is determined by the lap shear test. The influence of line energy, interface temperature, and absorptivity on weld strength is discussed. The weld characteristics, bond morphology, and elemental distribution at the cross-section and fracture interface of the welded samples are analyzed. The results show that the maximum breaking strength of 1180 N is obtained at the 400 mm/min scan speed and 100 W laser power. The iron particles are observed mechanically interlocked at the lowest line energy with partial chemical bonding. However, the chain diffusion and chemical bonding have been increased with line energy. Thermal degradation and burning of the polycarbonate at the interface restrict the bonding and reduces the weld strength.

Vapor mixing in turbulent vaporizing flows

Scalar mixing and evaporation processes are analyzed in a compressible two-phase homogeneous and isotropic turbulence configuration. To this end, the fully compressible Navier–Stokes equations are solved using a pressure-based method and a mass-conservative interface capturing method (CLSVOF). Temperature and vapor mass fraction transport equations are coupled with the momentum equation via the evaporation rate: i.e. heat and mass transfer has an effect on the flow dynamic through the generation of a Stefan flow at the interface. In this formalism, a pressure equation is developed to include the acoustic, thermal dilatation and compressibility effects. Moreover, the method can consider several gas structures in the same domain, each with independent temperature, density, and thermodynamic pressure. The latter is important to simulate atomization, where interaction among the liquid structures (such as breakup or coalescence) can generate multiple gas inclusions. This work is one of the first to describe with high fidelity the vaporization and turbulent mixing occurring in dense two-phase flows.A statistical analysis of the vapor mass fraction field is performed. The obtained results reveal the influence of the non-homogeneous scalar source at the interface, which depend directly on the local interface temperature, on the PDF shape. Under these conditions, the vapor mass fraction PDF deviates from the Gaussian and beta PDF shapes, frequently used for turbulent combustion modeling. Furthermore, access to the local surface averaged vapor mass fraction and evaporation rate at the interface allows a statistical analysis of these variables. Results show a large dispersion of both quantities, especially at the early times of the simulations, which contradict the usual assumption of a constant vapor mass fraction (or vaporization rate) at the interface used in the literature in standard vaporization models. Finally, the influence of the mean interface curvature on the evaporation rate is quantified and discussed. Large evaporation rate are present when the interface is convex (positive mean curvature). On the contrary, local saturation zones are present near concave interface (negative mean curvature), reducing the evaporation rate magnitude.

Comparative study of the current-carrying tribological properties of carbon graphite composites with different hardnesses

To investigate the effect of sliding speed and electrical current on the current-carrying friction performance of carbon brushes with different hardnesses. In this paper, two carbon-graphite material samples with different hardnesses manufactured by a powder metallurgical process were prepared. And a pin-disc current-carrying friction tester was used for testing. The results showed that the difference in hardness has a noticeably different effect on the sliding contact resistance and interface temperature rise of the material. As the electric current changes, the material with low hardness exhibited good adaptability. Then, the adhesive wear occurred for all materials of different hardnesses, and it changed to abrasive wear mainly with increasing electrical current. As the sliding speed increased, the wear rate of low-hardness material dropped, while the opposite trend was observed for high-hardness material. The increased sliding speed does not generate remarkable damage to the contact surface of the high-hardness material, which demonstrated good resistance to mechanical shocks.

Green Surfactant Made from Cashew Phenol for Enhanced Oil Recovery.

Surfactants play an important role in enhancing oil recovery (EOR). With the development of tertiary oil recovery technology and the continuous improvement of environmental protection requirements, green environmentally friendly surfactants play an important role in replacing conventional surfactants. In this paper, cardanol polyoxyethylene ether (CPE) was synthesized from natural biomass cardanol. Its structure was characterized, and its surface/interface properties, salt and temperature resistance, wettability, emulsification, and oil displacement effect were studied experimentally. The results showed that CPE had good interfacial activity and temperature and salt tolerance, which can reduce the oil-water interfacial tension to 10-1 mN/m. The emulsion formed by CPE had good stability. With the increase in CPE dosage, the droplet size of the emulsion decreases. The emulsion stabilized by CPE can effectively enhance oil recovery by 11.8%. Therefore, CPE not only is environmentally friendly but also has great application potential in the field of EOR.

Influence of thermocapillary flow induced by a heated substrate on atomization driven by surface acoustic waves

Thermocapillary flow on the mechanism of interfacial destabilization prior to atomization of a sessile Newtonian droplet subjected to surface acoustic waves (SAWs) is analyzed. We assumed that an interfacial temperature distribution is induced on the free surface of the millimeter-sized water droplet since the droplet is on a heated substrate. Given the dependence of surface tension on interfacial temperature, shear stresses combined with SAWs lead to the development of thermocapillary flow. The evolution equation for a small-scale droplet under the combined influence of SAW atomization and thermocapillary flow is derived via an asymptotic approach to the hydrodynamic equations, arising the acoustic capillary and Marangoni numbers. In this limit, our simplified droplet model can predict capillary instability leading to atomization once a critical amplitude is reached for the induced capillary waves at the liquid droplet. In doing so, our model also represents the influence of the thermocapillary effect on the interfacial deformation of the droplet and shows how the Marangoni flow promoted by a heated substrate counteracts the acoustic stress, leading to a virtually uniform droplet aspect ratio and thus larger aerosol diameters compared to the isothermal case. These results are supported by the development of a novel analytical expression that has allowed us to estimate the characteristic aerosol size under thermocapillary flow and SAW excitation, and to postulate thermocapillary flow as a new valuable means of explaining the regulation of the characteristic aerosol size at SAW atomization.

MODEL DEVELOPMENT AND PERFORMANCE IMPROVEMENT OF A PHOTOVOLTAIC-THERMOELECTRIC SYSTEM BY INTEGRATING AND OPTIMIZING PHASE CHANGE MATERIALS

Integrating phase change materials (PCMs) with concentrated photovoltaic-thermoelectric (PV-TE) systems can effectively control the interface temperature between PV and TE components and improve the full solar-spectrum utilization efficiency. However, since the structure of photovoltaic-phase change material-thermoelectric (PV-PCM-TE) systems is complex and the temperatures among the components are coupled and affect each other, the photo-thermal-electric conversion characteristics under the actual physical properties need to be analyzed by a more detailed model, and the suitable operating conditions for PV-PCM-TE systems remain clear. There is still a lack of the method for improving the system performance. Therefore, a three-dimensional transient model is established herein by combining the Monte Carlo ray-tracing method and finite volume method to simulate the complex energy conversion processes of the PV-PCM-TE system. Based on this, performances of PV-PCM-TE, PV-TE, and PV systems are compared under different operating conditions, and the applicable conditions for PV-PCM-TE systems are analyzed. Then effects of key parameters of the phase change module are investigated. In the end, to further improve the system performance, a partition screening method of PCM is proposed considering the nonuniform solar radiation on photovoltaic surfaces, and the selection and layout area of PCMs are optimized. The results present that the applicable operating conditions are low concentration ratio (< 20) and low heat transfer coefficient (< 20 W·m<sup>-2</sup>·K<sup>-1</sup>). In terms of structural parameters, the system power generation is most significantly affected by the width. In terms of PCM physical properties, it is most affected by the PCM density, followed by latent heat. For different concentration ratios, there are different optimal melting points to achieve the highest power generation. The proposed PCM partition screening method can efficaciously control PV-TE interface temperature, and reduce photovoltaic cells' temperature by 47°C. The system efficiency can be increased by 4.8% and 4.2% after the optimization compared with that of the single PV cell and the traditional PV-TE system, respectively.

Molecular Dynamics Simulation of Interface Properties between Water-Based Inorganic Zinc Silicate Coating Modified by Organosilicone and Iron Substrate

The interface properties of Fe(101)/zinc silicate modified by organo-siloxane (KH-570) was studied by using the method of molecular dynamics simulation. By calculating the temperature and energy fluctuation of equilibrium state, equilibrium concentration distribution, MSD of layer and different groups, and interaction energy of two interface models, the influencing mechanism on the interface properties of adding organosiloxane into coating system was studied at the atomic scale. It shows that the temperature and energy of interface oscillated in a small range and it was exited in a state of dynamic equilibrium within the initial simulation stage (t < 20 ps). It can be seen from the multiple peak states of concentration distribution that the iron substrate, organo-siloxane and zinc silicate are distributed in the form of a concentration gradient in the real environment. The rapid diffusion of free zinc powder in zinc silicate coating was the essential reason that affected the comprehensive properties of coating. The interface thickness decreased from 7.45 to 6.82 Å, the MSD of free zinc powder was effectively reduced, and the interfacial energy was increased from 104.667 to 347.158 kcal/mol after being modified by organo-siloxane.

Temperature Dependence of the Static Friction Coefficient of Common Recyclable Polymers

According to the classical adhesion explanation for the phenomenon of friction, the friction coefficient between two surfaces is defined as the ratio between the horizontal friction force exerted on each surface and the perpendicular normal force between each surface. There is a paucity of published investigations into the relationship between the contact temperature of a polymer-nonpolymer physical interface and the resultant static friction coefficient at varying temperatures. This study investigates the relationship between temperature and the static friction coefficients of five recyclable thermoplastic polymers in polymer-aluminum interfaces across a range of temperatures. The results demonstrate a generalizable relationship between the static friction coefficient and the contact temperature of polymer-aluminum interfaces which corresponds to polymer-specific phase-change temperatures.

Thermal Field Simulation and Analysis of Tulip Contact Based on Virtual Material Method

In order to analyze the temperature distribution of circuit breaker tulip contact, a thermal field simulation model for tulip contact is built combined with the electromagnetic-stress-thermal coupled finite element simulation and virtual material method which models the contact resistance characteristics of tulip contact. The temperature rise characteristic of tulip contacts under rated current conditions and short-circuit conditions is analyzed with the model. Results show that the virtual material method can describe the contraction resistance and additional resistance at the end of the contact finger simultaneously, so as to simulate the partial high temperature of the contact interface. Then, the influence of spring pressure and pressure uniformity on the thermal field of tulip contact is analyzed. Results show that the decrease of spring pressure and the imbalance of contact finger pressure may lead to an increase in the temperature rise of the tulip contact. The proposed method can be used as a reference for the design and the overheating analysis of tulip contact.

Experimental research on the thermal characteristic of low-voltage alternating current (AC) arc faults

The objective of this paper is to study the thermal characteristic of low-voltage alternating current (AC) arc faults. Two series of experiments were designed, including polyvinyl chloride (PVC) wire ignitions experiments and electrode arcing experiments (non-ignitions) subjected to arc faults at different effective currents. The ignition time of the wire and the temperature of the electrode were investigated to characterize the arcing hazard. Results show that the ignition time of the wire decreases with the increasing arc current, and the wire with a larger cross-section area requires more time to be ignited at the same current. For non-ignition experiments, the electrode temperature increases first and then varies little. A heat equilibrium stage can be reached, where the heat transfer of the arc to the electrode is equal to the heat dissipation of the electrode. Furthermore, a heat transfer model for the arc fault is established to obtain the electrode temperature. The temperature of the arc-electrode interface is used to characterize the arc energy, and it is found the temperature showed a logarithmic increase with the current. The results of this study may be useful in the safety design of electrical wires, and can be exploited as hazard indicators for the risk assessment of electrical fires.

Experimental and numerical study on an innovative protective measure for high strength concrete using the bilayer method

Fire-induced spalling is an ongoing primary concern in the application of high-strength concrete in building structures. A reliable and practical protective method is thus highly desirable and critical for the prevention of fire-induced spalling. Therefore, an innovative bilayer method, in which high strength concrete is surrounded by a layer of normal strength concrete of sufficient thickness, is proposed. A total of 20 columns are cast to investigate the feasibility of the bilayer design, of which 15 are put to fire testing and the other five to ambient compression testing. The effects of protective layer thickness, duration of exposure to fire, sealed condition and reinforcement confinement are investigated. Experimental results indicate that the performance of bilayer columns is similar to that of high strength concrete columns with regard to strength and deformation. Fire-induced spalling occurs within the first 30 min of heating at an interface temperature of around 150 °C. Lastly, a minimum effective thickness of 100 mm is recommended to prevent spalling.

Computational investigation of vertical upflow boiling of liquid nitrogen and effects of bubble collision dispersion force

The present study investigates the performance of 2-D axisymmetric computational fluid dynamics (CFD) in predicting boiling characteristics of liquid nitrogen flowing vertically upwards along a uniformly heated circular tube. Investigation of the popular Volume of Fluid (VOF) model reveals (a) inaccurate surface tension calculation which degrades interface tracking, and (b) under-representation of bubble-to-bubble interaction, which stems from the innate nature of employing a single momentum equation in VOF. To alleviate VOF shortcomings, Coupled Level Set VOF (CLSVOF) is adopted in ANSYS FLUENT, including a user defined function to account for the crucial effects of bubble collision dispersion force. The CFD simulation results are validated against wall temperature and volume fraction results from prior benchmark experiments corresponding to four different wall heat flux conditions at nearly identical mass velocities. Predictions are also provided for axial variations of interfacial flow pattern, fluid temperature, and fluid velocity, flow characteristics that are very difficult to measure in cryogenic experiments. The CFD simulation results are shown to be highly accurate at predicting the nucleate boiling portion of the flow boiling curve.

Ultrasonic Welding of Aluminum to Steel: A Review

As a solid-state bonding technology, ultrasonic welding (USW) has the characteristics of green energy saving and environmental friendliness. It is more suitable for joining dissimilar metals than other welding technologies. The aluminum-to-steel USWed joint has been widely used in the automotive and aviation industries. Currently, there is no review literature report on aluminum-to-steel USW. The main physical phenomena of the USW process include interface temperature increase, ultrasonic softening, plastic deformation, formation and growth of the IMCs, and dynamic recrystallization. Hence, the microstructures and mechanical properties of aluminum-alloy-to-low-carbon-steel, aluminum-alloy-to-stainless steel, and aluminum-alloy-to-galvanized-steel-joints by USW are reviewed. Moreover, the effect of interface temperature, interface plastic deformation, and interface macrostructure and microstructure is explored. Lastly, tensile-shear and fatigue strength of joints and numerical simulation of the USW process are also discussed. In addition, some new application types of aluminum-to-steel USW are introduced. Finally, the future trends of aluminum-to-steel USW with guidance are provided.

Effect of Alcohol on the Mechanical and Electrical Properties of Ultrasonic Spot Welded Cu/Cu Joints

In order to improve the Cu/Cu joint quality, the bottom Cu sheet surface to be welded was dampened by a drop of absolute ethyl alcohol before the welding. Then, the ultrasonic spot welding (USW) was utilized to join a 0.5 mm thick Cu sheet to a 1.0 mm thick Cu sheet. The results demonstrated that, due to the action of the alcohol, obvious changes of the welding interface temperature, effective thickness, bond density, interface microstructure, joint resistance, micro-hardness, lap shear strength and fracture mode occurred in comparison with the joint without alcohol. Discontinuous dynamic recrystallization took place at the welding interface and facilitated the migration of grain boundaries across the contact interface, leading to the formation of the metallurgical bonding between the two Cu sheets.

Machinability investigation of Chromoly steel using TiN/Al2O3/TiCN/TiOCN multilayer coated tungsten carbide tool inserts with artificial neural network methodology

AbstractEnhancing the machining efficiency of hardened steel using four‐layer coated tungsten carbide tools has gained a lot of interest among manufacturing engineers. This paper reports the machining performance of AISI 4140 steel using TiN/Al2O3/TiCN/TiOCN multilayer coated tungsten carbide tool inserts. The impact of cutting speed, depth of cut, and the nose radius on machining force, tool chip interface temperature, surface roughness, and chip forms was ascertained using full factorial machining experiments and artificial neural network (ANN) methodology. The machining force evaluated using Logistic Sigmoid activation function resulted in the highest root mean square error (RMSE) of 4.076 and regression value of 0.998. The maximum error between the ANN predicted results and experimental results for machining force, cutting temperature and surface roughness was about 2.4%, 5.3%, and 2.07%, respectively. The best architecture for ANN was “3‐6‐4” which had a coefficient of regression value of 0.97. However, in case of chip form, some of the ANN predicted values could not be mapped to ISO standard chip form and hence prediction accuracy of 80% was achieved.

Suppression and Revival of Superconducting Phase Coherence in Monolayer FeSe/SrTiO3.

Monolayer FeSe grown on SrTiO3 (FeSe/STO) is an interfacial high-temperature superconductor distinctively different from bulk FeSe. However, the superconducting phase coherence of the interface is challenging to probe due to its fragility in the atmosphere. Here, we perform in situ mutual inductance under ultrahigh vacuum on FeSe/STO in combination with band mapping by angle-resolved photoemission spectroscopy. We find that even though the monolayer shows a gap-closing temperature above 50 K, no diamagnetism is visible down to 5 K. This is the case for few-layer FeSe/STO until it exceeds a critical number of five layers, where diamagnetism suddenly appears. The suppression of diamagnetism in the monolayer is also lifted by depositing a top FeTe layer. However, Tc and superfluid density both decrease with thicker FeTe, suggesting unconventional electron pairing and phase coherence competition. Our observation may be understood by a scenario in which the interfacial superconducting phase coherence is highly anisotropic.

Recycling of Bottle Grade PET: Influence of HDPE Contamination on the Microstructure and Mechanical Performance of 3D Printed Parts.

As part of a project that aims to provide people with disabilities with simple assistive devices in Colombia, the possibility of creating a PET filament that can be printed by Fused Deposition Modelling (FDM) from beverage bottle waste was investigated, with the aim to remain as simple as possible in terms of plastic collection, sorting, processing, and printing. Recycled PET filaments were thus produced by extrusion from collected PET bottles, with the potential addition of HDPE, which comes from caps and rings. The microstructure, mechanical performance, and printing quality of parts produced with these filaments were investigated in comparison to commercial PET virgin and recycled filaments. HDPE presence as an immiscible blend did not affect the ease of extrusion or the quality of the printing, which were all satisfactory. In some conditions, the addition of 5 wt% of HDPE to recycled PET had a toughening effect on otherwise brittle samples. This behavior was attributed to the presence of elongated HDPE inclusions resulting from shear forces induced by the layer-by-layer printing, provided that the interface temperature remained high between layer depositions. This confirms that the mechanical performance of recycled PET is very sensitive to the processing conditions, especially in the case of 3D printing. Nonetheless, this low-cost process that did not require sophisticated compatibilization schemes allowed for the printing of parts with mechanical properties comparable to those obtained with high purity, commercially recycled filaments, opening interesting perspectives for a low-cost PET recycling process.