Joule Effect Research Articles

Medium-Frequency Electrical Resistance Sintering of Soft Magnetic Powder Metallurgy Iron Parts

The fabrication of soft magnetic Fe parts by the medium-frequency electrical resistance sintering (MF-ERS) technique is studied in this paper. This consolidation technique involves the simultaneous application to metallic powders of pressure and heat, the latter coming from the Joule effect of a low-voltage and high-intensity electric current. Commercially pure iron powder was used in the consolidation experiences. The porosity distribution, microhardness, electrical resistivity and hysteresis curves of the final compacts were determined and analysed. The results obtained were compared both with those of compacts consolidated by the conventional powder metallurgy (PM) route of cold pressing and vacuum furnace sintering, and with fully dense compacts obtained by double cycle of cold pressing and furnace sintering in hydrogen atmosphere.

A Review of Multiple Scale Fibrous and Composite Systems for Heating Applications.

Different types of heating systems have been developed lately, representing a growing interest in both the academic and industrial sectors. Based on the Joule effect, fibrous structures can produce heat once an electrical current is passed, whereby different approaches have been followed. For that purpose, materials with electrical and thermal conductivity have been explored, such as carbon-based nanomaterials, metallic nanostructures, intrinsically conducting polymers, fibers or hybrids. We review the usage of these emerging nanomaterials at the nanoscale and processed up to the macroscale to create heaters. In addition to fibrous systems, the creation of composite systems for electrical and thermal conductivity enhancement has also been highly studied. Different techniques can be used to create thin film heaters or heating textiles, as opposed to the conventional textile technologies. The combination of nanoscale and microscale materials gives the best heating performances, and some applications have already been proven, even though some effort is still needed to reach the industry level.

Renewable and Electroactive Biomass-Derived Tubes for CO2 Capture in Agroindustrial Processes

Tube-shaped renewable carbon materials were developed to work as separation agents for CO2 capture in agroindustrial and intensive farming facilities. The tubes have electrical properties and moderate CO2 adsorption capacities. These materials can be heated directly through the Joule effect by applying an electric potential between the ends and thus reaching temperatures higher than 473 K in a few seconds with an applied voltage of near 10 V. The tube’s temperature can be easily controlled by manipulating the applied voltage, which is of interest for the development and design of CO2 capture processes through electric swing adsorption. The tubular form of the material also provides the alternative to be filled up with adsorbents like zeolite and metal–organic frameworks to produce highly selective structured adsorbents based on renewable carbon materials with the advantage of providing direct Joule heating. These materials were studied as separation agents to be part of cycles like vacuum swing adsorption, electric swing adsorption, and both combined. The tubes were tested through consecutive and repeated adsorption and Joule heating desorption experiments. The dynamics of the tube’s temperature and the CO2 gas-phase composition showed consistency and repeatability. The results revealed the robustness and reliability of the biomass-derived tubes to work as separation agents for CO2 capture.

Ultrafast high-temperature sintering (UHS) of fine grained α-Al2O3

Ultrafast High-temperature Sintering (UHS) allows consolidation of ceramics in just a few tens of seconds. The green body is placed within a carbon felt heated by the Joule effect at temperatures up to 3000 °C. Here, we propose a combined experimental and numerical analysis to enable the fabrication of fully dense and fine-grain α-Al2O3 samples using a multistep computer-controlled current profile. Reference samples processed using a single step current formed cracks at the onset of shrinkage due to their uneven temperature distribution. Fully coupled simulations accounting for electric current, voltage, power, temperature and shrinkage allowed us to improve the experimental setup and to define the current profiles required to UHS highly dense (i.e., relative density > 99 %) 3 mm thick samples with an average grain size of 0.77 μm.

Transient Cooling and Heating Effects in Holey Silicon-Based Lateral Thermoelectric Devices for Hot Spot Thermal Management

Lateral thermoelectric devices, where the Peltier cooling and heating occur in a lateral direction, have shown promise for thermal management of on-chip hot spots, and because of the device orientation, thermoelectric materials with anisotropic properties such as holey silicon have shown even more promising cooling potential. However, the role of anisotropy in transient cooling and heating effects is little known, and thermal management optimization using a pulse has not been considered with anisotropic materials. Here, we study temporal and spatial interplays of Peltier, Joule, and Thomson effects in a holey silicon-based lateral thermoelectric device with varying pulse conditions and material properties. Our simulations show a supercooling effect, driven by Peltier cooling before Joule heating diffuses in, and that holey silicon with anisotropic thermal conductivities is favorable by delaying the diffusion in the lateral direction while allowing rapid heat dissipation in the vertical direction. Depending on the local temperature distribution, the Thomson effect is shown to strengthen the supercooling effect. A holey silicon-based thermoelectric device with a 1 kW · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> hot spot shows temperature reductions from 117 °C to 102 °C in steady-state and temporarily to 100 °C with optimal pulse conditions. The transient cooling performance can be further improved by incorporating phase-change materials within holey silicon, in which their melting process delays a temperature overshoot. The anisotropy, specific heat, and latent heat play important roles in determining the transient cooling performance. Our findings show that lateral thermoelectric devices with anisotropic properties are promising for dynamic thermal management of on-chip hot spots.

Multifunctional and superhydrophobic cellulose composite paper for electromagnetic shielding, hydraulic triboelectric nanogenerator and Joule heating applications

• Multifunctional and superhydrophobic cellulose composite paper (CCP) is fabricated. • CCP shows a high EMI shielding effectiveness and electrical conductivity. • The superhydrophobic surface is used as the hydraulic triboelectric nanogenerator. • Surface temperature of CCP can reach 140 °C with a applied voltage of 6 V. Cellulose-based materials have attracted tremendous interest recently due to their fascinating merits of renewability, biodegradability, and low cost, holding great promise in electromagnetic protection, clean energy harvesting, and thermal management. However, the simple and effective integration of multiple functions into single cellulose material remains a challenge. Herein, we report the fabrication of a multifunctional and superhydrophobic cellulose composite paper (CCP) via coated MXene modified by in-situ polymerized polypyrrole and PDMS/candle soot on the opposite surface of the paper. CCP exhibits high-performance electromagnetic interference shielding effectiveness (~40 dB) while maintaining high electrical conductivity (1467 S/m). Moreover, the superhydrophobic surface of CCP can be used as the hydraulic triboelectric nanogenerator (H-TENG) to harvest water energy due to the liquid–solid contact triboelectrification and electrostatic induction. The hydraulic triboelectric energy can be captured and released when water droplets drop from a height of 2 cm and roll at a tilt angle of 20°, the output current can reach a peak of 0.8 nA. Furthermore, the surface saturation temperature of CCP can reach 140 °C with a low applied voltage of 6 V enabled by the Joule effect. Thus, CCP holds great potentials in applications of integrated smart electronics, clean energy harvesting, and thermal management.

Effect of electric field-induced alignment of conductive fillers in polyurethane

Effect of an electric field (Joule heating) on the electrical conductivity of four different systems of polyurethane filled with multiwall carbon nanotube, graphite, Cu particulates, and Cu flakes ranging from 10 to 80 wt%. The effect of filler shape on percolation threshold and maximum conductivity was also discussed. In the Joule effect test, the amount of adhesive resistance and surface temperature of the samples were instantaneously measured. It was observed that all four systems showed a negative temperature coefficient (NTC) behavior upon applying an electric field. Characterization was performed via scanning/transmission electron microscopy, Raman/infrared spectroscopy, and four-probe electrical conductivity measurements. By mathematical modeling, the possibility of rotation of fillers was investigated, based on which mechanisms are proposed for the observed NTC behavior.

Temperature-dependent electrical resistivity of macroscopic graphene nanoplatelet strips

This paper studies the temperature dependence of the electrical resistivity of low-cost commercial graphene-based strips, made from a mixture of epoxy and graphene nanoplatelets. An equivalent homogenous resistivity model is derived from the joint use of experimental data and simulation results obtained by means of a full three-dimensional (3D) numerical electrothermal model. Three different types of macroscopic strips (with surface dimensions of cm2) are analyzed, differing in their percentage of graphene nanoplatelets. The experimental results show a linear trend of resistivity in a wide temperature range (−60°C to +60°C), and a negative temperature coefficient . The derived analytical model of temperature-dependent resistivity follows the simple law commonly adopted for conventional conducting materials, such us copper. The model is then validated by using the graphene strips as heating elements by exploiting the Joule effect. These results suggest that such materials can be used as thermistors in sensing or heating applications.

Capacitor Electrical Discharge Consolidation of Metallic Powders—A Review

Manufacturing metallic materials from elemental or alloyed powders is an option in many industrial processes. Nevertheless, the traditional powder metallurgy processing including furnace sintering is at times detrimental for the microstructure attained in the powders. Alternative sintering processes based on the use of electricity and the energy obtained by the Joule effect in powder particles can be quick enough to avoid microstructural changes. In particular, when the energy is stored in a capacitor and then discharged, the heating process is extremely quick, lasting milliseconds or even microseconds. This process, generally known as electrical discharge consolidation, has been applied to a wide variety of metallic materials, easily preserving the original microstructure of the powders. Both porous or homogeneous and highly densified material can be obtained, and without losing the desired properties of the consolidated material. A general overview of the process and applications, as well as the results obtained by different research groups around the world, have been reviewed in this manuscript.

Applied methodology for temperature numerical evaluation on high current leads in power transformers

The majority of power transformer manufactures use their own proprietary design to build oil-immersed power transformers with high current busbar leads (HCBL) because there is no standardization or registered standard in the technical literature. Anyway, specialists certainly require a highly accurate temperature estimation regardless of the proprietary designs used to build these power transformers. It is well known that the temperature at the copper HCBL surface is mainly influenced by the Joule effect induced by the passing current, paper wrapping insulation characteristics, and temperature of the surrounding oil. In this context, we suggest a novel non-invasive technique for estimating the temperature of HCBL power transformers. Such methodology is simple and can be used to estimate the temperature for any power transformer despite designs strategies, becoming an algorithm that can be used in several commercial programs. The temperature is taken as a function of variables and measurements easily acquired from the transformer and, therefore, turns out to be an original and simple method. The methodology is based on the evaluation of the convection heat transfer coefficient h, which depends on the geometry factors and cooling fluid characteristics of the transformer. Since temperature levels are critically sensitive to h variations, Computer Fluid Dynamics (CFD)-based commercial software are a common-place tool for thermal analysis of power transformers as coefficient h must be calculated with very high precision and correctly evaluated. However, this solution have both high financial and computational burden. The skin and proximity effects are taken into account in the proposed methodology by using the Finite Element Method – FEM. Thus, we propose an efficient and simplified solution for temperature estimation. We will show that the solution is as accurate as the CFD programs, albeit, more economically and computationally viable. We validate the results by means of measurements made with Fiber Optic Temperature Sensors during a full-load test and show the estimation numerical accuracy for parameter h.

Liquid metal MHD flow influence on heat transfer phenomena in fusion reactor blankets

DEMO reactor is projected as a technological demonstrator and a component test reactor for several key systems such as the breeding blanket. The dual coolant lithium lead (DCLL) is one promising breeding blanket candidate that performs the functions of shielding, part of the cooling and breeding with the same liquid metal fluid. PbLi is also in charge of transporting the bred tritium to the Tritium Extraction System. Structural cooling of the blanket walls is performed by pressurized helium flow which also transfers heat to the balance of plant. Keeping a proper distribution of thermal loads between the two coolants is a key aspect to reach a plant high efficiency. The thermal power transferred from the liquid metal to the helium channels depends on the flow regime. While liquid metal flows under the magnetic field, the magnetohydrodynamic (MHD) phenomena will occur, influencing the flow regime and the velocity profile. The heat is volumetrically deposited in the liquid metal coolant due to the interaction between the highly energetic neutrons originated in the plasma and the coolant. The heat deposition profile is roughly exponential causing temperature differences across the same channel cross section. Temperature gradients induce buoyant effects altering the expected MHD profile and affecting the heat transfer rate from the liquid metal to the surrounding walls cooled with helium. It is of utmost interest to identify the effects of the main flow parameters on the heat transfer coefficient under such complex conditions. The work studies computationally a domain consisting of a liquid region and a surrounding solid region electrically and thermally coupled using latest EU DCLL design characteristics. A fully developed flow is assumed where buoyancy is modelled under the Boussinesq approximation. Joule effect has been considered negligible compared to the neutron deposition. The influence of the buoyant MHD phenomena to the heat transfer coefficient is analysed parametrically with a CFD solver implemented in OpenFOAM®. The parameters investigated here are the Reynolds, Hartmann and Grashof numbers, the Grashof ratio, and the wall conductance ratio (cw).

Micro texture of titanium alloys excited nonlinearly by electromagnetic pulse

The influence of electromagnetic pulse (EMP) on properties of alloys has been widely known. However, it is still vague for the influence mechanism of EMP on alloy microstructure and one of the biggest debates is whether athermal effect plays a role or not. A special experiment has been designed to explore this problem in this paper. As observed experimentally, micro texture on titanium alloy surface distorts dramatically and collapse occurs at micro zone under the effect of EMP with the Joule effect being minimized to negligible values. Then second order resonance systems are conceived with grains and defects of alloys and a new influence mechanism of EMP on alloys has been put forward that micro texture at different positions can be disturbed to varying degrees accompanied with defects reconfiguration by nonlinear oscillation. This discovery indicates that EMP can be utilized to modify finished part made of alloys.

Matching Rheology, Conductivity and Joule Effect in PU/CNT Nanocomposites.

We investigated polyurethane (PU)–carbon nanotube (CNT) nanocomposites (PU/CNT) in a range of concentrations from 1 to 8 wt% CNT as hot melt adhesives. We studied the thermal properties of the nanocomposites, which is relevant from an applied point of view. The phase angle plots versus complex modulus results revealed the existence of a maximum above a given CNT concentration. The intensity of the peak and associated relaxation time was analyzed with percolation theory, leading to a new method to determine the rheological percolation threshold. A lower threshold value was obtained from the electrical conductivity data, which was justified recalling that the hopping/tunnelling effect takes place in the nanocomposite, as stated by previous studies in the literature. Joule effect studies indicated that the heating effect was very significant, reaching temperature increases, ΔT, of 60 °C for low voltages. For the first time, the percolation equation was applied to the ΔT to obtain the corresponding threshold. Stimulus-responsive systems were conceived considering the correlation between the ΔT and the conductivity. The case of PU/CNT nanocomposites acting as hot melt adhesives that are welded/unglued by applying/removing an electrical voltage is presented.

Application of an exact integral transform formulation for temperature estimation in solid-state electronics

This work presents an application of an exact analytical approach to estimate the temperature field of solid-state electronics (SSE). A partial lumped approach in the chip’s height was performed, obtaining a two-dimensional mathematical model. The internal heat generation (HG) regions caused by Joule effect due to internal components were modeled as Gaussian functions, and the classical integral transform technique (CITT) was used to solve the problem. The developed formulation was applied in three illustrative HG layouts for chips. In addition, the finite difference method was also implemented for verification and comparison purposes. The CITT provided fast computing and accurate results with small truncation orders in problems with multiple non-uniform heated regions. Furthermore, the formulation presented in this work may be applied to any SSE internal HGs layout, being a useful tool for thermal assessment of SSEs.

R1234ze(E) Flow Boiling inside a 2.5 mm ID Smooth Tube and Comparison against an Equivalent Microfin Tube

The air conditioning and refrigeration industry is now dealing with an imminent substitution of widely implemented refrigerants having a non-negligible global warming impact. Among the proposed hydrofluoroolefins, R1234ze(E) has thermodynamic and transport properties close to those of R134a, and thus it can be one of its substitutes. This paper experimentally analyzes R1234ze(E) flow boiling inside a smooth tube with an internal diameter of 2.5 mm. Mass velocity is investigated from 200 to 600 kg m−2 s−1, for vapor quality from 0.15 to 0.99. The test tube is electrically heated by the Joule effect, by supplying heat fluxes from 12 to 60 kW m−2. Heat transfer coefficients and frictional pressure drops were evaluated from the experimental tests, and compared against values estimated by empirical correlations. Additional experimental tests permitted the comparison between the thermal and hydraulic characteristics of the smooth tube and those of a microfin tube with an inner diameter at the fin tip of 2.4 mm. The comparison revealed the higher contribution of convective boiling for the microfin tube compared to the smooth tube for all of the investigated working conditions.

Maximum Torque Per Watt (MTPW) field-oriented control of induction motor

A new field-oriented control strategy for induction motor is proposed in the paper. It is called Maximum Torque Per Watt (MTPW) and allows obtaining the minimum value of the sum of the stator and rotor losses due to joule effect, and of the iron losses, for a given value of the reference torque and of the motor speed. Iron losses have been modeled according to Steinmetz equation, separating hysteresis and eddy currents and taking into account the dependence both on the frequency and on the peak value of the flux density. Numerical and experimental results are presented to confirm the validity of the proposed approach, which allows achieving significant improvements in the efficiency of induction motor drive.

Electrical Characteristics of HTS Coils With and Without Insulation in a Layer-Wound Configuration

This paper analyses the current distribution in no-insulation (NI) coils in a layer-wound configuration. The investigation aims at comparing the electrical characteristic of two coils wound from the same BSCCO tape, with or without electrical insulation between turns. Both coils are characterized by a very similar geometry, with the same number of turns and layers. Both coils, cooled in liquid nitrogen bath, are charged until the tape critical current is exceeded. To interpret the measurements and analyze the current distribution within the winding, a lumped-parameter equivalent electrical circuit is developed and solved numerically in a time-varying regime. The model results are compared with the signals acquired through voltage taps soldered at the same locations in both coils. Finally, the model is applied to investigate the impact of the transverse contact resistance and to estimate the most stressed locations of the coil during charging, in terms of power produced by Joule effect.

The Application of Ni-Ti SMA Wires in the External Prestressing of Concrete Hollow Cylinders.

An innovative method for prestressing structural elements through the use of shape memory alloys (SMAs) is gaining increasing attention in research as this method does not require the use of mechanical anchorages for tendons. The activation of the memory effect by means of temperature variations (Joule effect) in effect produces high stresses in SMA components attached to concrete components as reported in the literature. This paper presents the work performed for the purpose of prestressing concrete hollow cylinders with the use of nickel–titanium (Ni–Ti) SMA wires. In the tests, a variety of hollow cylinders were made using the same concrete mix and with the same wall thickness (20 mm), but with different external diameters (200 mm, 250 mm, and 300 mm). Their prestressing was achieved by the means of Ni-Ti SMA wires of different diameters (1 mm, 2 mm, and 3 mm) wrapped around the cylinders. Longitudinal and circumferential strain during the thermal activation of the SMA wires by Joule heating was measured using gauges located on the internal surface of the hollow cylinders. The experimental protocol, recorded observations, and discussion of the effectiveness of the prestressing of concrete elements as a function of the test parameters are included in the text in detail. Comments on the conditions for effective prestressing of concrete cylinders with SMA wires are proposed in the conclusions of the paper.

Self-Healing Polymer Nanocomposite Materials by Joule Effect.

Nowadays, the self-healing approach in materials science mainly relies on functionalized polymers used as matrices in nanocomposites. Through different physicochemical pathways and stimuli, these materials can undergo self-repairing mechanisms that represent a great advantage to prolonging materials service-life, thus avoiding early disposal. Particularly, the use of the Joule effect as an external stimulus for self-healing in conductive nanocomposites is under-reported in the literature. However, it is of particular importance because it incorporates nanofillers with tunable features thus producing multifunctional materials. The aim of this review is the comprehensive analysis of conductive polymer nanocomposites presenting reversible dynamic bonds and their energetical activation to perform self-healing through the Joule effect.

Electrical activation and shape recovery control of 3D multilayer woven shape memory polymer composite incorporating carbon fibers

Three-dimensional (3D) reinforced preforms have enormous potential for the development of functional composites by taking advantage of the capabilities of 3D multilayer woven preform design and polymer shape memory behavior. This work aims to investigate the shape memory behavior of thermally active 3D multilayer composite by experimental measurements. The multilayer SMP composite samples comprising an active layer made of carbon fibers are first synthesized. By Joule effect, an internal heat source is created inside the multilayer composites using the active carbon layer. The electrical actuation test results by large bending test method showed that the responses of the SMP composite samples were accurate and the performance was repeatable. This achievement may lead to the application of multilayer SMP composites as electroactive actuators.