Joule Effect Research Articles

Entropy generation analysis in MHD hybrid nanofluid flow: Effect of thermal radiation and chemical reaction

The current study computationally investigates the thermally radiative incompressible flow of hybrid nanofluid induced by a radially stretchable rotating disk with entropy generation analysis. The temperature-dependent viscosity of hybrid nanofluid, stretching of the disk, chemical reaction, Joule, and viscous dissipation effects are incorporated in the formulation of the mathematical flow model. In this study, Karman’s transformations are used to convert the governing equations of partial derivative form into their ordinary derivative form, which is evaluated numerically together with boundary conditions using the BVP Midrich technique built-in Maple software. The impacts of variable viscosity parameter, magnetic field parameter, radiation parameter, Eckert number, Prandtl number, Biot Number, and chemical reaction parameter on flow-field factors and entropy generation rate are presented graphically. The outcomes indicate that higher estimations of magnetic field parameter and entropy generation rate increase the velocity distribution. Also, an increment in Schmidt number and chemical reaction parameter diminishes hybrid fluid concentration, and a higher magnetic field parameter maximizes the same. This study is significant in industrial thermal management and heat transport increment in renewable energy systems.

Evaluation of the gravitational effects on flow boiling heat transfer of R134a in a 0.5 mm tube under conditions of imposed wall-temperature

This paper presents an experimental investigation of heat transfer coefficient and dryout inception during flow boiling of R134a in a circular channel with an internal diameter of 500 μ m for horizontal, 45° inclined, and vertical upward flows. The microchannel was heated by imposing the wall temperature by flowing hot water counter-currently to the test fluid through an annular region containing the test section. Experiments were performed for mass velocities ranging from 350 to 600 kg/(s·m2), heat fluxes up to 46 kW/m2, saturation temperature of 30 °C, and vapor qualities from 0 to 1. The experimental data were parametrically analyzed, and the effects of the experimental parameters (heating method, mass velocity, heat flux, and channel orientation) were identified. Almost similar heat transfer behaviors were found under conditions of imposing wall temperature and heat flux through the Joule effect. The effect of the flow orientation on the heat transfer coefficient prior to the dryout inception was negligible. The heat transfer coefficient increases with increasing vapor quality, heat flux, and mass velocity. The critical heat flux exhibited similar values independently of the flow orientation. Moreover, the critical heat fluxes increases as the dryout inception vapor quality reduces, regardless of the flow orientation.

Application of Thermoelectric Generators for Low-Temperature-Gradient Energy Harvesting

Thermoelectric generators (TEGs) convert a temperature difference into useful direct current (DC) power. TEGs are solid-state semiconductor devices that are generating a lot of interest for energy harvesting purposes in Internet of Things (IoT) applications. This paper analyzes the behavior of state-of-the-art TEGs designed for low temperature gradient operation, with special emphasis on IoT systems for health monitoring for high-voltage alternating current (AC) and DC applications. In such applications, the energy harvesting unit plays a leading role in supplying wireless sensors (WSs). An application example is also presented with the aim to monitor the health condition of devices installed in the tubular busbars found in electrical substations. Since substation busbars heat up due to the Joule effect, there is a small thermal gradient between the busbar and the ambient, so the TEG can convert this heat flow into useful DC energy to supply low-power WSs. This paper assesses the performance of different TEG devices for this application, where very low temperature gradients are expected. The results presented show that with temperature gradients as low as 5 °C it is possible to supply WSs.

Large circular dichroism in the emission from an incandescent metasurface

Compact sources in the mid-wave infrared (MWIR) are needed for applications ranging from spectroscopy to free-space communication. Ultrathin incandescent metasurfaces are promising candidates, offering the possibility to tune the emission spectrum, directivity, and modulation speed. However, control over polarization remains a challenge, especially when it comes to the emission of circularly polarized light. Here, we report the emission of polarized MWIR radiation from a 700 nm thick incandescent chiral metasurface. The degree of polarization is above 0.5 with degree of circular polarization of 0.38 at 5 µm. The metasurface is heated by the Joule effect, and the emission can be modulated beyond 10 MHz. This could enable detection techniques that use polarization as an additional degree of freedom.

Direct electrification of Rh/Al2O3 washcoated SiSiC foams for methane steam reforming: An experimental and modelling study

Electrified methane steam reforming (eMSR) is a promising concept for low-carbon hydrogen production. We investigate an innovative eMSR reactor where SiSiC foams, coated with Rh/Al2O3 catalyst, act as electrical resistances to generate the reaction heat via the Joule effect. The novel system was studied at different temperatures, space velocities, operating pressures and catalyst loadings. Thanks to efficient heating, active catalyst and optimal substrate geometry, complete methane conversions were observed even at a high space velocity of 200000 Nl/h/kgcat. A specific energy demand as low as 1.24 kWh/Nm3H2, with an unprecedented energy efficiency of 81%, was achieved on a washcoated foam with catalyst density of 86.3 g/L (GHSV = 150000 Nl/h/kgcat, S/C = 4.1, ambient pressure). A mathematical model was validated against measured performance indicators and used to design an intensified eMSR unit for small scale H2 production.

Porous functional materials with excellent solar-thermal and electro-thermal properties for desalination of saline water

Desalination of saline water is a key technology to produce safe drinking water. Here, we report a novel type of reduced graphene oxide (GO) nanosheets modified porous functional materials (rGS) with both excellent solar-thermal and electro-thermal properties for efficient, portable, and continuous desalination of saline water. The rGS porous materials are prepared by modifying porous melamine sponges with GO nanosheets, and then reducing GO nanosheets into reduced GO (rGO) nanosheets. With sufficient rGO nanosheets coated on rGS porous materials, water evaporation fluxes of rGS-5 porous materials are > 1100 g m-2h−1 in solar-thermal desalination under 1000 W m−2 and > 3600 g m-2h−1 in electro-thermal desalination under direct voltage of 20 V due to the excellent solar-thermal property and Joule effect of rGS. The salt rejection values are always higher than 99.95% towards different saline waters including hypersaline water, and the salinities of distilled waters are always far lower than the WHO standard for safe drinking water. The strategy and results in this work provide valuable guidance for designing portable desalination systems to produce safe drinking water by simply using solar energy and/or direct-current power supply in certain applications with special needs such as remote regions and disaster situations.

Energy Consumption Analysis of a Continuous Flow Ohmic Heater with Advanced Process Controls

This paper presents an analysis of the energy consumption of a continuous flow ohmic heater (CFOH) with advanced process controls for heating operations in the food and drinks industry. The study was carried out by using operational data collected from a CFOH pilot plant that was designed and constructed at the National Centre of Excellence for Food Engineering (NCEFE), Sheffield Hallam University. The CFOH is controlled by a PC and includes an onboard Programmable Logic Controller (PLC) and a Human Machine Interface (HMI) so that it can be operated as a stand-alone unit with basic on/off and power setting control but without any advanced control features. The technical solution presented in this paper for heating foods demonstrates significant energy saving compared with conventional heating methods. Using the CFOH, the electric current generated in the food products by the Joule effect produces a rapid temperature increase with very high energy efficiency. This technique eliminates the low efficiency of heat transfer from the surface of vessels typically used to heat and cook food products. The analysis presented in this paper describes the energy consumption of the CFOH and compares the efficiency of the CFOH when different advanced process control techniques are used. Experimental results and analysis have shown that the CFOH can achieve an energy efficiency conversion of at least 87.9%. It has also shown that the energy conversion percentage can be increased by applying advanced controllers such as model predictive control (MPC) or adaptive model predictive control (AMPC).

Magnetic and electrically conductive polyurethane composites with high content of two functional fillers base on “Root” inspired microstructure

The incorporation of functional fillers into polymer matrix endows composites with functionality, and filler content is an important factor that affects the performance and functionality of composites. In traditional processing methods, excessive filler usually deteriorates the continuity of polymer matrix, leading to composite developing crack or failing to support itself. Hence, the filler content cannot be usually maximized. Not to mention, the incorporation of two functional fillers with large quantity to achieve multi-functionalities. In this work, branched polyurethane (PU) dendrites with large aspect ratio and interpenetrating entangled structure are used to capture functional fillers. By introducing carbon nanotubes (CNTs) and carbonyl iron particles (CIPs) onto these “root” inspired dendritic PU, the resultant PU/CIPs/CNTs composite with PU:CNTs:CIPs weight ratio at 1:0.3:7 demonstrates excellent electrical conductivity of up to 5.2 S/cm, ferrimagnetic property >181.2 emu/g and favorable flexibility. The satisfactory conductivity endows composite the capacity to generate heat as a bias voltage applied according to Joule's law, and saturate temperature of 138.9 °C is developed under 3 V-voltage. Extensive magnetic responses are observed due to the extremely high ferrimagnetism. In combination with conductive property and flexibility, fascinating applications such as magnetic field sensor, magnetic controlled heating and switch are demonstrated, revealing wide promising application prospects of composites especially in flexible multifunctional electronics.

On the fully coupled quasi-static equations for the thermoelastic halfspace

Influence functions for fully coupled quasi-static thermoelasticity are presented. They can be used to calculate displacements, stresses as well as temperature distributions within a halfspace for arbitrarily shaped and time dependent heat sources or pressure distributions on the surface. To this end, the underlying equations are solved for a mechanically or thermally loaded rectangular element on the surface by potential theory. The solution procedure is described in detail. The obtained results are verified and may easily be transferred to the theory of poroelasticity where the underlying equations are structurally equal. Example calculations for a parabolic pressure field, heat flux and temperature field are performed and simulation results are discussed particularly in comparison to the uncoupled case. Estimations of the extent to which the Gough–Joule effect and its consequences can be neglected are given.

Joule heating involving ion currents through channel proteins.

Ion currents associated with channel proteins in the presence of membrane potential are ubiquitous in cellular and organelle membranes. When an ion current occurs through a channel protein, Joule heating should occur. However, this Joule heating seems to have been largely overlooked in biology. Here we show theoretical investigation of Joule heating involving channel proteins in biological processes. We used electrochemical potential to derive the Joule's law for an ion current through an ion transport protein in the presence of membrane potential, and we suggest that heat production and absorption can occur. Simulation of temperature distribution around a single channel protein with the Joule heating revealed that the temperature increase was as small as <10-3 K, although an ensemble of channel proteins was suggested to exhibit a noticeable temperature increase. Thereby, we theoretically investigated the Joule heating of systems containing ensembles of channel proteins. Nerve is known to undergo rapid heat production followed by heat absorption during the action potential, and our simulation of Joule heating for a squid giant axon combined with the Hodgkin-Huxley model successfully reproduced the feature of the heat. Furthermore, we extended the theory of Joule heating to uncoupling protein 1 (UCP1), a solute carrier family transporter, which is important to the non-shivering thermogenesis in brown adipose tissue mitochondria (BATM). Our calculations showed that the Joule heat involving UCP1 was comparable to the literature calorimetry data of BATM. Joule heating of ion transport proteins is likely to be one of important mechanisms of cellular thermogenesis.

Optimal Dispatch of Battery Energy Storage Considering Cycling and Calendar Ageing

The growing share of renewable energy sources in the energy mix and the liberalization of electricity markets drastically affected the operation of electricity generators. This transition from fossil fuel-based energy systems to renewable ones will significantly change the energy market, giving important opportunities for energy storage systems. In the next years, a large amount of storage capacity is foreseen to be integrated into the electricity grids to shave the demand peaks, mitigate price volatility, and provide services to the grid. In such a situation, to properly manage these crucial technologies, and thus guarantee the economic viability of the operation, it is essential to properly optimize the dispatch and define the best scheduling. This paper considers Battery Energy Storage (BES) to study the problem of dispatch optimization of storage technologies. The complete model of BES is developed, considering especially the effect of DoD (Deep of Discharge) on the total number of cycles, that influence significantly the degradation, and the influence of the current-rate on the total efficiency, due to the effects of losses for the Joule effect. The implemented optimization is based on a Mixed Integer Linear Programming (MILP) approach, the discretization of the state of charge (SoC), and the continuous update of rated capacity until the maximum admissible fade is reached. Different scenarios are compared showing how the effectiveness of the proposed approach at maximizing the net operational profits or minimizing the loss depending on the profitability of markets.

A SIMPLE STUDY OF JOULE HEATING EFFECT IN ARGON DBD REACTOR

Study of the gas heating phenomenon due to the heat joule effect in plasma created by an argon dielectric barrier discharge (DBD) reactor operating under treatment surface and medical sterilization conditions is essential to find the optimum of DBD discharge functioning. The present investigation of the influence of gas heating on argon discharge characteristics was executed by a one-dimensional fluid model. The gas temperature development in the DBD discharge was determined by the heat conduction equation. To consider the joule heating effect, the heat transport equation was solved along the gap distance of discharge. The results obtained from the coupling of a 1D fluid model with the heat conduction equation allowed us to calculate the gas temperature profile of argon in the DBD and plasma physical characteristics such as the densities of charged particles, the voltages, the electric field, and the coefficient rate of the ionization, attachment, and recombination in order to analyze the gas temperature development in argon DBD.

Development of Multicellular Converter with Magnetic Coupler for Space Charge Measurement on DC Cable

One of the main issues on high voltage direct current (HVDC) cable is the electric field distribution on the insulation induced by space charges accumulation. Indeed, the space charges can cause a local increase of the electric field, which will accelerate ageing and may lead to dielectric breakdown. The TSM is one of the techniques that allow space charge measurements. The principle of the TSM consists in disturbing the electrostatic balance of the cable insulation system using a short thermal stimulus. For this study, the thermal pulse is created by Joule effect. This paper describes the structural optimization of a multi-cell DC-DC converter and its use in a high-current application to produce thermal stimulus. The design of the converter is first presented, then a multi-objective optimization is proposed for minimizing volume and losses. Finally, experimental results using a converter prototype which confirmed the space charge measurement principle are presented.

A Flexible Wearable Thermography System Based on Bioheat Microsensors Network for Early Breast Cancer Detection: IoT Technology

Many women diagnosed by traditional screening methods, such as palpation, mammography, and MRI, do not discover their cancer until it is relatively advanced. This makes treatment more difficult and reduces the chance of a cure. To deal with this issue, we have developed a noninvasive embedded thermography system that allows for an early detection of breast cancer. Indeed, the surface temperature distribution of the breast, which we will call the thermal image, can be used as a preventive indicator of the subsequent development of a cancerous tumor. This is due to the metabolic activity of the immune system, which induces, in the presence of cancer cells, a local increase of temperature even before the tumor tissue is differentiated and detectable by conventional imaging systems. The proposed system is designed as a network of bioheat microsensors applied to the breast, to measure periodically the temperature gradients on the surface. All the bioheat microsensors are addressed by a microcontroller via the I2C protocol. To calibrate and evaluate the proposed system, we have proposed an experimental model of the breast, inside which we have placed Joule effect heating elements.

Engine Combustion Network “Spray G”: Wall heat transfer characterization by infrared thermography

Nowadays, several efforts are being made to design more efficient, cleaner, and economically accessible engines. Spray-wall interactions are strongly related with the fuel–air mixture and emission formation. As such, they are considered as the most important physical processes in engine research. In the present study, the infrared thermography coupled with an inverse heat transfer data reduction is applied to evaluate the wall heat transfer of an iso-octane spray generated by a multi-hole gasoline direct injector (Spray G) impinging on a heated thin foil. The experimental apparatus includes an Invar foil (50μm in thickness) heated by Joule effect and the injector located at 66.66 injector nozzle diameter above the surface. Thermal images of the impinging spray are acquired from the dry side of the foil at several time delays from the start of injection at two different injection pressures (10and 20MPa) and two different wall temperatures (373and 473K). The experimental data are reduced in the dimensionless form in terms of the spray cooling efficiency ξ, which represents the ratio between the spray cooling heat flux and the heat transfer capability of the fluid, by taking into account the area of impact of the spray. Results show a substantial increment of the heat flux and the spray cooling efficiency by increasing the wall temperature. Also, the increment of the injection pressure has an increasing effect on the area of impact, the heat flux, and the efficiency of the spray for both wall temperatures investigated in the experimental campaign. The spray cone angle and the plume jet axis angle were also estimated from the wall heat flux distribution.

Fractal structure change of pitch-based carbon fiber during high-temperature heat treatment

High-temperature treatment (HTT) is a vital process to change the structure and improve the performance of pitch-based carbon fiber. The complexity of pore structure and their change during heating can be described by a mathematical concept of fractal. This short contribution reports an in-situ synchrotron radiation small angle X-ray scattering (SAXS) study on the fractal structure change of a kind of pitch-based carbon fiber during heating from 1200 °C to 1700 °C with Joule effect in a small furnace. The change of the fractal structure at different azimuth angles with temperature is revealed, and the corresponding mechanism is analyzed.

The Synchronous Electric Machine with Variable Geometry Done by Elastic Permanent Magnets

Abstract The paper refers to an electric machine (motor/generator) with an adjustable magnetic field, because its rotor has a special construction that allows the deformation of its elastic permanent magnets. The permanent magnets deform due to a clamping stroke parameter and in this way the flux density of the magnetic field as well as the width and length of the permanent magnets are variable. The variable magnetic field crosses the stator coils which are supplied by the voltages and due to a variable magnetic flux density, a higher torque will result even at lower values of the currents. As a result, a higher efficiency will be obtained due to the increase in mechanical power and the decrease in losses (e.g., Joule effect) in the stator windings. The presented electric machine is a synchronous machine with variable geometry, belonging to the category of permanent magnet machines. Specific to this machine is the fact that the rotor magnets are elastic, being made of ferritic compound rubber with neodimium magnets N45.

Coupled flow in saturated soil around a vertical grounding rod HVDC considering underground water's action

• Coupled fluxes in soils due to current injection into HVDC ground rods are analyzed. • Phenomenon involving the fields of electromagnetism, thermal and hydraulics. • It takes into account the effect of an underground flow. • Results include temperature, velocity and pore pressure in a stratified saturated soil. The phenomenon of coupled fluxes in soils given the injection of current in HVDC (High Voltage Direct Current) ground rods is a multiphysics problem, involving different fields, including electromagnetism, thermal and hydraulics. In some regions where precipitation is intense or due to the presence of an aquifer, the saturated condition of the soil is particularly important for the analysis of the behavior of the environment, based on the active flows. In this study, the water velocity around the ground rod is investigated, as well as the pore pressure and temperature in a transient regime, considering the Joule effect, the performance of the electro-osmotic flow and the action of the underground velocity. Such phenomena are involved by temperature-dependent parameters. The study methodology is based on simulations adopting the finite element method for the coupling of physics in a saturated and stratified soil. The validation of the results for the Joule effect shows a maximum temperature error in the order of 3.3%. As a result, it was possible to infer, through a parametric sweep, the parameters that most favor the increase in temperature, velocity and pore pressure in the medium porous. The results presented serve as a reference for HVDC grounding system designs.

CFD investigation of the radiative heat transfer effects on the adoption of an electrical heated catalyst to increase the abatement efficiency

The thermal transient of the after-treatment system (ATS) during the cold start and the typical urban drive low load engine operations is a crucial point for the conversion efficiency. In this context, the adoption of electrical heating is regarded as an effective solution to promote the catalytic activity and the pollutants abatement. This paper focuses on the evaluation of the radiative heat transfer affecting the operation of an electrical heated catalyst employed to increase the abatement efficiency of a standard catalyst. The modeling methodology relies on a CFD framework based on a Conjugate Heat Transfer (CHT) approach in OpenFOAM, so that a detailed characterization of the thermal transient of the different components of the exhaust line can be achieved. The electrical heating device under investigation is based on a metallic support and it is heated by the Joule effect. The distribution of the heat and its subsequent interaction with the gas flow significantly influence the catalyst operations. In this context, the CFD modeling framework has been further developed so that it is possible to accurately evaluate the radiative heat transfer in correspondence of the porous regions. The description of such features is mandatory for an accurate prediction of the maximum electrical heating device temperatures, resulting in a reliable estimation of the gas flow temperature and its subsequent interaction with the catalyst. The simulation methodology has been applied at first excluding the radiative heat transfer. Then, the developed radiation modeling is applied, so that its influence on the ATS performance can be fully evaluated.

Evaluation of the Percentage of Crown Effect Losses on the Whole Cameroonian Transmission Network Compared to the Joule Effect Losses

In this paper, we have estimated the losses on the electric transmission lines of the Cameroonian Southern Interconnected Network (RIS) and Northern Interconnected Network (RIN) by collecting data on the network and line parameters for the 225 kV circuit of the RIS and 110 kV circuit of the RIN from Energy of Cameroon (ENEO) on the one hand; on the other hand, we have carried out simulations while studying the influence of the different parameters such as the transported power, the meteorological conditions, the characteristics of the network and the transport distance on the electric losses in our different transmission lines. This was achieved through a thorough review of technical loss analysis methods, conducting power loss studies on each 225 kV RIS and 110 kV RIN line, using appropriate mathematical models for power line loss assessment, graphical interpretation of the various simulated models, and quantitative loss assessment. It was found that crown losses are about 2.55 times higher in the RIS than in the RIN; poor weather conditions and the level of voltage carried favour crown discharge, thus increasing losses. As for the Joule effect losses, they are about 6.54 times higher in the RIS than in the RIN. From this study, we can see that on the whole of the Cameroonian electricity network, crown losses are negligible compared to joule losses.