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This research looks at the impact of dielectric fluids and fluid speeds on cell temperature control in innovative cylindrical lithium‐ion batteries during high‐rate discharges (C‐rate) using the multiscale multidomain battery model. The goal is to improve the battery thermal management system to increase battery performance, longevity, and safety. The present study includes reducing thermal strains, enhancing efficacy, and forestalling overheating risks across various applications in electrified systems. The assessment focuses on four dielectric fluids—ester, mineral, kerosene, and Novec 7200—flowing at 0.01 m/s to gauge their efficiency in managing cell temperatures. Results demonstrate the criticality of effective thermal management in maintaining optimal battery performance and longevity. Ester oil emerges as the most efficient coolant, maintaining cell temperatures at 305.84 K and showcasing a 44% reduction compared with scenarios without coolant. In contrast, kerosene oil, mineral oil, and Novec 7200 yield temperature reductions of 42.86%, 42.51%, and 43.11%, respectively. Furthermore, combining 1% v/v. MXene nanoparticles with ester oil enhance cooling capabilities, with remarkable cell temperature reductions of 50% at 0.01 m/s velocity. Subsequent increments in flow velocity lead to enhanced cooling effects: at 0.05 and 0.1 m/s, reductions reach 51.89% and 52.155%, escalating to 52.58% and 54% at 0.5 and 1.0 m/s, correspondingly. [ABSTRACT FROM AUTHOR]

A novel concentrating photovoltaic-thermal solar collector was designed, fabricated and experimentally investigated at the University of Lleida, in Spain. Two designs based on two dielectric liquids, isopropyl alcohol (IPA) and deionised water (DIW), were developed. In both cases, the solar cells were directly liquid-immersed. The study includes experiments and numerical simulations. The proposed concentrator was incorporated into a testing unit to examine its potential as a façade by controlling light and thermal flux transmitted into a building. The results show promising electrical performance and acceptable thermal performance, with thermal losses ranging from 14 to 20 W °C−1m−2. The optical efficiency was around 73% in the case of the concentrator with DIW and about 76% for the one with IPA. Regarding electrical performance, the fill factors for IPA and DIW configurations are as follows: 62.8% and 61.7%, respectively. The comparison results reveal striking differences between the testing unit with and without solar concentrators, with the concentrator-equipped unit showing around four times lower illuminance and a 50% reduction in maximum heat fluxes and interior temperature. Generally speaking, it can be said that these energy-generating façades show satisfactory behaviour and offer interesting possibilities for building-integrated applications. [ABSTRACT FROM AUTHOR]

It is proved analytically that the complex growth rate n = nr + ini (nr and ni are the real and imaginary parts of n , respectively) of an arbitrary neutral or unstable oscillatory disturbance of growing amplitude in rotatory electrothermoconvection in a dielectric fluid layer saturating a sparsely distributed porous medium heated from below, for the case of free boundaries, is located inside a semicircle in the right half of the nrni − plane, whose centre is at the origin and radius = max T a P r 2 , R ea P r A , where Ta is the modified Taylor's number, Pr is the modified Prandtl number, Rea is electric Rayleigh number and A is the ratio of heat capacities. The upper limits for the case of rigid boundaries are derived separately. Furthermore, similar results are also derived for the same configuration when heated from above. [ABSTRACT FROM AUTHOR]

Electric Discharge Machines (EDM) have been advanced in several fields to cut and model different metal shapes. Considering this advancement, the presented research article has aimed to improve EDM performance by the optimal dielectric fluid section. Several procedures were implemented to maximize EDM performance in the past, but the appropriate Metal removal rate (MRR) still needs to be found. So, a novel African Buffalo Optimization (ABO) is utilized in EDM research to attain the optimal outcome. In addition, the Ti–6Al–4V metallic, nano aluminium powder and copper powder with dielectric fluid (mineral oil and Kerosene) have been utilized for gaining less error rate and high tool wear rate, and Pulse on the rate. The copper powders are 99.98% pure with 1 kg of powder and are used in EDM. Using African Buffalo Optimization (ABO), the material removal rate and desirability are assessed hybrid. Moreover, the developed technique is implemented in MATLAB. Hence, the designed novel optimized dielectric fluid EDN has produced 33% MRR, 1% pulse on rate and 1.1% error score. These obtained outcomes are better than the compared traditional approaches. Hence, the proposed EDM is significant in practical applications by cutting the metal with high MRR. [ABSTRACT FROM AUTHOR]

In the current research work, in-house developed and fabricated multi-axis near-dry Electrical Discharge Machine (near-dry EDM) has been used having different tool positions, i.e. tool electrodes in horizontal position (Case-I) and vertical positions (Case-II) as a novel machining techniques in hard-to-reach places and also to improve the process performance. Design of Experiment tool has been used with three process parameters: voltage, discharge current, and pulse-on-time for experimentation purposes. In order to maximize Material Removal Rate (MRR), it was necessary to compare and enhance these parameters in both cases, i.e. Case-I, and Case-II. The machining process is significantly influenced by the vertical tool positions, as indicated by the largest percentage contribution in the Analysis of Variance results. The voltage has the least influence, while the pulse-on time is relatively less. In contrast, for the horizontal tool position, the voltage proved the most prominent factor in terms of influence, while the current ranked second in significance. Conversely, the pulse-on time exhibited the least impact among the three factors. The highest MRR 2.45 mm3/min was achieved in the vertical tool position while in horizontal machining, the highest MRR 0.144 mm3/min was observed. These findings provide valuable insights into the multi-axis near-dry EDM with proposed methodology. [ABSTRACT FROM AUTHOR]

Abstract Nitinol, a biocompatible material, is gradually becoming famous for its superelasticity, shape memory and corrosion resistance behaviours. However, the lower machinability due to the strain-hardening effect and lower thermal conductivity is contrary to its adventitious properties. Therefore, EDM is a preferable machining process for materials like Nitinol. EDM, thermal processing, raises the concern of processing Nitinol with minimal variation of its well-known properties and economical machining process. Therefore, this article deals with multi-objective optimization through GRG-assisted GA of µ-EDM drilling of Ni51.58Ti48.34 alloy using a copper electrode and distilled water. It was found that discharge current and servo voltage significantly influence the responses. The GA, with the assistance of GRG, optimized the multiple responses (viz. MRR, TWR and DoT) and yielded a discharge current of 12 A, gap voltage of 40 V, discharge time of 2 µs, charging time of 9 µs and flushing pressure of 50 kg/cm2. The confirmatory experiment yielded MRR of 0.0036 g/min, TWR of 0.0038 g/min and DoT of 0.0089 radians. There were variations of the predicted and experimentally validated responses by − 2.78, 26.32 and 35.96% for MRR, TWR and DoT, respectively.

The onset of convective instability in an internally heated dielectric fluid‐saturated porous layer under the influence of a uniform AC electric field for different types of boundary conditions is investigated. The flow in the porous medium is described by the Brinkman model with fluid viscosity different from effective viscosity. The lower adiabatic and the top with finite heat transfer coefficient to the external environment boundaries are considered to be either rigid or stress‐free. The presence of a uniform volumetric heat source alters the conduction profile of the temperature field from linear to quadratic in the vertical coordinate. A modal linear stability analysis of the basic motionless state is carried out and the general regime of linear instability is investigated by solving the stability eigenvalue problem numerically using the Galerkin method of weighted residual technique. The neutral stability condition as well as the critical value of the thermal Rayleigh number is computed for rigid–rigid, free–free, and rigid–free boundaries for various values of governing parameters. It is seen that the nature of boundaries affect the stability of the system only quantitatively, though not qualitatively. The rigid–rigid boundaries offer a more stabilizing effect against convection in comparison with rigid–free and free–free boundaries. The study found that the effect of increasing thermal electric Rayleigh number and the Darcy number is to hasten the onset of instability, while the opposite trend is perceived with an increase in the ratio of viscosities and Biot number. The outcomes of this investigation are found to be in good agreement with past studies under the limiting cases. [ABSTRACT FROM AUTHOR]

The electrothermoconvection in a rotating dielectric fluid layer heated from below (or above) is studied analytically using linear stability theory. First, we derive the necessary conditions for oscillatory motion when the fluid layer is heated from below and from above. Then as a consequence, sufficient conditions for the validity of the exchange principle are derived for the two configurations in terms of the parameters of the systems alone. The results hold for free boundaries for all wave numbers and for rigid boundaries with some restrictions. Further, the results for electrothermoconvection without rotation, rotatory Rayleigh–Bénard convection and Rayleigh–Bénard convection are also obtained as special cases which validate the existing results. To the best of author's knowledge such results are not reported in the literature as far as the domain of electrothermoconvection studies is concerned. [ABSTRACT FROM AUTHOR]

Nitinol, a biocompatible material, is gradually becoming famous for its superelasticity, shape memory and corrosion resistance behaviours. However, the lower machinability due to the strain-hardening effect and lower thermal conductivity is contrary to its adventitious properties. Therefore, EDM is a preferable machining process for materials like Nitinol. EDM, thermal processing, raises the concern of processing Nitinol with minimal variation of its well-known properties and economical machining process. Therefore, this article deals with multi-objective optimization through GRG-assisted GA of µ-EDM drilling of Ni51.58Ti48.34 alloy using a copper electrode and distilled water. It was found that discharge current and servo voltage significantly influence the responses. The GA, with the assistance of GRG, optimized the multiple responses (viz. MRR, TWR and DoT) and yielded a discharge current of 12 A, gap voltage of 40 V, discharge time of 2 µs, charging time of 9 µs and flushing pressure of 50 kg/cm2. The confirmatory experiment yielded MRR of 0.0036 g/min, TWR of 0.0038 g/min and DoT of 0.0089 radians. There were variations of the predicted and experimentally validated responses by − 2.78, 26.32 and 35.96% for MRR, TWR and DoT, respectively. [ABSTRACT FROM AUTHOR]

The use of natural esters as an insulation medium in transformers is well known. This paper proposes to use Baobab oil (Adansolia digitata) as insulator. The Baobab oil is modified using the additives such as hydrocarbon -C12H26-C15H32 (AD1) and aluminium-II-oxide (AD2) of size 10 nm. The modified natural ester (NE) called nano natural ester (NNE) shows good dielectric strength at 7.5 mL/L of AD1 and 0.75 g/L of AD2. NNE is prepared by blending AD1 and AD2 using ultrasonic waves. Here, in NNE, AD1 serves as thinner, and AD2 acts as electron scavenger. The NNE is then subjected to accelerated heasting at 100 °C for 720 h. The dielectric properties like AC breakdown voltage, fire point, kinematic viscosity (at 30 °C), acid number and water content are measured at 120 h. The data is then used as an input to Euler's method (EM) for predicting the ageing rate for 1440 h. The prediction results of EM are confirmed using the artificial neural network (ANN); ANN shows significantly less deviance. The prediction results of NNE, NE and conventional insulating fluid (CIF) like mineral oil are compared, which indicates that NNE ages at a slower rate than CIF. Under lower temperature loading, NNE ages slower than the predicted results and shows endurance beyond 2880 h. Hence, the use of NNE is a cost-effective and suitable solution to insulating fluids in power and distribution transformers. [ABSTRACT FROM AUTHOR]

Micro Electro-Discharge Machining is a precision machining process that uses electrical discharge to produce small-scale components with high accuracy. A metal workpiece is machined in this process by repeatedly generating spark between a tool electrode and the workpiece, removing material in a controlled manner. The significance of µ-EDM lies in its ability to produce highly accurate and complex components with a high surface finish, making it ideal for use in various industries, including aerospace, medical, and electronics. The critical parameters to the success of µ-EDM include the electrical discharge energy, voltage, current, pulse duration, and spark gap between the tool electrode and workpiece, including the shape and size of the tool electrode. This review article discusses the µ-EDM process used to machine biological materials and also examines the µ-EDM, dry µ-EDM procedure, and the features of biomedical materials for biocompatibility, 3D micro shape machining with tool wear composition, and thin film coating for microelectrodes. The impact of introducing nanoparticles to dielectric fluids is further clarified in this article. This study addresses the prospective future research subjects and application areas for the µ-EDM process in order to fulfill the demanding criteria for biomaterials and their usage in the production of bioimplants. [ABSTRACT FROM AUTHOR]

Localized boiling and enclosed condensation of a dielectric liquid in a thermosyphon can be used as an alternative to traditional air cooling for high performance microprocessors. A small quantity of dielectric fluid boils at the surface of the microprocessor and is condensed by a heat exchanger, which removes the heat from the system. Here, the heat exchanger was a water-fed cold plate cooling a round fins heat sink. Such a thermosyphon can remove large heat fluxes and increase the energy efficiency of data centers.An experimental setup was built to measure the impact of various operating parameters on the thermal resistances of the thermosyphon. The thermal resistances that were considered were the boiling resistance between the heater and the dielectric fluid, the condensation resistance between the dielectric fluid and the cold water feeding the cold plate, and their sum (the total thermal resistance). The operating parameters tested were the cold plate inlet flow rate (0.2 L/min and 1 L/min), the cold plate inlet temperature (15 °C and 24 °C) and the filling ratio of the enclosure (33 %, 66 % and 88 %).It was observed that changing the filling ratio did not have a significant impact on the thermal resistances of the thermosyphon. Increasing the cold plate inlet flow rate from 0.2 L/min to 1 L/min and decreasing the cold plate inlet temperature from 24 °C to 15 °C both led to significantly lower total thermal resistance. However, increasing the flow rate lowered the rate at which the pressure increased with the amount of heat removed from the system, while this rate did not change when decreasing the cold plate inlet temperature.These observations could be properly explained by a simple analytical model, with a single free parameter (increasing the thermal resistance of the heat sink for the lowest cold plate flow rates). With the free parameter adjusted to the data, the model had a root-mean square error of 1.8 °C and a maximum error of 6 °C, over all measured conditions.This study demonstrates how changing the filling ratio or the cold plate inlet temperature and flow rate have an impact on the pressure, the temperature and the thermal resistances inside the thermosyphon. This is a first step in evaluating the energetic and economic efficiency of the thermosyphon solution for its future integration in data centers.

This paper explores two-phase immersion cooling using sealed enclosures of dielectric fluid as a technique to achieve compact, power dense converters on a single printed circuit board (PCB). The proposed approach employs passive circulation of the fluid and does not introduce system complexity beyond a heat exchanger required to condense the vapour. A test apparatus representing six 650 V, 150 A semiconductor switches in an inverter rejecting heat to a 65$\,^{\circ }$C water cooling loop is developed. Pool boiling experiments on a flat surface in Novec 7000 dielectric fluid demonstrate critical heat flux of 43 W cm$^{-2}$ at a saturation temperature of 94$\,^{\circ }$C and a corresponding pressure of 593 kPa. By augmenting the surface with pin fins (representative of a heat spreader attached to a switch) and grit blasting to improve the surface micro-geometry, the maximum heat transfer coefficient increased from 1.5 W cm$^{-2}$ K$^{-1}$ to 3.4 W cm$^{-2}$ K$^{-1}$ with a corresponding reduction in switch temperature from 125$\,^{\circ }$C to 107$\,^{\circ }$C at the total power dissipation of 186 W. A practical implementation with comparable thermal performance to the experimental apparatus but minimised volume of 0.12 L is presented. This yields a Cooling System Performance Index of 37 WL$^{-1}$ K$^{-1}$, including the heat exchanger and printed circuit board with switches, decoupling capacitors and gate drivers.

In this investigation, the surface characteristics of Nickel based superalloy Inconel-625 were evaluated by the electrical discharge machining with used cooking oil-based biodiesel as a dielectric. Nickel-based superalloys find wide applicability in numerous industries due to their specific properties. The Cu electrodes of various densities prepared by atomic diffusion additive manufacturing process were used for machining. A comparison of the performance was made based on average surface roughness. The Design-expert software was used for experimental design and parametric analysis. The outcome demonstrated that bio-dielectric fluid produced improved surface characteristics. The surface roughness was observed to reduce. The surface micrograph obtained from scanning electron microscopy also confirms a better surface finish of bio-dielectric fluid over EDM oil. The surface roughness was shown to be most significantly influenced by the discharge current, with the other parameters having little or no effect. The results showed that for bio-dielectric, the lowest Ra was 0.643 µm, and for EDM oil, the highest value of 0.844 µm. The slightest difference in roughness value for two dielectric fluids was 0.013 µm, and the highest difference was 0.115 µm.

A novel concentrating photovoltaic-thermal solar collector was designed, fabricated and experimentally investigated at the University of Lleida, in Spain. Two designs based on two dielectric liquids, isopropyl alcohol (IPA) and deionised water (DIW), were developed. In both cases, the solar cells were directly liquid-immersed. The study includes experiments and numerical simulations. The proposed concentrator was incorporated into a testing unit to examine its potential as a façade by controlling light and thermal flux transmitted into a building. The results show promising electrical performance and acceptable thermal performance, with thermal losses ranging from 14 to 20 W °C−1m−2. The optical efficiency was around 73% in the case of the concentrator with DIW and about 76% for the one with IPA. Regarding electrical performance, the fill factors for IPA and DIW configurations are as follows: 62.8% and 61.7%, respectively. The comparison results reveal striking differences between the testing unit with and without solar concentrators, with the concentrator-equipped unit showing around four times lower illuminance and a 50% reduction in maximum heat fluxes and interior temperature. Generally speaking, it can be said that these energy-generating façades show satisfactory behaviour and offer interesting possibilities for building-integrated applications.

Transparent and flexible vibrotactile actuators play an essential role in human–machine interaction applications by providing mechanical stimulations that can effectively convey haptic sensations. In the present study, we fabricated an electroactive, flexible, and transparent vibrotactile actuator with a dielectric layer including a dielectric elastomer and dielectric fluid mixture. The dielectric fluid mixture of propylene carbonate (PC) and acetyl tributyl citrate (ATBC) was injected to obtain a transparent dielectric layer. To further improve the haptic performance, different weight ratios of dielectric fluid (PC: ATBC) were injected. The fabricated vibrotactile actuators based on a transparent dielectric layer were investigated for their electrical and electromechanical behavior. The proposed actuators generate a large vibrational intensity (~2.5 g) in the range of 200–250 Hz. Hence, the proposed actuators open up a new class of vibrotactile actuators for possible use in various domains, including robotics, smart textiles, teleoperation, and the metaverse. [ABSTRACT FROM AUTHOR]

The area of metallurgy has witnessed many advancements in the development of novel electrically conductive materials that shows exceptional mechanical as well as thermal properties. Nonetheless, traditional machining techniques encounter difficulties while machining hard materials. In order to address this limitation, electrical discharge machining (EDM) has emerged as a widely utilised method for machining of intricate geometries and the hard materials. EDM is a category of thermo-electric process that employs rapid recurring sparks between the electrode and work material, eroding the material without direct contact. As there is no contact between the electrode and work material, the issues related to machining defects such as mechanical stresses, clattering, and vibration eliminates. However, EDM have some limitations like poor surface finish and low volumetric material removal. To overcome these kind of limitations, the introduction of metallic powder into the dielectric fluid has been explored in powder-mixed electric discharge machining (PMEDM). This introduction of powder during the process leads to enhance the conductive strength of the fluid and increases the spark gap distance between the electrode and counter material. The inclusion of powder has a significant impact on the performance of the EDM process. Hence, this review aims to facilitate researchers in comprehending the concept of PMEDM and to examine the process parameters required to achieve improved levels of quality. [ABSTRACT FROM AUTHOR]

The role of a uniform AC electric field and a nonuniform volumetric heat source arising due to an external incident radiation on the onset of Marangoni convection in a horizontal layer of an incompressible dielectric fluid is investigated. The bottom rigid surface is fixed at a constant temperature while the top free surface at which the surface tension acts is considered to be nondeformable and a Robin boundary condition on the perturbation temperature is invoked. The nonuniform internal heating within the fluid layer alters the conduction temperature profile from linear to nonlinear in the vertical coordinate. The linear stability of the quiescent basic solution is studied with respect to normal mode disturbances. The resulting stability eigenvalue problem with variable coefficient is solved numerically using the Galerkin method. The impact of governing parameters on the instability of the system is discussed thoroughly. The forces causing instability reinforce together and are found to be tightly coupled. It is observed that the strength of nonuniform heat source and the electric Rayleigh number is to hasten, while an increase in the Biot number is to delay the onset of Marangoni electroconvection. Finally, the results obtained under the limiting cases are shown to be in good agreement with those published earlier. [ABSTRACT FROM AUTHOR]

In this investigation, the surface characteristics of Nickel based superalloy Inconel-625 were evaluated by the electrical discharge machining with used cooking oil-based biodiesel as a dielectric. Nickel-based superalloys find wide applicability in numerous industries due to their specific properties. The Cu electrodes of various densities prepared by atomic diffusion additive manufacturing process were used for machining. A comparison of the performance was made based on average surface roughness. The Design-expert software was used for experimental design and parametric analysis. The outcome demonstrated that bio-dielectric fluid produced improved surface characteristics. The surface roughness was observed to reduce. The surface micrograph obtained from scanning electron microscopy also confirms a better surface finish of bio-dielectric fluid over EDM oil. The surface roughness was shown to be most significantly influenced by the discharge current, with the other parameters having little or no effect. The results showed that for bio-dielectric, the lowest Ra was 0.643 µm, and for EDM oil, the highest value of 0.844 µm. The slightest difference in roughness value for two dielectric fluids was 0.013 µm, and the highest difference was 0.115 µm. [ABSTRACT FROM AUTHOR]

This work aims to optimize the machining parameters and study the effect of powder-mixed dielectric fluid on the electrical discharge machining (EDM) process. The TOPSIS method of optimization is adopted to identify the optimal machining parameters. HCHCr die steel is preferred as a machining material. Due to their hard and ductile nature, Ni, Zr, and Ni+Zr were selected as powder inclusion in dielectric fluid. An L9 array Taguchi DOE is preferred to perform the experiments with parameters like peak off time, pulse off time, and pulse current. TOPSIS study revealed that the third level of powder dielectric fluid (Ni+Zr), 7A peak current, 9 µs pulse on time, and 2 µs pulse off time were specified as the optimal condition. Pulse on time (Ton) significantly impacted metal removal rate and surface roughness while machining operation on HCHCr die steel. SEM analysis was done to find the effect of powder-mixed dielectric fluid, while EDAX analysis was done to ensure the presence of powder inclusion. [ABSTRACT FROM AUTHOR]

The problem of a convectional instability in a horizontal dielectric fluid layer with electric field modulation under couple stress fluid is examined. The horizontal dielectric upper boundary fluid layer is cooled, and the lower boundary is subjected to an isothermal boundary condition. The regular perturbation method based on the small magnitude of modulation is used to compute the critical Rayleigh number and the corresponding wavenumber. The solidity of the system is the characterised by a correction Rayleigh number, which is computed as a function of thermal, electric, and couple stress parameters and the frequency of electric field modulation. Some of the known findings are retrieved as specific cases in this study. It is demonstrated that the onset of the convection may be advanced or delayed by the proper regulation of different regulation parameters. The outcomes of this study have potential implications for the control of electroconvection with a time-dependent electric field.

In the manufacturing of power transformers, the impregnation of the solid electric insulation systems (cellulosic materials) with a dielectric liquid is a key issue for increasing the breakdown voltage of the insulation, and this prevents the apparition of partial discharges that deteriorate the insulation system. After introducing the problem, this article presents the theory of impregnation and later carries out a bibliographical review. Traditionally, mineral oils have been used as the dielectric liquid in electrical transformers, but for environmental (low biodegradability) and safety (low ignition temperature) reasons, since the mid-1980s, their substitution with other ester-type fluids has been studied. However, these liquids have some drawbacks, including their higher viscosity (especially at low temperatures). This property, among other aspects, makes the impregnation of cellulosic materials, which is part of the transformer manufacturing process, difficult, and therefore this tends to lengthen the manufacturing times of these machines. [ABSTRACT FROM AUTHOR]

The growing demand for eco-friendly electric vehicles has spurred efforts to extend their driving range, which in turn increases battery heat generation, impacting performance and safety. Immersion cooling technology, known for its superior thermal efficiency, is being extensively researched to overcome the limitations of traditional cooling methods. This study introduces a newly designed metal foam-assisted immersion battery thermal management system (BTMS) and analyzes various BTMS designs incorporating different metal foams and dielectric fluids. This approach aims to enhance cooling performance by effectively utilizing the fluid's capabilities. The metal foam-assisted immersion cooling achieves a maximum temperature of 38.3 °C, which is an improvement over pure immersion cooling at 44.3 °C and conventional cooling at 50.2 °C. Moreover, the temperature difference is reduced from 8 K in conventional methods to 6 K with metal foam. This research evaluates metal foam properties such as porosity, PPI, structure, and material, highlighting the importance of selecting suitable foam. It also investigates various dielectric fluids to determine their impact on cooling performance with and without metal foam. The optimized combination of silver metal foam and fluid configurations achieves a 5 K temperature difference while maintaining energy efficiency, reducing power consumption by 37% with a flow control strategy. The enhanced structure exhibits superior performance at the module level, demonstrating improved fluid uniformity and more effective cooling. • A metal foam assisted immersion cooling system is newly proposed for fast charging. • Metal foam resolves an inadequate utilization of immersion cooling capacity. • BTMSs are comprehensively investigated with various metal foams and fluids. • Silver metal foam with Opteon SF10 exhibits the best battery cooling performance. • Implementation of flow control strategies reduces power consumption by 37%. [ABSTRACT FROM AUTHOR]

The effect of time-periodic electric field modulation on electroconvection in a compactly packed dielectric liquid-permeable layer is investigated using the small perturbation method coupled with the regular perturbation method. The dielectric constant is assumed to be a linear function of temperature. For small amplitude electric field modulation, the critical correction Rayleigh number is determinedusing the regular perturbation method. The critical Rayleigh number is obtained in terms of the electrical Rayleigh number, Vadasz number, normalized porosity, and the modulation frequency to determine the stability of the system. It is found that electric field modulation at low frequencies can create subcritical convective motion. The impact of Vadasz number is shown to be akin to that of the dielectrophoretic force. The stabilizing influence of normalized porosity is more pronounced when the frequency of electric field modulation is modest and large. The study reveals that time-varying electric fields and a densely packed porous layer may have implications for the control of electroconvection in heat transfer applications involving dielectric fluids as working media. [ABSTRACT FROM AUTHOR]

Single-stage electrohydrodynamic (EHD) pumps with electrodes "a diaphragm–a plate with a hole" and "a wire–a plate with a hole" are studied. It is established that the pump characteristics can be significantly improved with the help of flow-limiting diaphragms. It is indicated that it is preferable in the main, multistage EHD pumps to use lattice-type electrodes made of bare and perforated insulated wires. The optimal geometrical parameters of electrodes, flow-limiting diaphragms, dielectric coatings, and interelectrode distances are determined. The influence of the electrophysical properties of the working medium and galvanically isolated high-voltage sources on the performance of a multistage pump is considered. Possible ways to reduce the mutual influence of steps on its output parameters are shown. Formulas have been obtained that accurately reflect the physical nature of the study results for the characteristics of EHD pumps. It was found that organosilicone liquid has the best characteristics, and it is recommended to use it as a coolant in EHD heat exchangers owing to the stability of its properties under the influence of an electric field, microdischarges, and temperature. The reasons for the deterioration of the pump characteristics during its long operation are identified, and the ways to reduce the influence of these factors on the output parameters are described. [ABSTRACT FROM AUTHOR]

This study is centered on the practicality of used cooking oil-based biodiesel (UCOB) as the dielectric for electrical discharge machining (EDM). To establish the usefulness of used cooking oil-based biodiesel as a dielectric for EDM, the essential properties of UCOB were determined and compared with ST EDM oil. Used cooking oil is an important source that can be employed for biodiesel production. Biodiesel was extracted by the process of transesterification. EDM performance was evaluated by applying a “one factor at a time” approach while machining Inconel-625 using EDM oil and bio-dielectric fluids. For both dielectric fluids, the material removal rate was observed to increase with discharge current. The lowest value of TWR was observed at 50 µs while the highest value was observed at 1000 µs. Thus, the performance trend for both fluids was similar. However, the performance of UCOB was slightly better than that of EDM oil. This variation is due to the difference in chemical composition of both dielectric fluids. The highest material removal rate 20.333 mm3/min was observed for UCOB operation at a discharge current of 12.48 A and the lowest material removal rate (0.123 mm3/min) was obtained with a discharge current of 1.56 A for EDM oil. It has been established that UCOB can be suitably utilized as dielectric fluid to increase the sustainability of the EDM process.

This research investigates a tropical indigenous nonedible ester such as Pongamia oil (PO). PO and PO methyl ester (POME) were taken as test samples to develop a nonparametric model for investigations. This work implements the empirical cumulative distribution function (eCDF) to develop a PO and POME lifetime model. The lifetime model of the PO and POME acts as a decisive factor in determining the early failure regions corresponding to the bathtub model. On the other hand, the Bayesian theorem calculates the Bayesian inference. This enables one to foresee the variable as a posterior distribution to conclude their correlation in the parameter space. The developed lifetime model of PO and POME supports experimental results over hypothesis and assists one to predict the risk probability. The model predicted early failures of the PO at less than 40 kV and POME at less than 54 kV and life of POME from 41 to 54 kV and POME at 55–65 kV. The useful life of PO and POME will experience a failure rate of 45% and 25%, respectively. Furthermore, such detections aid power engineers to treat insulating fluids to overcome early aging effects and deterioration of oil–paper insulation. [ABSTRACT FROM AUTHOR]

The results of investigations of electrohydrodynamic (EHD) flows using the schlieren method in the following systems of electrodes are presented: "blade–insulated edge blade," "blade–two rods," and "rod with perforated insulation coating–two rods." Single-stage EHD pumps were designed on the basis of the obtained results. The pressure-flow characteristics of the pumps were studied depending on various factors. It was shown that the performance of the EHD pumps can be increased applying dielectric coatings to the electrodes. The maximum efficiency was obtained in the "blade–blade with insulated edge" system of electrodes, while the maximum static pressure was obtained in a three-rod system with a perforated insulation coating of the emitter. The advantages of a three-rod system were specified as regards to the improvement of the flow characteristics of the pump due to the parallel arrangement of the electrodes and the increase in the pump pressure when using multistage pumps with grid electrodes. [ABSTRACT FROM AUTHOR]

Biodiesel is a chemically modified eco-friendly fuel mainly used as a fuel in compression ignition engines. It is prepared from vegetable oil or animal fat. It is gaining worldwide popularity because it is a renewable, non-toxic, biodegradable, and non-flammable fuel. This paper gives an insight into various aspects of biodiesel. Literature review of biodiesel production, its performance in diesel engine, and the electrical discharge machining process are discussed along with other applications. An innovative biodiesel production plant of 20 L capacity has been designed and developed successfully. The conversion reaction was carried out for 20 L of used cooking oil and 4 L of methanol. The biodiesel production yield of 95.8% was observed for a 1:6 M ratio of methanol and used cooking oil using 200 gm of KOH catalyst at 60 °C for 1 h. In the second phase of the work, a framework for using biodiesel as a dielectric fluid during spark machining is presented. Using biodiesel during the spark machining process can reduce pollution and also enhances the sustainability of the process.

• Lithium titanate oxide batteries are analyzed using the equivalent circuit model. • An effective channeled dielectric fluid immersion cooling system is introduced. • Performance is evaluated considering battery aging and dynamic loading. • The cooling system performs well even at high road gradeability conditions. Lithium titanate oxide is becoming a prominent alternative to graphite as an anode in lithium-ion batteries due to its long cycle life, fast charging/discharging, and ability to function at low ambient temperatures. However, lithium-ion batteries are susceptible to catastrophic thermal runaway under extreme and abusive conditions. The present study proposes a novel channeled dielectric fluid immersion cooling system for the 23Ah lithium titanate oxide batteries modeled using an equivalent circuit model within a multi-scale, multi-domain framework using the commercial solver ANSYS. The novel cooling system reduced maximum temperature and improved temperature uniformity with less immersion fluid requirement than the generic designs. Hydrofluoroether HFE-6120 turned out to be the most effective coolant, and 0.5LPM is the optimum flow rate. When subjected to dynamic loading, the proposed cooling system restricted the maximum temperature to 299.2 K in the aged battery pack with 3972 cycles. Further, the reduced order model is utilized in lieu of the equivalent circuit model to reduce computational time for analyzing the battery pack. Compared to the full-order equivalent circuit model, the reduced order model efficiently captures the battery dynamics with minimal deviations of 1 % and 1.5 % in voltage and temperature, respectively. The computational time is reduced by 26 % with the reduced order model. The proposed cooling system limits the maximum temperature and non-uniformity in the battery pack to 302 K and 1 K under aggressive scaled-down US06 loading conditions with continuous 9° gradeability. This research will be helpful for the future development and understanding of immersion cooling systems for high-energy LTO-based batteries under the impact of aging and gradeability. [ABSTRACT FROM AUTHOR]

In the current scenario, CHF study is essential for the safe operation of electronics equipment comprising a two-phase heat transfer process. Therefore, the present experimental investigation involves saturated pool boiling and CHF study of FC 72 over a plain stainless steel surface (SS) and microporous copper-coated SS surfaces under atmospheric conditions. Accordingly, three different plasma-sprayed copper-coated surfaces with coating thicknesses of 65 μm, 105 μm, and 145 μm prepared using micro copper particles of size 25–45 μm. The analysis of the results shows that with an increase in heat flux values, the boiling heat transfer coefficient increases over plain as well as coated surfaces. The plasma-spayed copper-coated surfaces with a coating thickness of 65 μm and 105 μm exhibit a higher boiling heat transfer coefficient as than the plain surface. On the other hand, a 145 μm thick coated surface resulted in a comparable boiling heat transfer coefficient with the plain SS surface. Among the three porous-coated surfaces, the boiling heat transfer coefficient decreases continuously from 65 μm to 145 μm of the coated surface. On the contrary, to the observed nucleate boiling behavior, all the porous-coated surfaces show a higher value of CHF than the plain surface, and the CHF value is found to increase continuously from 65 μm to 145 μm of the coated surfaces. The enhancement of CHF values was found to be 66.29%, 69.17%, and 77.75% for a coating thickness of 65 μm, 105 μm, and 145 μm, respectively, compared with the plain surface. The porous coating thickness of 65 μm shows a greater value of heat transfer coefficient than 105 μm and 145 μm whereas 145 μm exhibits a higher value of CHF as than 65 μm and 105 μm. [ABSTRACT FROM AUTHOR]

This paper presents a fluidically loaded microstrip patch antenna on a multi-layered substrate with frequency and polarization reconfigurability in the 2400 MHz band. A square patch loaded at all the corners with short circuited λg/4 long stubs is utilized. An arrangement of fluidic channels fabricated by moulding Polydimethylsiloxane (PDMS) with 3D printed mould is incorporated beneath each stub. By injecting or withdrawing distilled water into the channels, variable loads are realized. It exhibits frequency tunable linearly polarized (LP) mode with symmetric loading or circularly polarized (CP) mode with asymmetric loading. The sense of CP can be switched by swapping the loading configuration along the diagonals of the patch. The equivalent circuit for the antenna is presented. A prototype is fabricated and measured. In LP mode, frequency tuning of 7.85% is achieved. The minimum realized gain is 5.67 dBi with cross-polarization (X-pol) isolation 20 dB. In the CP modes, the overlapping bandwidth for |S11| -10 dB and axial ratio 3 dB (ARBW) is 16 MHz for both LHCP/RHCP modes. Frequency tuning of 141 MHz (5.76%) is measured in the RHCP mode. The minimum realized gain is 4.86 dBic and total efficiency is > 60%.

The stability of a horizontal sparsely packed porous layer of a dielectric fluid heated from below is examined when the fluid layer is subjected to time-dependent electric field modulation. The dielectric constant is assumed to be a linear function of temperature. The regular perturbation method is used to find the critical Rayleigh number and the corresponding wavenumber for small amplitude electric field modulation. The stability of the system characterized by a correction Rayleigh number is computed as a function of thermal, electric, and porous parameters, and the frequency of electric field modulation. It is found that the onset of electro-convection can be delayed or advanced by the presence of these parameters. The effect of various parameters is found to be significant for moderate values of the frequency of electric field modulation. Some of the known results are recovered as special cases of the present study. The findings of the present study have possible implications in the control of electro-convection with a time-varying electric field. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this work is to test a battery thermal management system by direct immersion of a commercial 18650 LiFePO4 cell in a low boiling dielectric liquid. It is worth noting that for electric mobility applications, thermal management of Lithium-Ion batteries is a fundamental issue because batteries experience high discharge currents and temperatures. First, we present an electrical characterization of the Lithium-Ion by measuring cell potential, open circuit potential and entropic heat coefficient. Temperature measurements were carried out with thermocouples and infrared thermography. A simplified heat generation term was evaluated using the experimental data. Then, the same battery was immersed in a dielectric low boiling liquid and tested under three different discharge currents. For comparison, also the case without dielectric liquid was analyzed. This paper demonstrates the feasibility of a thermal management system based on direct immersion of a battery cell in a low boiling dielectric fluid. Indeed, the results show a substantial decrease of battery temperature when immersed. [ABSTRACT FROM AUTHOR]

WEDM (Wire electrical discharge machining) is a precision machining method for cutting electrically conductive materials. It is an unconventional machining process that produces precision parts that match the dimensional tolerances of our designs within the range of ±0.0001mm. As the residual stress results in premature failure of parts, the WEDM is preferred for hard to machine materials such as Inconel, Nickel, and other Super alloys. In the present paper, earlier and recent work was reviewed, segregated and evaluated on the effect of wire material, diameter, dielectric fluid, wire wear, pulse on and off times and machining characteristics such as kerf size, machining efficiency, material surface characteristics, etc. This paper also focused on hybrid and ultrasonic-assisted WEDM used for machining of different materials. This paper discussed the major research studies in WEDM.

For the effective use of dielectric sensors, optimization of the design parameters of the sensors, such as the depth of penetration of the electromagnetic fi and the magnitude of the sensor signal, is of great importance. The purpose of the work was to build a mathematical model of a sensor with an open area of space and calculate its parameters.Results of main parameters calculations of the open space sensor are presented. Methods of integral equations and mirror images are used for numerical 2D modeling. The surface of each electrode was considered as two parallel lamellae. This approach simplifi the procedure for numerically solving a two-dimensional problem. It allows you to calculate the electric fi of fl layered media with less time, using less powerful computers. The numerical calculation program is implemented in MAPLE.The program adequacy was checked for a sensor made on one-sided foil Tefl (ε1 = 2,3) with a thickness of b = 1.0 mm. The electric fi was calculated for the sensor in a three-layer medium. The calculated picture of the fi showed that the distribution of force lines is not uniform. It was found that the depth of the control zone does not depend on the metallization of the sensor surface. The depth of the control zone for an open-type sensor is in the same range as the depth of the control zone for fl overhead measuring capacitorsan analog of fringing electric fi d (FEF) sensors.

In the manufacturing of power transformers, the impregnation of the solid electric insulation systems (cellulosic materials) with a dielectric liquid is a key issue for increasing the breakdown voltage of the insulation, and this prevents the apparition of partial discharges that deteriorate the insulation system. After introducing the problem, this article presents the theory of impregnation and later carries out a bibliographical review. Traditionally, mineral oils have been used as the dielectric liquid in electrical transformers, but for environmental (low biodegradability) and safety (low ignition temperature) reasons, since the mid-1980s, their substitution with other ester-type fluids has been studied. However, these liquids have some drawbacks, including their higher viscosity (especially at low temperatures). This property, among other aspects, makes the impregnation of cellulosic materials, which is part of the transformer manufacturing process, difficult, and therefore this tends to lengthen the manufacturing times of these machines.

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)