Thermal Electric Field Research Articles

Generalization on Entropy-Ruled Charge and Energy Transport for Organic Solids and Biomolecular Aggregates.

Herein, a generalized version of the entropy-ruled charge and energy transport mechanism for organic solids and biomolecular aggregates is presented. The effects of thermal disorder and electric field on electronic transport in molecular solids have been quantified by entropy, which eventually varies with respect to the typical disorder (static or dynamic). Based on our previous differential entropy (hs)-driven charge transport method, we explore the nonsteady carrier energy flux principle for soft matter systems from small organic solids to macrobiomolecular aggregates. Through this principle, the synergic nature of charge and energy transport in different organic systems is addressed. In this work, entropy is the key parameter to classify whether the carrier dynamics is in a nonsteady or steady state. Besides that, we also propose the formulation for unifying the hopping and band transport, which provides the relaxation time–hopping rate relation and the relaxation time–effective mass ratio. The calculated disorder drift time (or entropy-weighted carrier drift time) for hole transport in an alkyl-substituted triphenylamine (TPA) molecular device is 9.3 × 10–7 s, which illustrates nuclear dynamics-coupled charge transfer kinetics. The existence of nonequilibrium transport is anticipated while the carrier dynamics is in the nonsteady state, which is further examined from the rate of traversing potential in octupolar molecules. Our entropy-ruled Einstein model connects the adiabatic band and nonadiabatic hopping transport mechanisms. The logarithmic current density at different electric field-assisted site energy differences provides information about the typical transport (whether trap-free diffusion or trap-assisted recombination) in molecular devices, which reflects in the Navamani–Shockley diode equation.

Bioavailability of Rosehip (Rosa canina L.) Infusion Phenolics Prepared by Thermal, Pulsed Electric Field and High Pressure Processing.

In this study, the in vitro bioavailability of rosehip infusion phenolics, mainly catechin, as a response to conventional and non-thermal treatments by combining gastrointestinal digestion and a Caco-2 cell culture model, was investigated. After application of thermal treatment (TT, 85 °C/10 min), high pressure (HPP, 600 MPa/5 min) or pulsed electric field (PEF, 15 kJ/kg) processing, all samples were subjected to simulated gastrointestinal digestion. Then, the amount of maximum non-toxic digest ratio was determined by the cytotoxicity sulforhodamine B (SRB) assay. Next, Caco-2 cells were exposed to 1:5 (v/v) times diluted digests in order to simulate the transepithelial transportation of catechin. Results showed that non-thermally processed samples (5.19 and 4.62% for HPP and PEF, respectively) exhibited greater transportation across the epithelial cell layer compared to than that of the TT-treated sample (3.42%). The present study highlighted that HPP and PEF, as non-thermal treatments at optimized conditions for infusions or beverages, can be utilized in order to enhance the nutritional quality of the final products.

Effect of Hurdle Approaches Using Conventional and Moderate Thermal Processing Technologies for Microbial Inactivation in Fruit and Vegetable Products.

Thermal processing of packaged fruit and vegetable products is targeted at eliminating microbial contaminants (related to spoilage or pathogenicity) and extending shelf life using microbial inactivation or/and by reducing enzymatic activity in the food. The conventional process of thermal processing involves sterilization (canning and retorting) and pasteurization. The parameters used to design the thermal processing regime depend on the time (minutes) required to eliminate a known population of bacteria in a given food matrix under specified conditions. However, due to the effect of thermal exposure on the sensitive nutrients such as vitamins or bioactive compounds present in fruits and vegetables, alternative technologies and their combinations are required to minimize nutrient loss. The novel moderate thermal regimes aim to eliminate bacterial contaminants while retaining nutritional quality. This review focuses on the “thermal” processing regimes for fruit and vegetable products, including conventional sterilization and pasteurization as well as mild to moderate thermal techniques such as pressure-assisted thermal sterilization (PATS), microwave-assisted thermal sterilization (MATS) and pulsed electric field (PEF) in combination with thermal treatment as a hurdle approach or a combined regime.

Path-dependent bifunctional device in thermal-electric field

Janus metamaterial refers to a kind of artificial device that can exhibit different functions along different paths. Compared with the existing metamaterial only possessing the single omnidirectional or unidirectional function, we propose a path-dependent bifunctional device in a thermal-electric field, which can present two distinct thermal and electric behaviors (concentrating and cloaking) under different directions of heat flux and electric current. We theoretically derive the anisotropic material parameters of the ideal Janus device to achieve the path-dependent functionalities based on the successive transformation method. Then, in order to realize the engineering applications of the Janus device, the effective medium theory is employed to eliminate the anisotropy of the material parameters using the multilayered structure, thus avoiding extreme material parameters. We further analyze the path-dependent manipulation effects of the coupled thermal and electric fields. The numerical simulations are carried out to demonstrate the performances of ideal or multilayered Janus devices under different physical conditions. The results show that the performances of the multilayered Janus device coincide with those of the ideal Janus device, and these different Janus devices can perfectly achieve the concentrating function along the x-axis and the cloaking function along the y-axis in different thermal and electric fields simultaneously. It is anticipated that the path-dependent effect of the Janus metamaterial can also be extended to other multi-physical fields with different directional functions.

Design of an omnidirectional camouflage device with anisotropic confocal elliptic geometry in thermal-electric field

SummaryThe designed confocal elliptical core-shell structure can realize the omnidirectional camouflage effect without disturbing temperature and electric potential profiles as the directions of heat flux and electric current change. Based on the anisotropy of the confocal ellipse, the anisotropic effective parameters of the confocal elliptical core-shell structure are derived under different heat flux and electric current launching. Then, the matrix material should be anisotropic as the effective parameters to satisfy the omnidirectional camouflage effect, which is demonstrated numerically. In addition, we present a composite structure to realize the anisotropic matrix. The experimental results show that the camouflage device embedded in the composite structure can eliminate the scattering caused by the elliptical core under different directions of heat flux and electric current, thus achieving the omnidirectional thermal-electric camouflage effect experimentally. The omnidirectional camouflage effect in thermal and electric fields can greatly widen the application fields of this device with anisotropic geometry.

Coupled Electrohydrodynamic and Thermocapillary Instability of Multi-Phase Flows Using an Incompressible Smoothed Particle Hydrodynamics Method

This paper concerns the study of coupled effects of electrohydrodynamic (EHD) and thermocapillary (TC) on the dynamic behaviour of a single liquid droplet. An incompressible Smoothed Particle Hydrodynamic (ISPH) multiphase model is used to simulate EHD-TC driven flows. The complex hydrodynamic interactions are modeled using the continuum surface force (CSF) method, in which the gradient of the interfacial tension and the Marangoni forces are calculated with an approximated error or 0.014% in the calculation of Marangoni force compared to the analytical solutions which is a significant improvement in comparison with previous SPH simulation studies, under the assumption that the thermocapillarity generates sufficiently large stress to allow droplet migration, while the electrohydrodynamic phenomena influences the droplet morphology depending on the electrical and thermal ratios of the droplet and the ambient fluid. This study shows that, when applying a vertical electric field and thermal gradient, the droplet starts to stretch horizontally towards a break-up condition at a high rate of electrical permitivity. The combined effect of thermal gradient and electric field tends to push further the droplet towards the break-up regime. When the thermal gradient and the electric field vector are orthogonal, results show that the droplet deformation would take place more slowly and the Marangoni forces cause the droplet to migrate, while the stretching in the direction of the electric field is not seen to be as strong as in the first case.

Origin of transverse voltages generated by thermal gradients and electric fields in ferrimagnetic-insulator/heavy-metal bilayers

We compare thermal-gradient-driven transverse voltages in ferrimagnetic-insulator/heavy-metal bilayers (Tm3Fe5O12/W and Tm3Fe5O12/Pt) to corresponding electrically-driven transverse resistances at and above room temperature. We find for Tm3Fe5O12/W that the thermal and electrical effects can be explained by a common spin-current detection mechanism, the physics underlying spin Hall magnetoresistance (SMR). However, for Tm3Fe5O12/Pt the ratio of the electrically-driven transverse voltages (planar Hall signal/anomalous Hall signal) is much larger than the ratio of corresponding thermal-gradient signals, a result which is very different from expectations for a SMR-based mechanism alone. We ascribe this difference to a proximity-induced magnetic layer at the Tm3Fe5O12/Pt interface.

Electroosmotic modulated unsteady squeezing flow with temperature-dependent thermal conductivity, electric and magnetic field effects

Modern lubrication systems are increasingly deploying smart (functional) materials. These respond to various external stimuli including electrical and magnetic fields, acoustics, light etc. Motivated by such developments, in the present article unsteady electro-magnetohydrodynamics squeezing flow and heat transfer in a smart ionic viscous fluid intercalated between parallel plates with zeta potential effects is examined. The proposed mathematical model of problem is formulated as a system of partial differential equations (continuity, momenta and energy). Viscous dissipation and variable thermal conductivity effects are included. Axial electrical distribution is also addressed. The governing equations are converted into ordinary differential equations via similarity transformations and then solved numerically with MATLAB software. The transport phenomena are scrutinized for both when the plates move apart or when they approach each other. Also, the impact of different parameters such squeezing number, variable thermal conductivity parameter, Prandtl number, Hartmann number, Eckert number, zeta potential parameter, electric field parameter and electroosmosis parameter on the axial velocity and fluid temperature are analysed. For varied intensities of applied plate motion, the electro-viscous effects derived from electric double-capacity flow field distortions are thoroughly studied. It has been shown that the results from the current model differ significantly from those achieved by using a standard Poisson–Boltzmann equation model. Axial velocity acceleration is induced with negative squeeze number (plates approaching, S < 0) in comparison to that of positive squeeze number (plates separating, S > 0). Velocity enhances with increasing electroosmosis parameter and zeta potential parameter. With rising values of zeta potential and electroosmosis parameter, there is a decrease in temperatures for U e > 0 for both approaching i.e. squeezing plates (S < 0) and separating (S > 0) cases. The simulations provide novel insights into smart squeezing lubrication with thermal effects and also a solid benchmark for further computational fluid dynamics investigations.

Thermal and pulsed electric field (PEF) assisted hydration of common beans

Hydration, a crucial preliminary stage of dried bean processing is mostly performed as a slow, batch-wise process. Here we investigated the effect of thermal and pulsed electric field (PEF)-assisted hydration of two common beans (Phaseolus vulgaris) on hydration behaviour, mass loss and leaching of bioactive components. Beans were hydrated in media either using a thermal process (30–80 °C, 10 °C intervals) until equilibrium moisture content (EMC) was reached or were hydrated to 40 g/100 g dry basis moisture at 45 °C, then PEF-treated at an electric field intensity of 4 kV/cm, f = 2 Hz, pulse width 15 μs, pulse numbers from 200 to 1000 (specific energy from 91 kJ/kg to 455 kJ/kg) and further hydrated until EMC. PEF-assisted hydration reached higher equilibrium moisture values and reduced the hydration time by 3-fold for small red beans (1000 pulses, 455 kJ/kg specific energy) compared to 45 °C soak, however, it also leached higher amounts of bioactive polyphenols into the media. Comparable losses of prebiotic oligosaccharides from beans into the media were found in the two hydration approaches. PEF-assisted hydration is a promising alternative to soaking to reduce process time for slow hydrating beans and leaching of bioactive components could be minimised through process optimization.

Bifunctions of invisible sensors and cloaks in thermal–electric fields

The thermal–electric bifunctional devices with isotropic and anisotropic geometries are designed in this paper, which can realize different control functions (invisible sensors and cloaks) of thermal and electric fields. We first theoretically achieve the bifunctions of invisible sensors and cloaks with isotropic and anisotropic geometries. When the material parameters of the core and matrix and the geometric parameters of the core, inner shell, and outer shell are determined, the thermal–electric invisible sensors could be realized. Meanwhile, the invisible sensors will degrade to invisible cloaks as the inner shell material is insulating. The simulations applying the derived material parameters have also been conducted to verify the thermal–electric bifunctions of different circular and confocal elliptical devices. The results show that the thermal–electric bifunctional devices can effectively control the thermal and electric fields, and these devices exhibit perfect performance of the thermal–electric functions of invisible sensors and cloaks. This work presents a new method to realize thermal–electric bifunctional devices and opens a new window to the development of multi-physics field.

Enhanced tunneling distance of near field radiative energy with high-index dielectric resonators

By placing high-index dielectric resonators on surfaces supporting surface plasmons in the near field, strong magnetic resonance can be observed in the high-index dielectric resonators with appropriate heights around the surface plasmon resonance frequencies. The strong magnetic resonance allows strong thermal photon tunneling across a 1 μm gap, which is one order longer than the previous demonstrations of near field radiation with surface plasmons. The thermal photon tunneling happens when the horizontal wavenumber is kx∼4πw with w is the width of the high-index resonators. The height of the high-index dielectric resonators should provide enough retardation of the electric field between the top and bottom of the resonator to form a displacement current loop. Therefore, similar magnetic field resonance occurs in the resonator when we triple rather than double the height of the high-index dielectric resonators. The usage of dielectric resonators to amplify the thermal electric field in the near field domain can be a potential method to increase the quasi-monochromatic radiation distance of an emission domain by one order or more at the frequencies of the surface waves.

Comparison of different fluid-thermal-electric multiphysics modeling approaches for thermoelectric generator systems

This work proposes a novel fluid-thermal-electric multiphysics numerical model to predict the performance of thermoelectric generator systems applied to fluid waste heat recovery, with the consideration of multiphysics coupling effects of fluid, thermal, and electric fields. The comprehensive numerical simulations of the thermoelectric generator system are performed via COMSOL coupled solver. Besides, the effect of the neglect of parasitic heat on the output performance is investigated through the comparison with numerical results predicted by ANSYS and COMSOL separate solver, wherein the fluid-thermal field is computed first, then the thermal-electric field. The results show that the output power predicted by COMSOL separate solver is 8.52% lower than that predicted by COMSOL coupled solver at the inlet air temperature of 550 K and inlet air velocity of 30 m/s due to the neglect of parasitic heat. The output performance of the TEG system predicted by ANSYS is less affected by inlet air boundary conditions than that predicted by COMSOL. Finally, the experimental results show that the fluid-thermal-electric multiphysics model solved by the COMSOL coupled solver shows the lowest output power deviation of 2.81%. The proposed model can guide the numerical modeling of the thermoelectric generator system applied to fluid waste heat recovery.

Application of Emerging Cell Disintegration Techniques for the Accelerated Recovery of Curcuminoids from Curcuma longa

Curcuminoids, the bioactive compounds with many beneficial effects on human health, exist in Curcuma longa (turmeric). In the present study, the impact of different cell disintegration techniques to enhance total curcuminoid recovery (TC) from fresh and dried turmeric was investigated. The impact of thermal pretreatment (TP), ultrasound pretreatment (UP), enzyme pretreatment (EP), and pulsed electric field pretreatment (PEF) on the recovery of curcumin (CUR), demethoxycurcumin (DMC), and bis-demethoxycurcumin (BDMC) from fresh and dried turmeric were studied. The cell disintegration index (Zp) and high-performance liquid chromatography (HPLC) analysis of curcuminoids were performed to evaluate the efficiency of the applied techniques. With fresh turmeric, the highest curcuminoid recovery was 83.6 mg/g dry basis with EP. The highest structural tissue damage was obtained with UP achieving a cell disintegration level of 92.5%. The technology with the highest time-saving and low specific energy input was PEF with a total curcuminoid recovery of 80.9 mg/g dry basis. Working with dried turmeric, the drying required high specific energy input for 72 h at 50 °C; however, the untreated dried sample reached 125.3 mg/g dry basis of TC without further pretreatment after drying.

Realization and analysis of an Intelligent flux transfer regulator by allocating thermal and DC electric fields

Flexible regulation of fluxes means a lot due to its enormous potential for efficient utilization of various energy sources. Benefitting from the emerging transformation optics-based technology and metamaterials, regulation structures manipulating different energy fluxes have aroused wide attention, relevant research have progressed rapidly in recent years. However, many studies are suffering from over-complicated problem and confined to a single function or a single available occasion. Hence, design of flux regulation device requires improvement to ease the processing burden, and functional diversity as well as application scope need in-depth development to meet requirements for more sophisticated practical settings. Furthermore, appropriate evaluation index for comprehensive assessment of energy transportation procedure should never be ignored. Here, we design an intelligent flux transfer regulator that can actively switch between concentration and rotation states based on temperature change by allocating thermal and DC electric fields. Improved geometric and conduction parameters are selected to avoid non-uniform distribution problem. Counting on the diffusivity of the implicated thermal field, the local entropy generation rate as a thermodynamic indicator is introduced to evaluate energy quality during state-switch process in transient mode. Influences of different design variables on control effect as well as energy fluctuation are also studied. Combing discretization method, effective medium theory, spiral bimetal sheet and other control setups, we experimentally confirm the effectiveness of the proposed device. Our work enriches the practicability and application of regulation device for energy control and utilization, opens an avenue for investigating energy transportation phenomena from the perspective of different disciplines.

Visualizing structural changes of egg avidin to thermal and electric field stresses by molecular dynamics simulation

Eggs are one of the most common ingredients used by human beings due to their nutritional attributes and health benefits. However, eggs also contain an anti-nutrient known as avidin, which forms an avidin-biotin complex, resulting in biotin unavailable in the body for absorption. In the present study, molecular dynamics (MD) simulation was used to evaluate the effect of external stresses, including thermal and oscillating electric field (0.05 V/nm, 2450 MHz) at 300–353 K on the structural properties of avidin. The modeling was performed using a GROningen MAchine for Chemical Simulations (GROMACS) software. The alteration in conformation of avidin was evaluated in terms of the number of hydrogen bonds, root mean square deviation, the radius of gyration, and solvent accessible surface area. The application of thermal stress and electric field resulted in conformational changes in the avidin protein. The results also showed that hydrogen bonds have a significant influence on the stability of alpha-helices, which are responsible for the compactness of the molecule. Change in the hydrogen bonds can increase the surface area and hence the surface properties of avidin significantly. Thermal combined with electric field showed an application in inhibiting the activity of avidin present in egg white.

Effect of pulsed electric field processing on reduction of sulfamethazine residue content in milk.

The whole milk spiked with sulfamethazine was treated under thermal and pulsed electric field processing for maximum reduction. The low-temperature long-time (LTLT, 62.5°C for 30min), high-temperature short time (HTST, 72°C for 15 s) pasteurization and ultra-high temperature processing (UHT, 138°C for 2 s) resulted in the reduction of sulfamethazine 7.3, 5.2 and 4.6% respectively. PEF and combination treatment (thermal + PEF) were found to reduce sulfamethazine content in milk by 67-72% and 73-76% respectively. Combined treatment of milk resulted in a higher percentage of reduction. Similar predicted and actual values proved that they fit the linear regression model and successful application of pulsed electric field technology in reducing antibiotic residues. PEF and mild thermal treatment can be a promising technology to reduce the antibiotic residues with ensuring minimal negative impact on the nutritional quality of food.

Impact of pulsed electric field processing on reduction of benzylpenicillin residue in milk.

The presence of residues of veterinary drugs in animal-derived food is one of the major problems for food safety. The consumption of milk containing antibiotic residues can evoke allergic reactions in hypersensitive individuals, disorders of intestinal flora and produces the risk of emerging antibiotic resistance microorganism. In this study, the effect of the thermal treatments and pulsed electric field (PEF) on the reduction of benzylpenicillin (PNG) spiked artificially in milk was evaluated quantitatively by calculating the loss of the concentration using HPLC. Fresh raw milk was subjected to a high-temperature short-time (72°C for 15s, HTST), low-temperature long- time (62.5°C for 30min, LTLT) and ultrahigh-temperature processing (138°C for 2s, UHT). The PEF process factors output voltage (20-65%) and pulse width (10-26μs) were optimized for maximum reduction of PNG by employing the statistical tool response surface methodology (RSM). HTST, LTLT, and UHT have resulted in the reduction of PNG 13.5%, 6.1%, 1.2% respectively. The optimized parameters of the PEF treatment had reduction efficiency in the range of 79-86%. The saddle response surface obtained from RSM showed that the center was neither at maximum point nor at the minimum point. The predicted and experimental values of the response were nearly similar which proved the suitability of the fitted quadratic model. Combined thermal and PEF treatment has a significant synergistic effect in reducing the PNG. PEF induced reduction efficiency achieved was 79-86%. The reduction percentages were observed higher in the combined pasteurization and PEF treatment of milk. The pulsed electric field can be adopted as a unique processing tool for degradation of antibiotic residues whilst retaining nutritional quality parameters.

Drying technologies for edible insects and their derived ingredients

Edible insects and their ingredients are considered as a novel, sustainable and high-quality nutritional source for their potential use as food and feed. However, they are highly oxidizable and potentially unsafe. Dehydration of insects removes moisture and extends their shelf life. Moreover, it is considered as a prerequisite and/or pretreatment for some extraction technologies for ingredient production. Drying technologies (sun drying, smoke drying, roasting, freeze drying and oven drying) have been used to dry insects, both at a laboratory and industrial level. Different drying pretreatments (thermal blanching, microwave-assisted drying and pulsed electric field) have been explored to improve the final quality of the insect products, extending their shelf life and reducing total energy consumption. Therefore, this article aimed to review the current research available in edible insect drying processing technologies, addressing their effectiveness and their influence over different quality parameters such as protein/lipid extraction efficiency, sensory characteristics of the final products, microbiological safety, shelf life and their impact on bioactive compounds.

Optical nonlinear, EPR, second harmonic generation and Faraday rotation studies on diamagnetic solid: Influence of thermal poling

The electric field manipulation of magnetic and magneto optical properties is currently of great interest for photonics and spintronics devices. In this study, for the first time, we utilized the thermal poling electric field induced polarization and magnetization to manipulate the magnetic and Faraday rotation performance of heavy metal oxide diamagnetic glass. The influence of poling conditions on second & third nonlinearity, structure and defects, thermal, magnetic and magneto optical properties were studied through varies characterization techniques such as scanning electron microscope, X-ray powder diffraction, Raman, maker fringe, electron paramagnetic resonance, X-ray photoelectron spectroscopy, Z-scan, vibration sample magnetometer and Faraday rotation measurements. 5 µm-thickness layer second harmonic generation intensity increased with the voltages from 1 kV to 3 kV, while at 300°C second harmonic generation the intensity decreased. Third nonlinearity coefficient and nonlinear refractive index were calculated to be much higher than that of un-poled glass through the Z-scan method. X-ray photoelectron spectroscopy, Raman and electron paramagnetic resonance analysis revealed the center-asymmetric network of glass, non-bridging oxygen and defect centers after thermal poling. The modification on glass structure resulted in the enhancement of magnetic moment of glass with electric induced magnetic field changes electric coupling effect as high as 15%. Faraday rotation measurement indicated that polarization dominantly contributed to the enhancement of V, at the same time, the V also was impacted by glass transmittance and crystal scattering. The optimized thermal poling condition was determined to be 3 kVand 260°C for 4 hours, under which thermally poled glass presented the strong second harmonic generation intensity (2.3 pm/V), highest Verdet constant (0.2382 min/G.cm) and improved diamagnetic susceptibility (0.424×10−5 emu/mol). Diamagnetic glass with these properties is attractive for magneto optical sensing and nonlinear applications.

High Temperature Insulation Materials for DC Cable Insulation — Part I: Space Charge and Conduction

Fundamental studies of potential candidates for DC electric power transmission in high temperature environment, including ETFE, FEP, PTFE, PI and PEEK, are carried out and presented in form of the series papers containing space charge and conduction as part I, partial discharge as part II, and the degradation and surface breakdown as part III. In this part, the space charge at 20kV/mm was measured at 25 °C and with a thermal gradient at 50 °C. The electrical conductivity was measured at electric fields ranging from 10kV/mm to 30kV/mm in temperatures ranging from 25 °C to 200 °C. The experimental results showed that considering the effect of thermal condition and electric field, FEP has the lowest total amount of space charge accumulation and electric field distortion among these materials at the measured conditions. PI and PEEK have the lowest amount of trap-controlled mobility at 25 °C due to deeper average trap level because of the aromatic rings in the structure. PTFE and PI have the lowest amount of thermal activation energy and temperature-dependent electrical conductivity due to the more uniform morphological phase comparing to ETFE, FEP, and PEEK. The outcomes of this paper serve as a benchmark for the fundamental researches over high temperature materials for DC applications and lay a basis for Part II and Part III.