Gas-solid phase equilibrium under the influence of an electric field is a key area of technological innovation research in fields such as chemical engineering, catalysis and electric field-controlled refrigeration. However, research on this phenomenon remains hampered by the ambiguous multi-physics coupling mechanisms, the scarcity of experimental data, and the excessive complexity of theoretical models. Based on phase equilibrium theory and the chemical potential in an electrostatic field, this study elucidates the interplay between pressure, temperature, and permittivity during gas-solid phase transitions. A gas-solid phase equilibrium equation under the influence of an electrostatic field was established, in the absence of an electric field, this equation reduces to the classical Clapeyron equation. Based on the derived gas-solid phase equilibrium equation, the pressure and temperature control parameter of an electrostatic field on the sublimation of water vapor, naphthalene, and croconic acid were calculated. The results show that the electrostatic field induces a negative pressure control parameter or a positive temperature control parameter for water vapor, whilst it yields a negative temperature control parameter for croconic acid; the effect on naphthalene is weak. These theoretical predictions are consistent with experimental findings in the literature. Physically, a negative temperature control parameter (or positive pressure control parameter) occurs when the field-induced chemical potential change in the vapor phase surpasses that in the solid phase; conversely, the opposite trend is observed when the solid-phase response dominates.

Herein, the phosphorylated FeSiB@Fe3O4 amorphous soft magnetic composites (ASMCs) were designed and fabricated via powder metallurgy technology using high-temperature thermal decomposition. The influence of Fe3O4 content on the microstructure, interface, and electromagnetic properties of phosphorylated FeSiB ASMCs was systematically investigated. Uniformly distributed Fe3O4 magnetic nanoparticles (17.9 nm average size) with high saturation magnetization and low coercivity were synthesized, effectively filling powder gaps and enhancing resistivity from 0.585 S2 m to 1.187 S2 m, which mitigates magnetic dilution and reduces eddy current losses. Three-dimensional loss separation analysis confirms optimal Fe3O4 addition decreases hysteresis, eddy current, and excess losses. However, excessive Fe3O4 causes severe agglomeration, significantly increasing hysteresis loss. As a result, the phosphorylated FeSiB@Fe3O4 ASMCs with 0.2 wt% Fe3O4 nanoparticles achieve the lowest core loss of 118 kW/m3 (at 100 kHz/50 mT) and high effective permeability of 65. This work provides a novel approach for designing high performance and ultralow loss SMCs for high frequency applications.

The SiO2 insulating layer was prepared on the FeSiCr powders successfully by one-step dumping sol-gel method and ammonia was used as the catalyst. It is found that the growth of SiO2 layer can be tuned by the ammonia concentration. Within the reaction time of 0.5 h, SiO2 grows with heterogeneous nucleation when the ammonia concentration is 0.08-0.16 ml/g, and SiO2 coating layer was relatively uniform. With a high ammonia con-centration of 0.20-0.24 ml/g, SiO2 grows with both heterogeneous and homogeneous nucleation, and SiO2 particles gathered and grew. The saturation magnetization and effective permeability of FeSiCr@SiO2 SMCs gradually decrease with the increase of ammonia concentration, while the specific resistance, quality factor and DC-bias property increase. With the ammonia concentration of 0.12 ml/g, the thickness of SiO2 insulating layer was about 30-60 nm. The annealed FeSiCr@SiO2 soft magnetic composite shows good soft magnetic perfor-mance with effective permeability and core loss of 45.52 and 418.32 kW/m3 at 0.05 T and 100 kHz, respectively, and the quality factor of 76.5 at 1 MHz.

液滴的凝结与蒸发是一种相变过程,它既是一种高效的传热传质过程,又与环境气候变化密切相关.实验表明,静电场对液滴的形成过程有重要的影响,是一种有效的强化传热传质方式,也与雷电雨的形成有关.本文基于相平衡理论,利用电场作用下的热力学方程导出了静电场作用下球形介电液滴内外的压强差、蒸气压以及液滴平衡半径的数学表达式.采用数值计算的方法,利用该数学表达式对液滴的形成过程进行了分析.结果表明,与没有电场作用相比,静电场作用下介电液滴内外的压强差、蒸气压以及平衡半径都有增加.蒸气压和平衡半径增加将加速液滴的蒸发过程,因此静电场作用能够促使液滴的快速蒸发.该结论与实验相符,可为相关的理论研究及工程应用提供参考.

Previous studies showed that electric fields could change the boiling point and vapor pressure of the vapor–liquid equilibrium (VLE) state of pure substances and mixtures. This is an important feature in controlling the separation of mixtures. In this paper, based on the principle of phase equilibrium, together with the formulas of chemical potential including the effect of electric field and the dielectric pressure, the Raoult’s law was extended to include the effect of electric field to describe VLE of a mixture under an external electric field. The effects of electric field on VLE can be calculated by combining the extended Raoult’s law and the Dalton’s law of partial pressure, and then, the effect of electric field on the relative volatility can also be calculated. Numerical calculations showed that the effects of an electric field on VLE depend on both the magnitude and the direction of the electric field, and the effects become obvious until the field strength is greater than 10 ^7 V/m. When the direction of the electric field is parallel to the gas–liquid interface, the vapor pressure decreases; the equilibrium temperature, the mole fractions of the volatile component, and the relative volatility increase. While, when the direction of the electric field is perpendicular to the gas–liquid interface, the opposite changes in these properties appear. The shifting of the equilibrium curves caused by the electric field indicates that the electric field can cause the vapor–liquid phase transition and change the amount of the phase material.

FeSiCr soft magnetic composites (SMCs) were fabricated by the sol-gel method, and an Al2O3/resin composite layer was employed as the insulation coating. By the decomposition of boehmite (AlOOH) gel into Al2O3 in the temperature range of 606–707 °C, a uniform Al2O3 layer could be formed on the FeSiCr powder surface. The Al2O3 insulation coating not only effectively reduced the core loss, increased the resistivity, and improved the quality factor, but it also increased the thermal conductivity of SMCs. The best overall properties with saturation magnetization Ms = 188 emu/g, effective permeability μe = 39, resistivity ρ = 8.28 × 105 Ω·cm, quality factor Q = 94 at 1 MHz, and core loss = 1173 mW/cm3 at 200 kHz and 50 mT were obtained when the SMC was prepared with powders coated by 0.5 wt.% Al2O3 and resin. The optimized SMC exhibited the lowest core loss with 27% reduction compared to the resin only-insulated sample and 71% reduction compared to the sample without insulation treatment. Importantly, the thermal conductivity of the SMCs is 5.3 W/m·K at room temperature, which is higher than that of the samples prepared by phosphating and SiO2 coating owing to the presence of a high thermal conductive Al2O3 layer. The high thermal conductivity is beneficial to enhancing the high temperature performance, lifetime, and reliability of SMCs. This work is expected to be a valuable reference for the design and fabrication of SMCs to be applied in high-temperature and high-frequency environments.

In this work, FeSiCr powders were coated with a SiO2 insulation layer for soft magnetic composites (SMCs) through elemental silicon powder hydrolysis, without using any expensive precursors. The effects of the reaction temperature and ammonia concentration on the structure and performance of SMCs were investigated. Through the elemental silicon powder hydrolysis process, the formation of an FeSiCr–SiO2 core-shell structure effectively reduced the core loss, increased resistivity, and improved the quality factor of SMCs. SMCs prepared with 0.10 mL/g ammonia concentration at 50 °C exhibited the best combination of properties, with saturation magnetization Ms = 169.40 emu/g, effective permeability μe = 40.46, resistivity ρ = 7.1 × 106 Ω·cm, quality factor Q = 57.07 at 1 MHz, and core loss Ps = 493.3 kW/m3 at 50 mT/100 kHz. Compared to the uncoated sample, SMCs with a SiO2 coating exhibit 23% reduction in Ps, with only 6.6% reduction in μe. Compared to SMCs fabricated using the traditional sol-gel method, the sample prepared through hydrolysis of elemental silicon powder has higher permeability and lower core loss. In particular, this new approach gives an effective coat solution for the mass production of high-temperature-resistant SMCs.

Fe-based amorphous powder cores (AMPCs) were prepared from FeSiBCr amorphous powders with phosphate–resin hybrid coating. The high-frequency magnetic properties of AMPCs annealed at different temperatures were systematically studied. After annealing at low temperatures, the effective permeability and core loss improved due to the internal stress of the powder cores being released. The sample annealed at 480 °C exhibits the lowest hysteresis loss of about 29.6 mW/cm3 at 800 kHz as well as a maximum effective permeability of 36.4, remaining stable until 3 MHz, which could be useful for high-frequency applications.

电场作用能够较明显地改变电介质系统的物理性质,相关的研究和应用越来越受到广泛的关注.本文以平行板电容器置于一个单相流体电介质系统为模型,详细地探讨了均匀静电场对流体电介质系统的压强和摩尔分数的作用效果.基于相平衡的基本原理,利用电场作用下化学势的表达式,导出了气体和液体电介质系统的压强和摩尔分数随电场强度的变化规律.结果表明:压强和摩尔分数的变化与电场强度的平方成正比,还与温度及电介质的摩尔质量、密度和介电常数有关.静电场作用可以使系统的压强上升,也可以改变混合物的摩尔分数,但组分的摩尔分数是增加或减小决定于组分的摩尔质量和密度的相对大小.静电场作用下,液体的变化大于气体的变化.本文的研究成果为测量介电常数、气体的富集和混合液体的组分调控提供了一种新的思路.

With the aim to meet customers diverse energy needs by an economical and ecological means, integrated energy system has become a popular choice. Amongst various integrated energy system coupling configurations, individual heating infrastructure entails painstaking attention due to rapid expansion. Individual heating network plays a massive role in carbonizing the atmosphere as traditionally individual heating demands are fulfilled by fossil fuel-fired (natural gas and coal) boilers. Recently, trend is heading towards the integration of energy efficient technologies like micro combined heat and power and heat pumps to replace fossil fuel boilers. However, individual heating performance evaluation is generally investigated by energy analysis that employs only the first law of thermodynamics, thereby exergy analysis assessment and its comparison with energy analysis become noteworthy to measure actual performance. In this work, energy and exergy analysis of the individual heating network of China for the year 2030 is performed under the framework of both laws of thermodynamics. The proposed work includes various technological options like Hydrogen fired micro combined heat and power, natural gas fired micro combined heat and power and heat pumps to replace the fossil fuel boilers intending to attain an economically viable and carbon-free environment. At first, energy and exergy efficiencies of the aforementioned heat producing components are computed and afterwards EnergyPLAN technical simulation strategy is employed to evaluate performance in terms of costs, CO2 emissions and primary energy supply. Subsequently, a comparison of both analysis is provided in order to present the difference between the two analysis which substantiates that exergy analysis provides inferior results than energy analysis as depicted in case 3 where heat pumps inclusion appears to be the most decarbonized alternative for energy analysis but corroborates vice versa for exergy analysis. However, exergy analysis complements the energy analysis that helps evaluating the actual performance of system in relation to climate change mitigation and cost-effectiveness.

Sustainable, inexhaustible, economical, and clean energy has become a vital prerequisite to replace fossil fuel sources for power production. In such a context, countries like Pakistan, which are heavily skewed towards fossil fuel-fired plants, are diverting attention to install more and more indigenous renewable energy sources projects such as solar-photovoltaic and wind turbine power plants. In order to harness the maximum energy of wind turbines, it is crucial to factually and precisely assess system performance, which is traditionally inferred by energy analysis (first law analysis). Nevertheless, this analysis only computes the nominal power generation output and ignores the effect of meteorological variables that can lead to some serious errors during the energy planning phase. Consequently, this case study presents both the energy and exergy analysis of a wind farm located in Gharo town of Thatta District along the coastline of the Indus Delta. Energy analysis is carried out to quantify energy efficiency, while exergy analysis computes exergy efficiency by taking into account the effect of pressure, temperature, and wind speed. Comparisons of both efficiencies are provided, and the result substantiates that exergy efficiency turns out to be lower than energy efficiency. However, exergy is a more viable index due to the inclusion of exergy destruction, and in comparison to the energy indicator, it presents the actual performance of a thermodynamic system. The monthly energy and exergy efficiency of the general electric wind turbines are maximum in July having values of 0.5 and 0.41, respectively.

Efficient energy deployment, fossil fuel sources reduction and Intermittent Renewable Energy Sources (IRES) integration has become a core goal of power system operators to attain sustainable and environmentally benign energy system. In such context, Integrated Energy System (IES) is a promising solution to improve system performance by coupling various energy carriers in an energy hub to fulfill diverse consumers’ energy needs. However, the widely used criteria for energy system modelling is based on energy analysis that considers energy quantity only and neglects energy quality. Consequently, exergy index computation becomes a vital issue that accounts energy quantity along with energy quality to provide an accurate assessment. Hence, this paper proposes an exergy hub approach to model IES that constitutes electricity, District Heating (DH) and Individual Heating (IH) infrastructure of China for the year 2020. At first, the exergy efficiency of energy-producing components is calculated by using Cycle-Tempo and Engineering Equation Solver (EES). Then, IES performance is evaluated by computing annual costs, Primary Energy Supply (PES), CO2 emissions and renewable energy share with the help of EnergyPLAN technical simulation strategy. These aforementioned performance indicators are investigated for three different cases like IRES maximum integration in electricity infrastructure (Case 1), Heat Pump (HP) inclusion in IH infrastructure (Case 2) and Thermal Storage (TS) addition in DH infrastructure (Case 3) and these cases comparison with energy hub results are also provided. Energy and exergy hub approaches substantiate different results as IRES integration proves the most cost-efficient and decarbonized alternative in exergy hub while in energy hub TS addition is the best case alternative. Though IRES integration deemed cost-efficient with reduced emissions in exergy hub but in comparison to energy hub, this case is costly as exergy efficiency of IRES are lower than energy efficiency. Similarly, HP and TS exergetic results are inferior to energetic because high quality energy is being exploited to produce low quality energy and heat producing components are less exergetically efficient.

碳纳米管是一种应用非常广泛的电磁材料,研究其复介电常数的计算不仅能了解其介电性能规律,而且对材料的设计具有重要意义.基于碳纳米管的等效传输线模型,建立了微波场作用下多壁碳纳米管管壁间电容和量子电容的联接模型,推导了多壁碳纳米管等效传输线的阻抗公式.基于复电导率与复合材料阻容网络模型,建立了多壁碳纳米管复合材料复介电常数的计算公式.根据所得结论,模拟计算了2～18 GHz频率下,管长为20μm、管外径分别为25、40、70 nm的碳纳米管复合材料的相对复介电常数,以及管外径为20 nm,管长分别为60、100μm、厚度为4 mm的碳纳米管复合涂层的微波反射损耗,结果与文献实验值能较好吻合;计算结果也表明,随碳纳米管管径、管长增大,其相对复介电常数的虚部均增大,而且管长对相对复介电常数的影响明显大于管径.

Microwave-assisted extraction is a new effective method which has practical applications in many fields. Microwave heating is one of its physical mechanisms, and it also has the characteristic of selectivity. When the applied microwave frequency equals a certain absorption frequency of the material (or specific component), the material will intensively absorb microwave energy. This is also known as resonant absorption, and the frequency is called the peak absorption frequency which depends on the physical structure of the material. In this work, dynamic hydrogen bond energy was included in molecular activation energy; with the liquid cell model, the expression of interaction energy between dipolar molecules was derived. The rotational relaxation time was gotten from the Eyring viscosity formula. Then based on the relationship between dielectric dissipation coefficient and relaxation time, the expression of microwave peak absorption frequency as a function of the material physical structure, rotational inertia and electrical dipole moment of molecules was established. These theoretical formulas were applied to water and benzene, and the calculated results agree fairly well with the experimental data. This work can not only deepen the study of the interaction between microwave and material, but also provide a possible guide for the experiment of microwave-assisted extraction.

Vapor pressure and boiling point are important thermodynamic properties of vapor–liquid equilibrium (VLE). Experiments showed that the electrostatic field can shift the VLE, and thus it is desirable to understand this physical mechanism for applications. Applying the expression of electrohydrodynamic (EHD) force on the phase interface, an expression of dielectric pressure caused by the presence of electrostatic field is derived, which is sensitive to the direction of the electric field. An expression of chemical potential including the influence of electrostatic field was derived from the fundamental thermodynamic equations and the definition of chemical potential. Then, based on the principle of phase equilibrium, Kelvin equation was extended to include the effect of the electrostatic field. Finally, an expression of vapor pressure with the influence of the electrostatic field was derived by a combination of the dielectric pressure and the extended Kelvin equation, which is also the relation between vapor pressure and boiling point under the action of the electric field. The characteristics of the vapor pressure were discussed, and an improved novel heat transfer device was proposed.

能量在传递和转化过程中是守恒的,但不同形式的(炯)在传递和转化过程中有不同程度的损耗,对该过程的深入理解有助于合理而又高效地利用能源.任何形式的能和(炯)都可以被表示为一对基本强度量和基本广延量的乘积.利用基本强度量乘以与其共轭的基本广延量的平衡方程,导出了(炯)传递和转化的普遍化动力学方程.该普遍化动力学方程表示出了任意形式的(炯)在传递过程中与其它形式的(炯)之间的转化关系,由此导出了在工程领域常见的动(炯)、化学(炯)、压(炯)、电(炯)和热(炯)的传递和转化动力学关系式,并给出了系统总(炯)的表述式.这些动力学关系式不仅清楚地反映了系统内部不同形式(炯)之间存在的相互转化关系,而且还定量地反映了各种转化过程的不可逆性.

基于一种利用热水和电能联合给3个空间加热的模型,建立与之相应的能量网络,利用广义基尔霍夫定律建立能量网络方程,求解该方程得到能量网络中所有支路的工作状态.每增加一个加热空间,能量网络方程增加4个变量(2个强度量和2个广延量);相应增加2个强度量方程和由热负荷提供的2个约束条件,方程组封闭可解,表明建立的能量网络方程可推广到具有任意数量热负荷的能量网络.利用一组典型的数据计算3个热负荷能量网络中各设备的工作状态,结果与利用电网络和流体网络计算的结果相同,表明建立的能量网络方程及其求解方法可靠.本研究可为综合能源系统的分析和优化提供理论指导.

The effects of secondary particle size distribution on the electromagnetic properties of the carbonyl iron powder cores have been investigated in this work. For preparing the cores, the iron powders were firstly undergone insulation treatments including phosphorization and organic coating. After granulation, the secondary particles with different size distributions were molded into the final shape and cured at 200 degrees C. The results show that for the secondary particles with unimodal size distribution, the real part of the complex magnetic permeability of the powder core is in inverse proportion to the particle size. For the cores prepared from the secondary particles with bimodal size distribution, the effects of the size ratio and volume ratio of the coarse particle/fine particle on the magnetic properties are discussed. It is found that the permeability increases with the increasing volume of fine secondary particles. The minimum magnetic loss factor value is obtained at the coarse/fine secondary particles volume ratio of 7:3. The density and magnetic properties including complex permeability and magnetic loss of the cores prepared with coarse/fine particles size ratio of similar to 3 and similar to 7 are both in inverse proportional to the volume fraction of coarse secondary particles. The present work indicates that a reasonable size distribution of the secondary particles is required to improve the magnetic properties of the soft magnetic powder cores.

Gibbs–Duhem equation is one of the fundamental equations in thermodynamics, which describes the relation among changes in temperature, pressure and chemical potential. Thermodynamic system can be affected by external field, and this effect should be revealed by thermodynamic equations. Based on energy postulate and the first law of thermodynamics, the differential equation of internal energy is extended to include the properties of external fields. Then, with homogeneous function theorem and a redefinition of Gibbs energy, a generalized Gibbs–Duhem equation with influences of external fields is derived. As a demonstration of the application of this generalized equation, the influences of temperature and external electric field on surface tension, surface adsorption controlled by external electric field, and the derivation of a generalized chemical potential expression are discussed, which show that the extended Gibbs–Duhem equation developed in this paper is capable to capture the influences of external fields on a thermodynamic system.

Electrostatic field can change the pressure of dielectric system, and this effect is related to the exerted direction of the electric field. With this characteristic, enhancing mass and heat transfer can be achieved by applying external electric field. In this paper, based on the laws of thermodynamics, the fundamental equation of the dielectric system with the influences of electrostatic field was established. The mechanical equilibrium condition was deduced from this fundamental equation by the free energy criterion for thermodynamic equilibrium state, which is the effective pressure of each phases must be equal to each other. This effective pressure includes the mechanical effect of the electrostatic field on the dielectric system. It consists of two parts, real pressure within the system and the electric tension on the interface between phases, which leads to the difference of the real pressure within different phases. For a two-phase system with a planar interface, when the electric field is parallel to the phase interface, the real pressure within the phase with larger dielectric constant is larger; when the electric field is perpendicular to the phase interface, real pressure within the phase with larger dielectric constant is smaller; and while the field acts on part of the system, the real pressure in the region with electric field is higher than that without electric field. With this characteristic, the vapor pressure of gas-liquid system could be reduced with exerting electrostatic field along the direction parallel to the interface, or it could be increased when the exerting direction is perpendicular to the interface. Our conclusions derived from equilibrium thermodynamics are consistent with the electrohydrodynamic results.