Experimental study of low-temperature electrical radiant floor heating system

To evaluate the thermal performance of a low-temperature electrical radiant floor heating system,an experimental facility equipped with a constant temperature chamber and different specimen floors is designed and built.The heating cable is installed in the floor slab with a unit-rated power of 30 W/m.Twenty-four different schemes are worked out and tested,which include three kinds of composite floor structures and eight kinds of cable distances.The cable distances are 30,40,50,60,80,100,130,150 mm.The main affective factors of the thermal performance and their influencing regularity are discussed.The experimental results show that the system has good stability and reliability,and the ratio of the radiation heat-transfer rate to the gross heat-transfer rate is greater than 50%.When the floor structure and the cable distance are fixed,the gross heat-transfer rate of the upper floor surface has a maximum value at an optimal cable distance.Under the experimental conditions in this paper,the optimal cable distance is 50 mm.

Simulation and Analysis of Cascading Faults in Integrated Heat and Electricity Systems Considering Degradation Characteristics

Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading faults is no longer appropriate.A cascading fault analysis method considering multi-energy coupling characteristics is of vital importance.In this study,an innovative analysis method for cascading faults in integrated heat and electricity systems(IHES)is proposed.It considers the degradation characteristics of transmission and energy supply com-ponents in the system to address the impact of component aging on cascading faults.Firstly,degradation models for the current carrying capacity of transmission lines,the water carrying capacity and insulation performance of thermal pipelines,as well as the performance of energy supply equipment during aging,are developed.Secondly,a simulation process for cascading faults in the IHES is proposed.It utilizes an overload-dominated development model to predict the propagation path of cascading faults while also considering network islanding,electric-heating rescheduling,and load shedding.The propagation of cascading faults is reflected in the form of fault chains.Finally,the results of cascading faults under different aging levels are analyzed through numerical examples,thereby verifying the effectiveness and rationality of the proposed model and method.

Research on Operation Optimization of Heating System Based on Electric Storage Coupled Solar Energy and Air Source Heat Pump

For heating systems based on electricity storage coupled with solar energy and an air source heat pump(ECSA),choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency.In this paper,four cities in three climatic regions in China were selected,namely Nanjing in the hot summer and cold winter region,Tianjin in the cold region,Shenyang and Harbin in the severe cold winter region.The levelized cost of heat(LCOH)was used as the economic evaluation index,and the energy consumption and emissions of different pollutants were analyzed.TRNSYS software was used to simulate and analyze the system performance.The Hooke-Jeeves optimization algorithm and GenOpt software were used to optimize the system parameters.The results showed that ECSA systemhad an excellent operation effect in cold region and hot summer and cold winter region.Compared with ECS system,the systemenergy consumption,and the emission of different pollutants of ECSA system can be reduced by a maximum of 1.37 times.In cold region,the initial investment in an air source heat pump is higher due to the lower ambient temperature,resulting in an increase in the LOCH value of ECSA system.After the LOCH value of ECSA system in each region was optimized,the heating cost of the system was reduced,but also resulted in an increase in energy consumption and the emission of different pollutant gases.

Optimal Operation of Integrated Heat and Electricity Systems:A Tightening McCormick Approach

Combined heat and electricity operation with variable mass flow rates promotes flexibility,economy,and sustainability through synergies between electric power systems(EPSs)and district heating systems(DHSs).Such combined operation presents a highly nonlinear and nonconvex optimization problem,mainly due to the bilinear terms in the heat flow model—that is,the product of the mass flow rate and the nodal temperature.Existing methods,such as nonlinear optimization,generalized Benders decomposition,and convex relaxation,still present challenges in achieving a satisfactory performance in terms of solution quality and computational efficiency.To resolve this problem,we herein first reformulate the district heating network model through an equivalent transformation and variable substitution.The reformulated model has only one set of nonconvex constraints with reduced bilinear terms,and the remaining constraints are linear.Such a reformulation not only ensures optimality,but also accelerates the solving process.To relax the remaining bilinear constraints,we then apply McCormick envelopes and obtain an objective lower bound of the reformulated model.To improve the quality of the McCormick relaxation,we employ a piecewise McCormick technique that partitions the domain of one of the variables of the bilinear terms into several disjoint regions in order to derive strengthened lower and upper bounds of the partitioned variables.We propose a heuristic tightening method to further constrict the strengthened bounds derived from the piecewise McCormick technique and recover a nearby feasible solution.Case studies show that,compared with the interior point method and the method implemented in a global bilinear solver,the proposed tightening McCormick method quickly solves the heat–electricity operation problem with an acceptable feasibility check and optimality.

Pyrolysis of Huadian oil shale by electrical heating on different heating rates

The electrical heating experiments on oil shale sample from Huadian of Jilin were carried out by the pyrolysis method at three different heating rate 2℃/min, 5 ℃/min and 10 ℃/min in the temperature range of 30℃ -750℃. Heating rate 2 ℃/rain is considered low, while intermediate one covers the range 5 ℃/min and high heating rate is 10℃/min. The controlling parameters studied were the final pyrolysis temperature and the influence of the heating rate as well as type. The heating rate has an important effect on the pyrolysis of oil shale and the amount of residual carbon obtained therefore. It is found that increasing the heating rate and py- rolysis temperature also increases the production of oil and the total weight loss. Higher heating rates resulted in higher rates of accumulation. The rate of oil and water collection passed through the maximum of different heat- ing rates at different pyrolysis temperatures. Heating rate affected density, oil conversion and oil yield.

Study on the Pyrolytic Carbon Generated by the Electric Heating CVD Method

A new method of fabricating C/C composite materials, namely electric heating CVD method, was used, which electrified the carbon fiber directly by using the conductivity of itself. Acetylene was used as the carbon source with nitrogen as dilution gas, and the pyrolytic carbon started to deposit on the carbon fiber surface when the deposition temperature was reached. The morphology of pyrolytic carbon was characterized by SEM, and the surface properties of carbon fibers before and after CVD were characterized by Raman spectroscopy. The experimental results show that the electric heating method is a novel method to fabricate C/C composite materials, which can form a dense C/C composite material in a short time. The order degree and the average crystallite size of the carbon fiber surface were decreased after the experiment.

Catalytic CVD Growth of Carbon Nanotubes by Electric Heating Method

Carbon nanotubes（CNTs） were synthesized by the electric heating catalytic chemical deposition method（CCVD） using acetylene（C2H2） as the carbon source and nitrogen（N2） as carrier gas,and nickel catalyst was loaded by electroplating.The electric heating method,as a new method,electrifies the carbon fiber directly by using its conductivity.The morphology and structure of CNTs were characterized by SEM and TEM,and the surface properties of carbon fibers before and after the growth of CNT were characterized by Raman spectroscopy.The experimental results show that the electric heating method is a new method to produce CNT,and can grow a large number of CNTs in a short time,the crystallization degree and surface average crystallite size of carbon fiber increased after the growth of CNT on it.In addition,electroplating loading catalyst can also be used as an ideal loading way,which can control the number,shape,and distribution of nickel particles by controlling the plating time.

COUPLED ELECTRICAL-THERMAL-MECHANICAL ANALYSIS FOR ELECTRICAL/LASER HEATING ASSISTED BLANKING

A coupled electrical-thermal-mechanical analysis is conducted for electrical/laser heating assisted blanking. Two novel localized-heating methods, electrical heating and laser-heating, recently proposed for small-part blanking, are investigated with FE simulations. Results show that electrical heating would result in an advantageous distribution of temperature in a 316 stainless steel work-material. A desired temperature distribution may also be achievable for a copper work-material, if laser beam is used. Both electrical heating and laser-heating enable to reduce the blanking force and increase the aspect ratio achievable by blanking. The simulation also demonstrates that both electrical heating and laser-heating can result in desired temperature-distributions at sufficiently high heating-rates, ease of implementation and application. Comparatively, electrical heating could generate more favorable temperature distribution for small-part blanking.

Observability Analysis of Integrated Electricity and Heating Systems with Thermal Quasi-dynamics in Pipelines

Observability analysis(OA)is vital to obtaining the available input measurements of state estimation(SE)in an integrated electricity and heating system(IEHS).Considering the thermal quasi-dynamics in pipelines,the measurement equations in heating systems are dependent on the estimated results,leading to an interdependency between OA and SE.Conventional OA methods require measurement equations be known exactly before SE is performed,and they are not applicable to IEHSs.To bridge this gap,a scenario-based OA scheme for IEHSs is devised that yields reliable analysis results for a predefined set of time-delay scenarios to cope with this interdependency.As its core procedure,the observable state identification and observability restoration are formulated in terms of integer linear programming.Numerical tests are conducted to demonstrate the validity and superiority of the proposed formulation.

Influence of heat loss through probe electrical leads on thermal conductivity measurement with TPS method

The transient plane source(TPS)method is developed recently to measure the thermal conductivity of materials.In the measurement,the heating power is influenced by the heat which is transferred via the probe electrical leads.This fact further influences the measurement accuracy of thermal conductivity.To solve this problem,the influence of heat loss through the electrical leads on the heating power is studied theoretically.The mathematical formula of heat loss is deduced,and the corresponding correction model is presented.A series of measurement experiments on different materials have been conducted by using the hot disk thermal constant analyzer.The results show that the influence of the heat loss on the measurement is sensitive to different test materials and probes with different sizes.When the thermal conductivity of the material is greater than 0.2 W/(m·K),the influence of the heat loss is less than 0.16%,which can be ignored.As to the lower thermal conductivity materials,it is necessary to compensate the heat loss through the electrical leads,and the accuracy of thermal conductivity measurement can be effectively improved.

Coordinated control strategy for wind power accommodation based on electric heat storage and pumped storage

To solve the severe problem of wind power curtailment in the winter heating period caused by ＂power determined by heat＂ operation constraint of cogeneration units, this paper analyzes thermoelectric load, wind power output distribution and fluctuation characteristics at different time scales, and finally proposes a two level coordinated control strategy based on electric heat storage and pumped storage. The optimization target of the first level coordinated control is the lowest operation cost and the largest wind power utilization rate. Based on prediction of thermoelectric load and wind power, the operation economy of the system and wind power accommodation level are improved with the cooperation of electric heat storage and pumped storage in regulation capacity. The second level coordinated control stabilizes wind power real time fluctuations by cooperating electric heat storage and pumped storage in control speed. The example results of actual wind farms in Jiuquan, Gansu verifies the feasibility and effectiveness of the proposed coordinated control strategy.

Photon-Assisted Heat Generation by Electric Current in a Quantum Dot Attached to Ferromagnetic Leads

Heat generated by electric current in a quantum dot device contacting a phonon bath is studied using the non- equilibrium Green function technique. Spin-polarized current is generated owing to the Zeeman splitting of the dot level. The current＇s strength and the spin polarization are further manipulated by changing the frequency of an applied photon field and the ferromagnetism on the leads. We find that the associated heat by this spin- polarized current emerges even if the bias voltage is smaller than the phonon energy quanta and obvious negative differential of the heat generation develops when the photon frequency exceeds that of the phonon. It is also found that both the strength and the resonant peaks＇ position of the heat generation can be tuned by changing the value and the arrangement configurations of the magnetic moments of the two leads, and then provides an effective method to generate large spin-polarized current with weak heat. Such a result may be useful in designing low energy consumption spintronic devices.

Research on Performance Optimization of Phase Change Thermal Storage Electric Heating Device

At present, the main heating method for reducing crude oil viscosity is electric heating, and the all-day electric heating method has the problems of high energy consumption and high cost. In order to meet the needs of environmental protection and industrial production, a new type of phase change thermal storage electric heating device was designed by combining the crude oil viscosity reduction heating method with valley price and phase change materials. The results indicate that as the inlet flow rate of the working fluid increases, the outlet temperature continuously decreases. And when the outlet temperature rises to 10?C, the inlet flow rate of the device can meet the flow range of 1.413 - 2.120 m3/h. At the same time, the addition of foam nickel makes the internal temperature of PCM more uniform, and the internal temperature of PCM decreases with the decrease of porosity of foam metal. By increasing the number of electric heating rods and reducing the power of individual electric heating rods, the structure of the device was optimized to significantly improve local high-temperature phenomena. The use of this device can maintain high heat exchange efficiency and reduce production costs.

Quasi-dynamic Interactions and Security Control of Integrated Electricity and Heating Systems in Normal Operations

Coupling between electricity systems and heating systems are becoming stronger,leading to more flexible and more complex interactions between these systems.The operation of integrated energy systems is greatly affected,especially when security is concerned.Steady-state analysis methods have been widely studied in recent research,which is far from enough when the slow thermal dynamics of heating networks are introduced.Therefore,an integrated quasi-dynamic model of integrated electricity and heating systems is developed.The model combines a heating network dynamic thermal model and the sequential steady-state models of electricity networks,coupling components,and heating network hydraulics.Based on this model,a simulation method is proposed and quasi-dynamic interactions between electricity systems and heating systems are quantified with the highlights of transport delay.Then the quasi-dynamic interactions were applied using security control to relieve congestion in electricity systems.Results show that both the transport delay and control strategies have significant influences on the quasi-dynamic interactions.

Fabrication of patterned transparent conductive glass via laser metal transfer for efficient electrical heating and antibacteria

Vapor deposition and three-dimensional(3D)printing technology are considered to be conventional methods to achieve patterned metal film preparation through the assistance of masks and high temperature.Therefore,there are still some challenges in fabricating metal films in template-free and normal temperature environment.In this work,we report a flexible and rapid laser metal transfer(LMT)technique for fabricating the various metal films(Cu,Ni,Sn,Al,Fe,and Ag)with different patterns without templates on arbitrary substrates(glass,polyimide(PI)films,and aluminum nitride(AlN)ceramic).Especially,the obtained transparent conductive glass displays high transmittance(more than 90%)and adjustable resistances(≈5Ω).According to the Joule effect,the interface resistance between Cu particles and copper oxide coating produces the high temperature approximately 280℃ at 2 V in a short time(≈60 s)and remains stable at 120℃ over 12 h.At last,the multifunctional glass with Cu patterns also shows excellent bactericidal activity(≈95%).This work demonstrates that laser metal transfer is an exceeding effective means of fabricating the micro/nano structures with potential applications in functional devices.

Effects of nano-metal oxide additives on ignition and combustion properties of MICs-boron rich fuels

Boron has been considered a promising powdered metal fuel for enhancing composite propellants'energy output due to its high energy density.However,the high ignition temperature and low combustion efficiency limit the application of boron powder due to the high boiling point of the boron oxide layer.Much research is ongoing to overcome these shortcomings,and one potential approach is to introduce a small quantity of metal oxide additives to promote the reaction of boron.This study prepared boron-rich fuels with 10 wt%of eight nano-metal oxide additives by mechanical ball milling.The effect of metal oxides on the thermo-oxidation,ignition,and combustion properties of boron powder was comprehensively studied by the thermogravimetric analysis(TG),the electrically heated filament setup(T-jump),and the laser-induced combustion experiments.TG experiments at 5 K/min found that Bi_(2)O_(3),MoO_(3),TiO_(2),Fe_(2)O_(3),and CuO can promote thermo-oxidation of boron.Compared to pure boron,Tonsetcan be reduced from 569℃to a minimum of 449℃(B/Bi_(2)O_(3)).Infrared temperature measurement in T-jump tests showed that when heated by an electric heating wire at rates from 1000 K/s to 25000 K/s,the ignition temperatures of B/Bi_(2)O_(3) are the lowest,even lower than the melting point of boron oxide.Ignition images and SEM for the products further showed that the high heating rate is beneficial to the rapid reaction of boron powder in the single-particle combustion state.Fuels(B/Bi_(2)O_(3),B/MoO_(3),and B/CuO)were mixed with the oxidant AP and ignited by laser to study the combustion performance.The results showed that B/CuO/AP has the largest flame area,the highest BO_(2) characteristic spectral intensity,and the largest burn rate for powder lines.To combine the advantages of CuO and Bi_(2)O_(3),binary metal oxide(CBO,mass ratio of 3:1)was prepared and the test results showed that CBO can very well improve both ignition and combustion properties of boron.Especially B/CBO/AP has the highest burn rate compared with all fuels containing other additives.It was found that multi-component metal-oxide additive can more synergistically improve the reaction characteristics of boron powder than unary additive.These findings contribute to the development of boron-rich fuels and their application in propellants.

Multi-energy Storage System Model Based on Electricity Heat and Hydrogen Coordinated Optimization for Power Grid Flexibility

Based on decreasing the flexibility of the power grid through the integration of large-scale renewable energy,a multi-energy storage system architectural model and its coor-dination operational strategy with the same flexibility as in the pumped storage power station and battery energy storage system(BESS)are studied.According to the new energy fluctuation characteristics and the different peak valley parameters in the power grid,this paper proposes a electricity heat hydrogen multi-energy storage system(EHH-MESS)and its coordination and optimization operational model to reduce the curtailment of wind power and photovoltaic(PV)to the power grid and improve the flexibility of the power grid.Finally,this paper studied the simulation model of an energy storage optimization control strategy after the multi-energy storage system is connected to the distribution networks,and analyzed three operational modes of the multi-energy storage system.The simulation results show that the EHH-MESS proposed in this paper has a better power grid regulation flexibility and economy,and can be used to replace the battery energy storage system based on MATLAB.

A Deep Neural Network Coordination Model for Electric Heating and Cooling Loads Based on IoT Data

As the ubiquitous electric power internet of things(UEPIoT)evolves and IoT data increases,traditional scheduling modes for load dispatch centers have yielded a variety of chal-lenges such as calculation of real-time optimization,extraction of time-varying characteristics and formulation of coordinated scheduling strategy for capacity optimization of electric heating and cooling loads.In this paper,a deep neural network coor-dination model for electric heating and cooling loads based on the situation awareness(SA)of thermostatically controlled loads(TCLs)is proposed.First,a sliding window is used to adaptively preprocess the IoT node data with uncertainty.According to personal thermal comfort(PTC)and peak shaving contribution(PSC),a dynamic model for loads is proposed;meanwhile,personalized behavior and consumer psychology are integrated into a flexible regulation model of TCLs.Then,a deep Q-network(DQN)-based approach,using the thermal comfort and electricity cost as the comprehensive reward function,is proposed to solve the sequential decision problem.Finally,the simulation model is designed to support the validity of the deep neural network coordination model for electric heating and cooling loads,by using UEPIoT intelligent dispatching system data.The case study demonstrates that the proposed method can efficiently manage coordination with large-scale electric heating and cooling loads.

Electrical Conductivity,Oil Absorption and Electric Heating of Carbon Black-modified Carbon Nanofibers

Carbon-black-modified carbon nanofibers were prepared by electrospinning,and the effects of the carbon black content and processing temperature on the physical and chemical properties of the resulting composites were investigated.The results showed that the conductivity of carbon-black-modified nanofibers increased with the carbon black content.The addition of carbon black in a 20%mass ratio increased the conductivity of the composite(0.75 S/cm)by 230%compared with the undoped nano-fiber(2.47 S/cm),while the adulteration with 5%CB allowed the preservation of the mechanical properties of the composites.The fabricated carbon-black/carbon-nanocomposite fibers exhibited excellent oil absorption and electrothermal conversion performance.Furthermore,the conductivity and oil absorption capacity increased with increasing carbonization temperature.With a carbonization temperature of 1000℃(5%carbon black),the voltage was 31 V,the current was 0.66 A,and the surface temperature of the composite reached 234.1℃.The overall enhancement in physical properties upon the addition of even low amounts of carbon black makes these composites advantageous for future industrial applications.

Boosting methylcyclohexane dehydrogenation over Pt-based structured catalysts by internal electric heating

Methylcyclohexane(MCH)serves as an ideal hydrogen carrier in hydrogen storage and transportation process.In the continuous production of hydrogen from MCH dehydrogenation,the rational design of energy-efficient catalytic way with good performance remains an enormous challenge.Herein,an internal electric heating(IEH)assisted mode was designed and proposed by the directly electrical-driven catalyst using the resistive heating effect.The Pt/Al2O_(3)on Fe foam(Pt/Al2O_(3)/FF)with unique threedimensional network structure was constructed.The catalysts were studied in a comprehensive way including X-ray diffraction(XRD),scanning electron microscopy(SEM)-mapping,in situ extended X-ray absorption fine structure(EXAFS),and in situ COFourier transform infrared(FTIR)measurements.It was found that the hydrogen evolution rate in IEH mode can reach up to above 2060 mmol·gPt^(−1)·min^(−1),which is 2–5 times higher than that of reported Pt based catalysts under similar reaction conditions in conventional heating(CH)mode.In combination with measurements from high-resolution infrared thermometer,the equations of heat transfer rate,and reaction heat analysis results,the Pt/Al2O_(3)/FF not only has high mass and heat transfer ability to promote catalytic performance,but also behaves as the heating component with a low thermal resistance and heat capacity offering a fast temperature response in IEH mode.In addition,the chemical adsorption and activation of MCH molecules can be efficiently facilitated by IEH mode,proved by the operando MCH-FTIR results.Therefore,the as-developed IEH mode can efficiently reduce the heat and mass transfer limitations and prominently boost the dehydrogenation performance,which has a broad application potential in hydrogen storage and other catalytic reaction processes.