Heating Scheme Research Articles

Non-Maxwellian fast particle effects in gyrokinetic GENE simulations

Fast ions have recently been found to significantly impact and partially suppress plasma turbulence both in experimental and numerical studies in a number of scenarios. Understanding the underlying physics and identifying the range of their beneficial effect is an essential task for future fusion reactors, where highly energetic ions are generated through fusion reactions and external heating schemes. However, in many of the gyrokinetic codes fast ions are, for simplicity, treated as equivalent-Maxwellian-distributed particle species, although it is well known that to rigorously model highly non-thermalised particles, a non-Maxwellian background distribution function is needed. To study the impact of this assumption, the gyrokinetic code GENE has recently been extended to support arbitrary background distribution functions which might be either analytical, e.g., slowing down and bi-Maxwellian, or obtained from numerical fast ion models. A particular JET plasma with strong fast-ion related turbulence suppression is revised with these new code capabilities both with linear and nonlinear gyrokinetic simulations. It appears that the fast ion stabilization tends to be less strong but still substantial with more realistic distributions, and this improves the quantitative power balance agreement with experiments.

Forecasting severe convective storms with WRF-based RTFDDA radar data assimilation in Guangdong, China

Radar data assimilation is an important method for short-term convection forecasting or nowcasting. To improve the short-term (mainly 0–3 h) precipitation forecasts for severe convective storms, an analysis nudging (Newtonian relaxation) based hydrometeor and latent heat nudging (HLHN) technique was developed to effectively assimilate radar reflectivity data in a Weather Research and Forecasting (WRF)-based real time four-dimensional data assimilation and short-term forecasting system (RTFDDA). The purpose of this study is to investigate the performance of the RTFDDA system with radar data assimilation (RTFDDA-RDA) with rapid-cycling forecasting applications for Shenzhen, a subtropical coastal metropolis in southern China. The RTFDDA-RDA system was run to produce hindcasts for ten severe convective storm events occurred in Guangdong region during the 2017 rainy season. Results show that, through nudging cloud hydrometeors retrieved from radar reflectivity and the associated latent heat release, RTFDDA-RDA is able to produce the meso- and convective-scale features of the convective storms in a good accuracy and improve the short-term precipitation forecasting of the convective storms. Subjective and statistical evaluation results demonstrate that RTFDDA-RDA presents a reasonable capability for forecasting convective systems with improving the initial conditions and resulting in significant improvements of precipitation forecasting skills, especially for the 0–3-h nowcasting range. The sensitivity experiments on different latent heating schemes show that, the convective-stratiform separated heating scheme has the best performance of forecasts. Finally, intercomparison of different radar data assimilation approaches will be conducted in future.

Scrap tyre pyrolysis: Modified chemical percolation devolatilization (M-CPD) to describe the influence of pyrolysis conditions on product yields

This paper attempts to develop a modified chemical percolation devolatilization (M-CPD) model that can include heat transfer, primary pyrolysis and the secondary cracking reactions of volatiles together to describe the pyrolysis of waste scrap tyre chip, as well as to examine the influence of operating conditions on the scrap tyre pyrolysis product yields. Such a study has yet to be conducted in the past, thereby leading to a large knowledge gap failing to understand the pyrolysis of the coarse feedstock appropriately. To validate the developed model, a number of operating parameters including reactor configurations, carrier gas compositions (argon and argon blended with CO2 and/or steam), scrap tyre chip size (0.5–15.0 mm), terminal pyrolysis temperature (400–800 °C) and heating rate (10 °C/min and 110 °C/min) were examined in a lab-scale fixed-bed pyrolyser, with a particular focus on the secondary cracking extents of the liquid tar. Through both experimental investigation and modelling approach, it was found that significant secondary cracking extent occurred upon the increase in the feedstock size, heating rate and residence time. Upon the fast pyrolysis, the average temperature gap between the centres of the coarse particle and reactor wall could reach a maximum of 115 °C for the tyre chips of 6–15 mm. Consequently, its primary volatiles underwent the secondary cracking reaction at an overall extent of 17% at a terminal temperature of 600 °C and a fast heating rate of 110 °C/min. Consequently, the yield of light gases including methane was increased remarkably. The flow rate of inert carrier gas was also influential in the secondary cracking, in which a maximum tar yield (54 wt%) was reached at a carrier gas flow rate of 1.5 L/min. This indicates the occurrence of secondary cracking has been largely minimised. At a pyrolysis temperature of 600 °C, the addition of CO2 in the carrier gas had an insignificant effect on the product yield distribution under the slow heating scheme. In contrast, the addition of steam resulted in a slight increase of carbon monoxide, presumably due to the occurrence of gasification reaction.

AIR-RADIANT HEATING ON THE BASIS OF A TWO-FLOW HEAT GENERATOR WITH INFRARED EMITTERS

A scheme of a radiant heating regenerative system on the basis of a two-fl ow heat generator, and system and form of heat-radiating air ducts is proposed. It is shown that the system of radiant heating is more effi cient as compared to the conventional convection system. Traditionally, the convective scheme of heating is used wherein radiators installed near the fl oor are used. Water serves as the working fl uid in the radiators. The proposed radiant heating regenerative system is based on the transfer of heat in the form of infrared electromagnetic radiation. An effi cient two-fl ow heat generator with infrared emitt ers has been developed, which gives off heat only from the radiating surface of heat exchangers. This system allows you to reduce investment, operating costs and improve the effi ciency of the heating system.

Thermodynamic Efficiency of Heat Pump Heating Scheme Using Ground and Sewage Heat

Background. Currently, the development and research of thermodynamic or energy efficiency of combined heat pump heat supply systems with the use of several low-temperature sources of energy becomes relevant. Objective. The aim of the paper is to determine the dependence of the relative productivity of the vertical ground heat exchanger on the hot water heat consumption by the building and the ambient temperature. Methods. A thermodynamic analysis of scheme was carried out, on the basis of which conclusions were made on improving the working conditions of combined heat pump heat supply system and reducing the specific energy consumption for heat generation in the heating system. Results. The correlation for determining the total specific energy expenditure for the heat pump system with the use of ground and sewage heat is obtained. It is shown that the heat pump heating system scheme with the use of additional sewage heat is more effective than the initial heating scheme. The effectiveness depends on the consumption of hot water in the building, and the ambient temperature. Conclusions. It is determined that using this scheme in designing the heat pump heating system can significantly reduce capital and operating costs. The use of obtained dependencies in the development of heat pump systems will ensure the maximum energy efficiency of their operation.

Heat-electrical regeneration way to intensive energy saving in an electric arc furnaces

Energy saving in steel production is of great significance for its large economical scale of 1500 mil t/year and high-energy consumption. Steady trend of last years is an increase of steel production in electric arc furnaces (EAF) with a very high consumption of electricity up to 750 kWh/ton. The intention to reduce so much energy consumption they can reach by many ways. One of such way is a transforming heat energy of liquid steel to electricity and destine it to steel electric arc process. Under certain conditions, it may lead to “zero” consumption of electric power in the process. The development of these conditions leads to the formation of energy-efficient heat schemes, with a minimum electricity consumption from the external network.

Experimental study of heating scheme effect on the inner divertor power footprint widths in EAST lower single null discharges

A comprehensive work of the effects of plasma current and heating schemes on divertor power footprint widths is carried out in the experimental advanced superconducting tokamak (EAST). The divertor power footprint widths, i.e., the scrape-off layer heat flux decay length λq and the heat spreading S, are crucial physical and engineering parameters for fusion reactors. Strong inverse scaling of λq and S with plasma current have been demonstrated for both neutral beam (NB) and lower hybrid wave (LHW) heated L-mode and H-mode plasmas at the inner divertor target. For plasmas heated by the combination of the two kinds of auxiliary heating schemes (NB and LHW), the divertor power widths tend to be larger in plasmas with higher ratio of LHW power. Comparison between experimental heat flux profiles at outer mid-plane (OMP) and divertor target for NB heated and LHW heated L-mode plasmas reveals that the magnetic topology changes induced by LHW may be the main reason to the wider divertor power widths in LHW heated discharges. The effect of heating schemes on divertor peak heat flux has also been investigated, and it is found that LHW heated discharges tend to have a lower divertor peak heat flux compared with NB heated discharges under similar input power. All these findings seem to suggest that plasmas with LHW auxiliary heating scheme are better heat exhaust scenarios for fusion reactors and should be the priorities for the design of next-step fusion reactors like China Fusion Engineering Test Reactor.

Keeping warm: a review of deep geothermal potential of the UK

In 2015, the primary energy demand in the UK was 202.5 million tonnes of oil equivalent (mtoe = 848 EJ). Of this, about 58 mtoe (2.43 EJ) was used for space heating. Almost all of this heat was from burning fossil fuels either directly (50% of all gas used is for domestic purposes) or indirectly for power generation. Burning fossil fuels for heat released about 160 million tonnes of carbon dioxide in 2015. The UK must decarbonise heating for it to meet its commitments on emissions reduction. UK heat demand can be met from ultra-low-carbon, low enthalpy geothermal energy. Here we review the geothermal potential of the UK, comprising a combination of deep sedimentary basins, ancient warm granites and shallower flooded mines. A conservative calculation of the contained accessible heat in these resources is 200 EJ, about 100 years supply. Presently only one geothermal system is exploited in the UK. It has been supplying about 1.7MWT (heat) to Southampton by extracting water at a temperature of 76 ℃ from a depth of 1.7 km in the Wessex Basin. Like Southampton, most of the major population centres in the UK lie above or adjacent to major geothermal heat sources. The opportunity for using such heat within district heating schemes is considerable. The consequences of developing a substantial part of the UK’s geothermal resource are profound. The baseload heating that could be supplied from low enthalpy geothermal energy would cause a dramatic fall in the UK’s emissions of greenhouse gases, reduce the need for separate energy storage required by the intermittent renewables (wind and solar) and underpin a significant position of the nation’s energy security for the foreseeable future, so lessening the UK’s dependence on imported oil and gas. Investment in indigenous energy supplies would also mean retention of wealth in the UK.

Tailored properties of hot stamping steel by resistance heating with local temperature control

Local austenization by local heating temperature control of blanks is one of the methods to obtain hot stamping parts with tailored properties. Resistance heating is a novel heating technology with high efficiency and rapid heating rate. In this paper, a heat transfer model was firstly developed to describe the steady temperature distribution of the blank during resistance heating. Then two resistance heating schemes to achieve tailored properties of hot stamping steel were investigated by experiments. One scheme is local resistance heating by adjusting the electrode position. And the other scheme is resistance heating with middle insulation. The results showed that the developed model could provide adequate accuracy in calculating the blank temperature field. For the local resistance heating, the percentage of high temperature region in heating zone was about 70 %. From the non-heating region to the middle heating region, hardness increased from 200 to 515 HV10. And the length ratio between high and low hardness regions could he controlled by adjusting electrode positions. For the resistance heating with middle insulation, a 340~360 HV10 medium hardness region with the length of 80mm was observed. The total length of transition hardness regions was about 60 mm. In summary, the local resistance heating scheme showed more advantages including shorter transition region and significant hardness difference.

Identification of thermal conductivity between external air and the case of the equivalent heat scheme of substitution of the asynchronous traction engine of a traw wagon

The article is devoted to the method of determining the thermal conductivity between the external air and the equivalent thermal circuit for the replacement of an asynchronous traction motor with IP 54 protection level, which is used on tram cars. The specific features of the technique is the determination of conductivity, taking into account the thermal resistances between the following surfaces: the outer surface of the drooping part of the frame on the drive side and the outside air; The outer surface of the bed above the bag and the outside air, the outer surface of the hanging part of the frame on the fan side and the outside air, the outer surface of the bearing shield on the drive side and the outside air, and between the outer surface of the bearing shield on the fan side and the outside air.According to the proposed method, the thermal conductivities between the external air and the hull for the asynchronous traction engine of the tram car AD 931 were determined with parameters with different engine speeds. It was shown that the thermal conductivity between the external air and the body increases from 6.13 W / K at 10 rpm to 93.5 W / K at 4400 rpm, which significantly affects the thermal conditions of the engine.

Modeling and optimization for hydraulic performance design in multi-source district heating with fluctuating renewables

Hydraulic performance of a district heating system is a significant aspect in designing. In the context of multiple heat sources and looped topology layout, severe non-linear hydraulic characteristics have markedly impacts on the hydraulic performance design of a district heating network. Design or select variable-speed circulating pumps with suitable capacities and hydraulic characteristics can be a rather difficult issue especially when there are fluctuating renewable heat sources. In this paper, an optimization model is proposed to achieve the lowest power consumption of all pumps and still fulfill the hydraulic head demands of all substations simultaneously. Based on the proposed model, a holistic design method is presented for optimal hydraulic design of the variable-speed pumps in each heat source. Then a case study is illustrated to validate the proposed method. With consideration of fluctuating heat load of a renewable heat source, the optimal rated capacities of all pumps and variable speed hydraulic characteristic curves are obtained in the designed heating schemes from 100% to 40% of full heat load. Moreover, when all pumps operating on their optimal regime, there always exists one substation branch whose excess head would reach the preset minimum value. The sensitivity analysis results show that the variation of total work of pumps can be from 0.16% to 7.56% when the heat load of the renewable heat source fluctuated 1.0% in different designed heating schemes.

Parametric dependencies of the experimental tungsten transport coefficients in ICRH and ECRH assisted ASDEX Upgrade H-modes

The profiles of the W transport coefficients have been experimentally calculated for a large database of identical ASDEX Upgrade H-mode discharges where only the radio-frequency (RF) power characteristics have been varied [Angioni et al., Nucl. Fusion 57, 056015 (2017)]. Central ion cyclotron resonance heating (ICRH) in the minority heating scheme has been compared with central and off-axis electron cyclotron resonance heating (ECRH), using both localized and broad heat deposition profiles. The transport coefficients have been calculated applying the gradient-flux relation to the evolution of the intrinsic W density in-between sawtooth cycles as measured using the soft X-ray diagnostic. For both ICRH and ECRH, the major player in reducing the central W density peaking is found to be the reduction of inward pinch and, in the case of ECRH, the rise of an outward convection. The impurity convection increases, from negative to positive, almost linearly with RF-power, while no appreciable changes are observed in the diffusion coefficient, which remains roughly at neoclassical levels independent of RF power or background plasma conditions. The ratio vW/DW is consistent with the equilibrium ∇nW/nW prior to the sawtooth crash, corroborating the separate estimates of diffusion and convection. These experimental findings are slightly different from previous results obtained analysing the evolution of impurity injections over many sawtooth cycles. Modelling performed using the drift-kinetic code NEO and the gyro-kinetic code GKW (assuming axisymmetry) overestimates the diffusion coefficient and underestimates the experimental positive convection. This is a further indication that magneto-hydrodynamic/neoclassical models accounting for 3D effects may be needed to characterize impurity transport in sawtoothing tokamak plasmas.

The effect of synthesis and thermal treatment on phase composition and ionic conductivity of Na-doped SrSiO3

The structural and electrochemical properties of Sr1-xNaxSiO3 were studied. Powders with different compositions (0.1≤x≤0.45) were prepared by solid state reaction. Mixing of SrCO3, Na2CO3 and SiO2 was carried out in different media in order to explore the effect of solvents on the formation of secondary phases. X-ray diffraction was employed to study the phase composition of mixtures treated in air at different temperatures in the range 850–1050°C for at least 12h. Various heating schemes were applied to help the incorporation of Na in the monoclinic SrSiO3 structure.Pressed pellets were sintered at 1000°C for at least 12h and electroded with Ag paste for electrochemical characterization.For most compositions and thermal treatments, the formation of the insulating Na2Si2O5 phase was observed, as reported in literature.Highest conductivity and degradation rate was obtained when synthesis was carried out in acetone with single calcination step at 850°C, due to the crystallization of Na2Si2O5 from glass. Double calcination limited conductivity but increased its thermal stability. When ethanol was used for powder mixing and double calcination was applied, the material exhibited higher conductivity after long term ageing at 650°C, also thanks to its low activation energy, without appreciable crystallization of other silicates.

Temperature measurement of hohlraum radiation for energy loss experiments in indirectly laser heated carbon plasma.

For ion energy loss measurements in plasmas with near solid densities, an indirect laser heating scheme for carbon foils has been developed at GSI Helmholtzzentrum für Schwerionenforschung GmbH (Darmstadt, Germany). To achieve an electron density of 10^{22}cm^{3} and an electron temperature of 10-30eV, two carbon foils with an areal density of 100μg/cm^{2} heated in a double-hohlraum configuration have been chosen. In this paper we present the results of temperature measurements of both primary and secondary hohlraums for two different hohlraum designs. They were heated by the PHELIX laser with a wavelength of 527nm and an energy of 150J in 1.5ns. For this purpose the temperature has been investigated by an x-ray streak camera with a transmission grating as the dispersive element.

Design study on the efficiency of the thermal scheme of power unit of thermal power plants in hot climates

At the stage of pre-proposals unit of the thermal power plants for regions with a hot climate requires a design study on the efficiency of possible options for the structure of the thermal circuit and a set of key parameters. In this paper, the thermal circuit of the condensing unit powerfully 350 MW. The main feature of the external conditions of thermal power plants in hot climates is the elevated temperature of cooling water of the turbine condensers. For example, in the Persian Gulf region as the cooling water is sea water. In the hot season of the year weighted average sea water temperature of 30.9 °C and during the cold season to 22.8 °C. From the turbine part of the steam is supplied to the distillation-desalination plant. In the hot season of the year heat scheme with pressure fresh pair of 23.54 MPa, temperature 570/560 °C and feed pump with electric drive (EDP) is characterized by a efficiency net of 0.25% higher than thermal schem with feed turbine pump (TDP). However, the supplied power unit with PED is less by 11.6 MW. Calculations of thermal schemes in all seasons of the year allowed us to determine the difference in the profit margin of units of the TDP and EDP. During the year the unit with the TDP provides the ability to obtain the profit margin by 1.55 million dollars more than the unit EDP. When using on the market subsidized price of electricity (Iran) marginal profit of a unit with TDP more at 7.25 million dollars.

Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model

Efficient high-harmonic fast-wave (HHFW) heating in the National Spherical Torus Experiment Upgrade (NSTX-U) would facilitate experiments in turbulence, transport, fast-ion studies, and more. However, previous HHFW operation in NSTX exhibited a large loss of fast-wave power to the divertor along the scrape-off layer field lines for edge densities above the fast-wave cutoff. It was postulated that the wave amplitude is enhanced in the scrape-off layer due to cavity-like modes, and that these enhanced fields drive sheath losses through RF rectification. As part of ongoing work to confirm this hypothesis, we have developed a cylindrical cold-plasma model to identify and understand scenarios where a substantial fraction of wave power is confined to the plasma periphery. We previously identified a peculiar class of modes, named annulus resonances, that conduct approximately half of their wave power in the periphery and can also account for a significant fraction of the total wave power. Here, we study the influence of annulus resonances on wave field reconstructions and find instances where annulus-resonant modes dominate the spectrum and trap over half of the total wave power at the edge. The work is part of an ongoing effort to determine the mechanism underlying these scrape-off layer losses in NSTX, identify optimal conditions for operation in NSTX-U, and predict whether similar losses occur for the ion-cyclotron minority heating scheme for both current experiments and future devices such as ITER.

Using air source heat pump air heater(ASHP-AH) for rural space heating and power peak load shifting

In order to mitigate the severe atmospheric pollution caused by the gas emission of scattered coal consumption during winter in the Beijing-Tianjin-Tangshan area, a winter space heating scheme based on the use of an air source heat pump is proposed. This scheme offers clean heating in rural areas by enhancing the efficiency of electric peak adjustment through peak shifting. The paper firstly introduces how to use air source heat pumps to replace heating stoves for rural residential heating, then explains how to use this heating method to adjust power peak load. Finally, computation analysis and experimental verification was carried out to show the effects on the power grid in the Beijing-Tianjin-Hebei area and on farmer households if all the 6 million farmer households in the Beijing-Tianjin-Hebei Region were to use this heating method.

Modelling and optimising the marginal expansion of an existing district heating network

Although district heating networks have a key role to play in tackling greenhouse gas emissions associated with urban energy systems, little work has been carried out on district heating networks expansion in the literature. The present article develops a methodology to find the best district heating network expansion strategy under a set of given constraints. Using a mixed-integer linear programming approach, the model developed optimises the future energy centre operation by selecting the best mix of technologies to achieve a given purpose (e.g. cost savings maximisation or greenhouse gas emissions minimisation). Spatial expansion features are also considered in the methodology.Applied to a case study, the model demonstrates that depending on the optimisation performed, some building connection strategies have to be prioritised. Outputs also prove that district heating schemes' financial viability may be affected by the connection scenario chosen, highlighting the necessity of planning strategies for district heating networks. The proposed approach is highly flexible as it can be adapted to other district heating network schemes and modified to integrate more aspects and constraints.

Optimization modeling for smart operation of multi-source district heating with distributed variable-speed pumps

Smart district heating integrated various advanced technologies to implement the motivation structures and minimum operation cost. In this paper, an exact mathematical model has developed to describe the thermal and hydraulic characteristics of a district heating system which applied the distributed variable-speed pumps. Afterwards, two associate optimization models have been established and the relevant regulation methods have been introduced to fulfill all customers' heat demands with less operation cost and more rapid regulation response. The proposed two co-operative approaches, which mean “coarse tuning” and “fine tuning”, have been then performed in a district heating system in Dezhou, China as a case study. Results indicate that the economical operating and less response time can be achieved simultaneously when the two proposed approaches are combined together. In contrast to the conventional approach, the total operation costs decreased by 4.99%, 11.39%, and 22.73%, respectively, in the concerned three scenarios. Moreover, the heat losses of the heating scheme can be decreased of 12.72%, 9.73%, and 4.47% at the same time. The results obviously demonstrate the great advantages and potentials of this smart operation approaches in the practical application.

Divertor heat flux simulations in ELMy H-mode discharges of EAST

This paper presents heat flux simulations for the ELMy H-mode on the Experimental Advanced Superconducting Tokamak (EAST) using a six-field two-fluid model in BOUT++. Three EAST ELMy H-mode discharges with different plasma currents Ip and geometries are studied. The trend of the scrape-off layer width with Ip is reproduced by the simulation. The simulated width is only half of that derived from the EAST scaling law, but agrees well with the international multi-machine scaling law. Note that there is no radio-frequency (RF) heating scheme in the simulations, and RF heating can change the boundary topology and increase the flux expansion. Anomalous electron transport is found to contribute to the divertor heat fluxes. A coherent mode is found in the edge region in simulations. The frequency and poloidal wave number are in the range of the edge coherent mode in EAST. The magnetic fluctuations of the mode are smaller than the electric field fluctuations. Statistical analysis of the type of turbulence shows that the turbulence transport type (blobby or turbulent) does not influence the heat flux width scaling. The two-point model differs from the simulation results but the drift-based model shows good agreement with simulations.