Heat distribution model under hydrogen-rich low-carbon conditions in blast furnace

Low carbon development of blast furnaces is one of the key technological directions in the current development of ironmaking.Owing to the differences in the physical and chemical properties of hydrogen and carbon,hydrogen-rich media entering a blast furnace will change the heat distribution,thus affecting the stability of production.Accordingly,a heat distribution model was proposed to study the temperature distribution in a blast furnace,simultaneously considering gas-solid heat exchange,slag and iron melting,and chemical reactions.The model was used to analyze the temperature distribution of a 2300 m^(3) blast furnace and was verified via comparison with actual production data.Subsequently,the effects of the injection rate of hydrogen-rich media,H2 concentration,and oxygen enrichment rate of the blast on the temperature distribution were investigated.Results indicated that the increase in the injection rate of the hydrogen-rich media decreased the amount of direct reduction and led to an increase in the furnace temperature.Furthermore,an increase in the oxygen enrichment rate led to a decrease in the furnace temperature,but could reduce the solid fuel ratio,while the change in H2 concentration had less effect on the temperature distribution.The combination of hydrogen-rich media injection and the increase in the oxygen enrichment rate would help to adjust the temperature distribution to the same level as the conventional blast furnace conditions.

Numerical investigation for effects of natural light and ventilation on 3D tomato body heat distribution in a Venlo greenhouse

Maintaining suitable temperature level around tomato in the greenhouse is essential for the high-quality production.However,in summer,the temperature level around the tomato is usually unclear except using a high-precision temperature imager.To solve this problem,thermal performance of 3D(three-dimensional)tomato model built based on SolidWorks was investigated by the computational fluid dynamics(CFD)simulations.To assess the effect of temperature distribution around the tomato,a simplified 3D tomato numerical model was firstly validated by a set of field measurement data.The light intensity and indoor ventilation were regarded as the mainly environment factors in the Venlo greenhouse,thermal stratification around tomatoes at different time of day was further studied.The numerical results illustrated the different temperature distribution around tomato body under different radiation intensity.It was found that ventilation could obviously adjust the temperature gradient around the tomato,and alleviate high temperature effect particularly in summer.Suitable ventilation could create a suitable thermal environment for the tomato growth.This study clearly demonstrated 3D temperature distribution around tomatoes,which is beneficial to provide the reference for accurate detection of 3D tomato temperature and appropriate thermal environment design.

Spatial Distributions of Atmospheric Radiative Fluxes and Heating Rates over China during Summer

The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the lower atmosphere over central China to be smaller than the fluxes over southern and northern China by generating more clouds. The existence of a larger quantity of clouds over central China reflects a greater amount of solar radiation back into space. The vertical gradients of upward shortwave radiative fluxes in the atmosphere below 8 km are greater than those above 8 km. The latitudinal-altitude distributions of downward longwave radiative fluxes show a slantwise decreasing trend from low latitudes to high latitudes that gradually weaken in the downward direction. The upward longwave radiative fluxes also weaken in the upward direction but with larger gradients. The maximum heating rates by solar radiation and cooling rates by longwave infrared radiation are located over 28 40°N at 7 8 km mean sea level (MSL), and they are larger than the rates in the northern and southern regions. The heating and cooling rates match well both vertically and geographically.

考虑系统故障随机性的电热联合系统备用与DNE分布鲁棒协同优化调度

为实现电热联合系统的安全稳定运行,提高可再生能源消纳,提出考虑系统设备故障随机性的电热联合系统备用与“不超过”(DNE)分布鲁棒协同优化调度模型。首先,以常规机组和热电联产机组运行成本最小为综合优化目标,电功率平衡约束、热功率平衡约束等为约束条件,建立确定性电热联合系统优化调度模型;其次,在综合考虑风电功率、设备故障随机性以及DNE极限基础上建立电热联合系统分布鲁棒优化调度模型;最后,以修改的9节点系统为例,验证了所提模型可有效提高风电消纳率和系统的经济性。

计及可变流量调节模式的电热综合能源系统条件分布鲁棒优化调度

电-热综合能源系统(integrated electricity and heat system,IEHS)可以有效促进可再生能源消纳。构建区域供热系统精细化模型与合理的可再生能源不确定性出力模型是调度IEHS的两个难点。该文首先提出计及可变流量调节模式的IEHS条件分布鲁棒优化调度模型,主要有两点改进:通过构建基于修正模糊集的条件分布鲁棒模型建模可再生能源预测误差与其预测出力信息之间的内在依赖性,提升调度结果安全性与最优性;基于流体能量守恒方程与一阶隐式迎风格式建立可变流量调节模式下的IEHS调度模型,以期充分挖掘区域供热系统的灵活性,促进可再生能源消纳。所构建的IEHS调度模型为含有大量非线性约束的条件分布鲁棒模型,难以直接求解。对此,通过对偶理论与条件风险价值近似方法将条件分布鲁棒模型转化为含非线性约束的确定性模型,并提出自适应McCormick算法用以求解非线性约束。通过不同规模案例仿真表明,所提模型能够降低IEHS的调度成本,所提算法在保证可行性的条件下快速求出问题的近似最优解,最优间隙小于千分之一。

A Cogeneration System for an Apartment Building Based on Distributed Heat Storage Technology

In order for economically viable distributed generation systems for apartment buildings to spread, it is essential to develop an efficient and low-cost heat supply system. We have developed a new eogeneration system called the Neighboring Cogeneration system （NCG）. The key concept of this system is to install a heat accumulator with a hot water supply and a room heating function at each household and to connect different households by a single loop of hot water pipe. As a result, time leveling of the heat supply and heat transferring among households becomes possible. Thus, the costs of the pipe and the heat source equipment decrease. Furthermore, because all of the heat accumulators store heat, the total heat storage capacity is large enough for cogeneration to generate exhaust heat according to the electricity demand and with a high operating rate. In this paper, we report the results of the NCG system for 7 lived-in households. The controlling system worked efficiently. All of the households were able to use hot water without any difficulties. Further, we report the results of the energy saving effect of the NCG system for 50 lived-in households by means of a simulation based on the experimental results for NEXT21.

考虑线路动态电热特性的交直流系统分布鲁棒潮流优化策略

为了充分发挥交直流线路耐热特性、提高系统在不确定运行环境下应对故障的调控能力,以含柔性直流输电技术(VSC-HVDC)的交直流系统为研究对象,提出一种考虑线路动态电热特性的分布鲁棒潮流优化策略。首先,根据热传导理论分别建立交流架空线路、直流电缆线路的动态电热模型,而后在校正控制中引入交、直流输电线路短期最高允许温度(SAOT)约束及校正期间最大热积累量来代替长期允许温度(LAOT)作为在校正期间的暂时安全约束,以达到充分利用线路的短期过载/耐热特性的目的;其次,将故障后的校正过程划分成两个子校正过程,通过最大化储能及VSC-HVDC的快速校正能力,弥补常规调控装置难以快速响应指令的缺陷,进一步,在基于Kullback-Leibler(KL)散度所构建的风荷概率分布模糊集上,通过在考虑风荷最恶劣概率分布的情况下进行潮流优化,改善了传统鲁棒优化方法过于保守的问题;再次,在列和约束生成(C&CG)算法和Multi-cut Benders分解算法的基础上,提出一种融合物理知识的双循环分解算法,不仅能避免对非过载线路热平衡方程的线性化,同时还能避免多场景多故障协同求解;最后,在基于改进的IEEE 39测试系统中对所提模型及算法的有效性进行了验证。

Temperature field model in surface grinding: a comparative assessment

Grinding is a crucial process in machining workpieces because it plays a vital role in achieving the desired precision and surface quality.However,a significant technical challenge in grinding is the potential increase in temperature due to high specific energy,which can lead to surface thermal damage.Therefore,ensuring control over the surface integrity of workpieces during grinding becomes a critical concern.This necessitates the development of temperature field models that consider various parameters,such as workpiece materials,grinding wheels,grinding parameters,cooling methods,and media,to guide industrial production.This study thoroughly analyzes and summarizes grinding temperature field models.First,the theory of the grinding temperature field is investigated,classifying it into traditional models based on a continuous belt heat source and those based on a discrete heat source,depending on whether the heat source is uniform and continuous.Through this examination,a more accurate grinding temperature model that closely aligns with practical grinding conditions is derived.Subsequently,various grinding thermal models are summarized,including models for the heat source distribution,energy distribution proportional coefficient,and convective heat transfer coefficient.Through comprehensive research,the most widely recognized,utilized,and accurate model for each category is identified.The application of these grinding thermal models is reviewed,shedding light on the governing laws that dictate the influence of the heat source distribution,heat distribution,and convective heat transfer in the grinding arc zone on the grinding temperature field.Finally,considering the current issues in the field of grinding temperature,potential future research directions are proposed.The aim of this study is to provide theoretical guidance and technical support for predicting workpiece temperature and improving surface integrity.

Effects of thermal transport properties on temperature distribution within silicon wafer

A combined conduction and radiation heat transfer model was used to simulate the heat transfer within wafer and investigate the effect of thermal transport properties on temperature non-uniformity within wafer surface. It is found that the increased conductivities in both doped and undoped regions help reduce the temperature difference across the wafer surface. However, the doped layer conductivity has little effect on the overall temperature distribution and difference. The temperature level and difference on the top surface drop suddenly when absorption coefficient changes from 104 to 103 m-1. When the absorption coefficient is less or equal to 103 m-1, the temperature level and difference do not change much. The emissivity has the dominant effect on the top surface temperature level and difference. Higher surface emissivity can easily increase the temperature level of the wafer surface. After using the improved property data, the overall temperature level reduces by about 200 K from the basis case. The results will help improve the current understanding of the energy transport in the rapid thermal processing and the wafer temperature monitor and control level.

A code-independent technique for computational verification of fluid mechanics and heat transfer problems

The goal of this paper is to present a versatile framework for solution verification of PDE＇s. We first generalize the Richardson Extrapolation technique to an optimized extrapolation solution procedure that constructs the best consistent solution from a set of two or three coarse grid solution in the discrete norm of choice. This technique generalizes the Least Square Extrapolation method introduced by one of the author and W. Shyy. We second establish the conditioning number of the problem in a reduced space that approximates the main feature of the numerical solution thanks to a sensitivity analysis. Overall our method produces an a posteriori error estimation in this reduced space of approximation. The key feature of our method is that our construction does not require an internal knowledge of the software neither the source code that produces the solution to be verified. It can be applied in principle as a postprocessing procedure to off the shelf commercial code. We demonstrate the robustness of our method with two steady problems that are separately an incompressible back step flow test case and a heat transfer problem for a battery. Our error estimate might be ultimately verified with a near by manufactured solution. While our pro- cedure is systematic and requires numerous computation of residuals, one can take advantage of distributed computing to get quickly the error estimate.

Comparison of Temperature Field Distribution between Cement Preclinkering Technology and Cement Precalcining Technology

Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology,we studied the characteristics of temperature field distribution of cement preclinkering technology systems including cyclone preheater,preclinkering furnace,and rotary kiln.We used numericalsimulation method to obtain data of temperature field distribution.Some results are found by system study.The ratio of tailcoalof cement preclinkering technology is about 70%,and raw mealtemperature can reach 1070 ℃.Shorter L/D kiln type of preclinkering technology can obtain more stable calcining zone temperature.The highest solid temperature of cement preclinkering technology is higher than 80 ℃,and high temperature region（〉1450 ℃）length is 2 times,which is beneficialfor calcining clinker and higher clinker quality.So cement preclinkering technology can obtain more performance temperature filed,which improves both the solid-phase reaction and liquid-phase reaction.

考虑单峰分布的电热综合能源系统风险调度

不确定可再生能源并入电热综合能源系统后将引发系统运行风险,而通过合理量化风险,实现风险可控性和调度经济性平衡是电热综合能源系统风险调度的关键。依据随机风电功率的单峰分布特性构建矩模糊集并以此刻画风电功率的不确定性,同时采用分布鲁棒机会约束方法来刻画系统的运行风险,进而建立了电热综合能源系统的分布鲁棒风险调度模型。在此基础上,从风险发生概率和经济成本的角度,提出了评估不确定风电功率引发运行风险的量化指标:均值风险概率和风险调度成本。最后,以改进的巴厘岛电热综合能源系统为例进行算例分析,验证了所提模型及其风险评估指标的可行性和有效性,并给出了电热综合能源系统的最优调度决策。

计及热惯性的热电联产虚拟电厂韧性提升策略

日益频繁的极端天气给电热耦合系统造成的影响愈发严重。韧性是衡量系统抵御极端事件、减少故障影响并快速恢复的核心指标。为提升电热耦合系统抵御极端灾害的能力,提出一种考虑热惯性的热电联产虚拟电厂(combined heat and power-virtual power plant,CHP-VPP)两阶段三层韧性提升策略。第一阶段以联络开关成本最小为目标,基于最小生成树理论对系统进行重构;第二阶段以运行成本最小为目标,基于分布鲁棒优化理论制定最恶劣的故障场景下的最优决策。采用列与约束生成算法进行迭代求解。基于IEEE 33节点电力系统+6节点供热系统构建CHP-VPP测试系统,仿真结果表明,所提出的方法可有效提升CHP-VPP应对极端灾害的韧性。

基于分布鲁棒的风-氢混合系统氢储能容量优化配置

氢储能系统受地理、气候条件限制较小,在构建面向高比例新能源电力系统的风-储混合系统中极具发展潜力。然而,由于风电场的出力具有不确定性,氢储能系统需要在储能、释能、热备用等工况下频繁切换,内部热能供需平衡也呈现出不确定性,进而影响其响应速度甚至实际可用容量。为此,设计了考虑热平衡的风-氢混合系统,构建了考虑电解槽、燃料电池间歇工作模式热平衡的氢储能系统模型;在此基础上,综合考虑风电场功率的不确定性和氢储能系统的投资成本,提出了考虑热平衡不确定性的风-氢混合系统氢储能容量优化配置方法。采用分布鲁棒方法对风电场功率的不确定性进行建模,并将其转化为一组线性风险机会约束进行求解。基于实际风电场数据构建算例,对所提模型和方法进行验证和分析。结果表明,氢储能系统中电解槽和燃料电池的散热系数对系统实际可用容量具有重要的影响,在风-氢混合系统的氢储能容量配置中考虑热平衡约束可以有效提升氢储能系统的实际可用容量和混合系统的经济性。

考虑氢储能热平衡的风-氢混合系统优化调度方法

风-氢混合系统(W-HHS)参与电网调度时,氢储能系统(HESS)间歇工作的热能需求特性成为影响系统调度的关键因素。建立了具备余热利用系统的HESS模型,在HESS热量平衡和热功率平衡约束下,提出了以提高W-HHS运行收益为目标,满足混合系统输出功率跟踪电网调度曲线约束的W-HHS优化调度方法。最后,通过青海风电场数据对所提方法和模型进行了验证和分析。结果表明,HESS热平衡约束对W-HHS运行调度具有重要影响,所提方法能提高W-HHS运行的可靠性。参数分析说明,减小散热系数能够降低热平衡约束对W-HHS调度策略的影响,提高风电场并网功率。

基于分布鲁棒优化的电–气–热综合能源系统日前经济调度

风电等可再生能源的出力具有不确定性,传统的鲁棒优化和随机优化方法在处理风电等可再生能源出力不确定性时都存在一些局限与不足。基于分布鲁棒优化研究了考虑风电出力不确定性的电-气-热综合能源系统(electricity-gas-heat integrated energy system,EGH-IES)日前经济调度问题。将Kullback-Leibler(KL)散度作为分布函数与参考分布之间距离的量度,建立风电出力的分布函数集合。然后以系统运行总成本作为目标函数,建立了EGH-IES日前经济调度鲁棒机会约束优化模型。将所建立的鲁棒机会约束优化模型转化为利用求解器可直接求解的确定性混合整数线性优化模型。最后,通过算例分析验证了所提方法的有效性,并分析了电转气技术和热网管道输送延时对风电消纳的作用。

Collaborative Planning of Distributed Wind Power Generation and Distribution Network with Large-scale Heat Pumps

With the advancement of clean heating projects and the integration of large-scale distributed heat pumps into rural distribution networks in northern China,power grid companies face tremendous pressure to invest in power grid upgrades,which bring opportunities for renewable power generation integration.The combination of heating by distributed renewable energy with the flexible operation of heat pumps is a feasible alternative for dealing with grid reinforcement challenges resulting from heating electrification.In this paper,a mathematical model of the collaborative planning of distributed wind power generation(DWPG)and distribution network with large-scale heat pumps is developed.In this model,the operational flexibility of the heat pump load is fully considered and the requirements of a comfortable indoor temperature are met.By applying this model,the goals of not only increasing the profit of DWPG but also reducing the cost of the power grid upgrade can be achieved.

Computational analysis of the flow of pseudoplastic power-law fluids in a microchannel plate

The flow of pseudoplastic power-law fluids with different flow indexes at a microchannel plate was studied using computational fluid dynamic simulation.The velocity distribution along the microchannel plate and especially in the microchannel slits,flow pattern along the outlet arc and the pressure drop through the whole of microchannel plate were investigated at different power-law flow indexes.The results showed that the velocity profile in the microchannel slits for low flow index fluids was similar to the plug flow and had uniform pattern.Also the power-law fluids with lower flow indexes had lower stagnation zones near the outlet of the microchannel plate.The pressure drop through the microchannel plate showed huge differences between the fluids.The most interesting result was that the pressure drops for power-law fluids were very smaller than that of Newtonian fluids.In addition,the heat transfer of the fluids through the microchannel with different channel numbers in a wide range of Reynolds number was investigated.For power-law fluid with flow index(n=0.4),the Nusselt number increases continuously as the number of channels increases.The results highlight the potential use of using pseudoplastic fluids in the microheat exchangers which can lower the pressure drop and increase the heat transfer efficiency.

考虑相变储能与建筑蓄能特性的微网分布鲁棒优化调度

基于相变材料特性建立相变储能水箱热力学模型;分析建筑负荷特性,建立建筑室内温度动态模型;运用基于Wasserstein距离的分布鲁棒算法,建立风电预测误差不确定集。提出考虑相变储能与建筑蓄能特性的微网两阶段分布鲁棒优化调度模型。模型第1阶段是基于风电预测信息,制定日前调度计划,第2阶段考虑风电预测误差,在最恶劣概率分布条件下,获得日内调度计划。最后,运用算例分析相变储能水箱与建筑蓄能特性对风电消纳以及系统调度的影响,并验证分布鲁棒模型的有效性。

市场环境下考虑多元不确定性的热电联合虚拟电厂竞标策略

“双碳”背景下,热电联合虚拟电厂将热电联产机组、储能设施等聚合为可控集合体以促进新能源消纳,具有广阔的发展空间。电力市场环境下,热电联合虚拟电厂的竞标策略决定了其在市场中的购售电量,对其收益具有重要影响。然而,电价和分布式新能源出力等多元不确定性的存在,给热电联合虚拟电厂竞标策略的制定带来困难。为此,提出了市场环境下考虑多元不确定性的热电联合虚拟电厂竞标策略。考虑电价与虚拟电厂内部风光的不确定性,建立热电联合虚拟电厂参与电力市场的竞标模型。利用蒙特卡洛法和后向场景缩减法,构建刻画电价不确定性的典型场景。基于此,结合随机优化方法与基于Wasserstein距离的分布鲁棒方法,将热电联合虚拟电厂竞标模型转换为分布鲁棒随机优化模型,并利用对偶转换和数据驱动方法将该模型转换为单层模型,以利于求解。最后,通过IEEE 30节点系统验证所提方法的有效性。