Numerical simulation of the induction heating of a magnesium-alloy round billet

A mathematical model of the transient electro-thermal coupling of the induction heating of a magnesiumalloy round billet is established herein. The heating curve and temperature distribution characteristics of a magnesium alloy were calculated during induction heating under different parameters. Factors such as the number of coil turns and the cooling conditions were analyzed. A method for optimizing the temperature control mode and coil length of the magnesium-alloy round billet is proposed. The length of the coil and corresponding heating mode are determined through the coil length ratio( CLR),which provides a theoretical basis for the optimization of the magnesium-alloy round billet's extrusion.

The Approaches and Software Applied to Determining the Optimal Thermal Network in Heating System

In this paper some shortcmings of a certain of metbods applide in determining the optimal path of thrmal network at present are pointed out.A ratioed method for determining the optimal path of thermal network is given.The software complied by the anthors is introduced.Also is bow to calculate and ndyse a concrete examples.

Predictive Mathematical and Statistical Modeling of the Dynamic Poverty Problem in Burundi: Case of an Innovative Economic Optimization System

The mathematical and statistical modeling of the problem of poverty is a major challenge given Burundi’s economic development. Innovative economic optimization systems are widely needed to face the problem of the dynamic of the poverty in Burundi. The Burundian economy shows an inflation rate of -1.5% in 2018 for the Gross Domestic Product growth real rate of 2.8% in 2016. In this research, the aim is to find a model that contributes to solving the problem of poverty in Burundi. The results of this research fill the knowledge gap in the modeling and optimization of the Burundian economic system. The aim of this model is to solve an optimization problem combining the variables of production, consumption, budget, human resources and available raw materials. Scientific modeling and optimal solving of the poverty problem show the tools for measuring poverty rate and determining various countries’ poverty levels when considering advanced knowledge. In addition, investigating the aspects of poverty will properly orient development aid to developing countries and thus, achieve their objectives of growth and the fight against poverty. This paper provides a new and innovative framework for global scientific research regarding the multiple facets of this problem. An estimate of the poverty rate allows good progress with the theory and optimization methods in measuring the poverty rate and achieving sustainable development goals. By comparing the annual food production and the required annual consumption, there is an imbalance between different types of food. Proteins, minerals and vitamins produced in Burundi are sufficient when considering their consumption as required by the entire Burundian population. This positive contribution for the latter comes from the fact that some cows, goats, fishes, ···, slaughtered in Burundi come from neighboring countries. Real production remains in deficit. The lipids, acids, calcium, fibers and carbohydrates produced in Burundi are insufficient for consumption. This negative contribution proves a Burundian food deficit. It is a decision-making indicator for the design and updating of agricultural policy and implementation programs as well as projects. Investment and economic growth are only possible when food security is mastered. The capital allocated to food investment must be revised upwards. Demographic control is also a relevant indicator to push forward Burundi among the emerging countries in 2040. Meanwhile, better understanding of the determinants of poverty by taking cultural and organizational aspects into account guides managers for poverty reduction projects and programs.

家用空气源热泵热水器微通道冷凝器仿真研究

为提升家用空气源热泵热水器水箱外微通道冷凝器的性能,建立了家用空气源热泵热水器水箱外微通道冷凝器的准稳态模型,实验验证结果显示模型误差能控制在±9%以内。依据模型对微通道冷凝器的换热量、换热系数、压降等性能进行仿真研究。结果发现,微通道冷凝器为四流程时能够减小压降并保证换热量满足需要;关键参数微通道截面的最佳尺寸在1.6~2.6 mm^(2)系统性能最优,同时扁管内微通道数应控制在16~24根。研究结果为家用空气源热泵热水器微通道冷凝器的设计提供借鉴。

连铸切割的在线优化

连铸是将钢水变成钢坯的生产过程,在连铸停浇时,会产生尾坯,尾坯的切割也是连铸切割的组成部分。在满足用户的目标值的前提下,我们尽量让切割损失最小。在合理假设的前提下对连铸切割的合理优化,综合运用EXCEL、MATLAB等多种工具,根据数学中的优化及整数规划知识建立优化模型,从而求出最优解。

新型欧姆加热式反应器强化甲烷蒸汽重整的过程分析和优化

传统甲烷蒸汽重整(SMR)反应器(cSMR反应器)中容易出现较大的径向温度梯度,增加了催化剂积炭失活的风险。提出了一种新型的含内外管欧姆加热蒸汽重整固定床反应器(eSMR反应器),以欧姆加热替代了传统工业反应器的燃烧供热方式。通过二维拟均相固定床反应器模拟,比较了eSMR与cSMR反应器的性能差异,分析了eSMR反应器结构及操作条件对其性能的影响。结果表明,相比于cSMR,eSMR反应器出口的平均甲烷转化率和平均温度分别高出26.6%和121 K,且径向温度分布更加均匀;eSMR反应器的内外管直径之比为0.589时,其径向温度梯度最小;增加入口温度、加热电压和水碳比均会提高eSMR反应器出口的平均甲烷转化率和平均温度,增加入口压力的影响相反。本研究可为欧姆加热蒸汽重整反应器的开发提供一定的借鉴。

日光温室主动蓄放热系统热过程模拟与参数优化研究

为进一步提高日光温室太阳能利用效率,降低加温成本,在当前日光温室主动式水循环蓄放热系统的基础上,构建了系统运行数学模型,利用该模型对系统参数(循环水流量与蓄热水箱体积)进行优化设计。研究结果表明:在兰州地区冬季日光温室生产条件下,当系统循环水流量为0.23 m^(3)·h^(-1),蓄热水箱体积为0.13 m^(3)时,系统性能最优,集、放热效率达到70.62%与98.38%,集/放热单元夜间平均热流密度达到237.84 W·m^(-2)。利用优化后参数,为兰州地区EPS装配式日光温室设计了一套太阳能主动蓄放热加温方案:集放/热单元(高2.05 m,宽1.105 m,厚3 cm)为50个,循环水泵流量为11.5 m^(3)·h^(-1),蓄热水箱体积为6.5 m^(3)。该方案可满足日光温室越冬生产,较优化前节约2个集/放热单元,8.5 m^(3)蓄水池体积,降低了加温成本。

Biomass-fuelled combined heat and power: integration in district heating and thermal-energy storage

Conventional approaches towards energy-system modelling and operation are based upon the system design and performance optimization.In system-design optimization,the thermal or mechanical characteristics of the systems providing for the heat or electricity demands were derived separately without integration with the energy source and without interaction with demand,which results in low-efficiency energy performance.This paper presents a key review on the integration of biomass-powered combined heat and power(BCHP)systems in district-heating systems as well as coupling with thermal-energy storage.In BCHP design,the appropriate sizing of the associated components as part of the district-heating system is very important to provide the optimal dispatch strategy as well as minimized cost and environmental impact while it co-operates with thermal-energy storage.Future strategies for the feasibility,evaluation and integration of biomass-powered energy systems in the context of district systems are also studied.

基于线性规划优化小精细化工企业的生产措施

由于小精细化工企业生产灵活、工艺复杂、对成本和利润控制严格,因此,对生产工艺的优化,就成为小精细化工企业生产措施改进的主要内容之一。文章结合小精细化工企业的生产状况以及在该状况条件下相应的约束因素等,采用运筹学线性规划法构建最优计划数学模型,利用计算软件就具体数据进行求解,得到生产计划的最优解。

计及柔性负荷参与的综合能源系统优化调度

为提高源荷匹配度,平抑负荷波动,该文提出计及需求响应负荷和地源热泵出力的综合能源系统优化调度模型,研究柔性负荷与地源热泵在调度顺序不同的情况下对系统的影响。首先,以系统的经济成本和环境成本最小为目标,建立综合能源系统优化调度模型优化各设备的出力。其次,在考虑新能源机组出力不确定性的基础上,利用地源热泵装置转换效率高的特点改善能源互补能力并使其作为一种可调度资源参与系统的调度。最后,在需求侧将柔性负荷分为可转移、可削减负荷作为可调度资源参与调度,平滑负荷曲线。通过算例分析可得:不考虑可调度资源出力顺序的情况下,能有效提高系统的经济和环境效益以及源荷匹配能力。

基于需求侧用户响应分析的电-气-热综合能源系统低碳经济调度

在低碳经济的背景下,为充分发挥供需双侧的互动潜力,提出一种考虑综合需求响应(IDR)和碳交易的电-气-热综合能源系统(EGH-IES)双层低碳经济调度模型。首先,提出考虑多能负荷自身特性、耦合特性和反弹效应的IDR模型和用户权衡经济效益、响应方式和用能偏好的综合效益模型。基于此,建立上层模型为引入奖惩阶梯型碳交易机制的EGHIES低碳经济调度,下层模型为IDR策略的双层优化调度模型。然后,通过Karush-Kuhn-Tucker(KKT)条件、对偶定理和线性化方法将双层模型转换为混合整数线性规划问题进行求解。最后,算例分析表明,综合考虑碳交易和多元负荷特性能促进供需双侧的联合优化,充分发挥EGH-IES的经济低碳性。

原油热化学两段脱水换热节能工艺研究

原油脱水是原油处理工艺中热能消耗的主要环节之一,也是节能降耗的重要研究方向。利用脱水温度与时间的关系,进行脱水工艺散热损失计算,建立了原油热化学两段脱水能耗数学模型,分析了利用换热器回收高温原油和高温采出水热量的节能效果。结果显示:原油热化学两段脱水工艺可以简化为油气水分离优化和脱水工艺优化相对独立的两个部分;油气水分离设备规格尺寸增加时,散热损失增加,但被加热采出水量和换热损失降低,存在总热量损失最小的规格尺寸;脱水设备存在散热量最大的容积量,高温快速脱水或降低脱水温度、延长脱水时间(增加脱水设备容积)均能够降低脱水散热能耗;换热工艺可以降低脱水加热负荷50%以上,节能效果显著。

基于PID参数优化的高炉加热炉壳温度控制研究

高炉的炉壳是承受极高温度、腐蚀和机械应力的部件,炉壳温度过高或过低都可能导致热应力、脱渣等问题,从而影响高炉的正常运行和寿命。通过有效的炉壳温度控制,可以保护炉壳免受过高温度和腐蚀的侵害,延长高炉的使用寿命,因此提出基于PID参数优化的高炉加热炉壳温度控制方法。利用空气定压比热、加热炉蓄热室通道面积、蓄热体比热容等多个参数确定高炉加热炉能量平衡方程,采用拉氏变换建立高炉加热炉数学模型。以加热炉数学模型为基础,遗传算法通过变异、交叉和复制等操作优化加热炉PID控制器参数。利用参数优化后的PID控制器、功率调整器、FP93导电仪表、加热管以及温度测量仪组成高炉加热炉壳温度控制架构,实现高炉加热炉壳温度控制。实验结果表明,所提方法可准确检测高炉加热炉壳的温度,控制精度以及效率高,高炉加热炉壳温度控制效果好。

Modeling of Rectangular Microchannel Heat Sink with Non-Uniform Channels and Multi-Objective Optimization

Rectangular microchannel heat sinks(MCHS)are widely used to cool high-heat-flux electronic devices.However,previous studies focused mainly on MCHS with uniform channels(UCs).This study considers a microchannel heat sink with non-uniform channels(NUCs).A mathematical model is developed based on energy equations and the Darcy flow principle.Explicit expressions for total thermal resistance and coolant pressure drop are derived using the thermoelectric analogy.Experiments and numerical simulations are performed to verify the mathematical model.As non-uniformity increases,total coolant pressure drop decreases but at the cost of higher thermal resistance.The overall performance of NUCs is better than that of UCs because of their lower ratio of pumping power to cooling power.Heat transfer performance of NUCs changes little for more than 120 channels and depends mainly on channel arrangement.A multi-objective optimization is conducted to minimize the thermal resistance and pumping power of an NUC.An optimal NUC saves 64%pumping power compared with a conventional UC for the total thermal resistance of 0.1℃/W,indicating that the use of non-uniform channels could be very helpful to reduce the flow resistance of MCHS.

高精度钢坯温度预报模型研究及加热炉二级系统开发

为解决加热炉二级系统中钢坯温度预报模型和炉温设定模型功能不能适应现场生产工况变化的问题,开发了全新的加热炉二级过程控制系统,并研发了高精度钢坯温预报模型和炉温设定模型。钢坯温预报模型精度通过黑匣子试验与工业化试验校验得到了验证;炉温设定模型采用分段加权炉温设定和专家经验相结合的方法,实现了炉温的优化设定,解决了复杂生产状况下炉温自动设定这一难题。

基于非线性规划法的船舶浮态计算

提出了利用非线性规划法进行船舶任意倾斜状态下浮态计算的方法,建立了以总复原力臂的绝对值为目标函数,保证排水量等于重量为约束条件,吃水、横倾角及纵倾角为设计变量的优化数学模型.与传统的矩阵方法相比较,该法在每次迭代计算中不需要计算倾斜水线面上的各要素,只需计算倾斜水线面以下的排水体积和浮心坐标,使计算量大大减少.对60000t油船在各种装载状态下浮态的计算,证明了该方法的简便和可靠性.

水合物浆液流动特性研究

采用水合物循环管路装置,添加比例为水量2%(质量比)的防聚剂Span80,在压力为1.6MPa、温度为280.2K的条件下,测定了(柴油+甲烷+四氢呋喃+水)体系在不同水油体积比时生成水合物浆液的流体力学行为。将(水合物+液体)的非均相体系当作拟流体处理,建立了水合物浆液的流动模型,计算了各实验体系的表观粘度,分析了不同水油比时气体消耗量、流量、表观粘度随时间的变化趋势。

基于市场报价的阻塞管理模型及内点法实现

提出了一种电力市场下解决阻塞问题的新方法 ,它可以根据市场报价同时调整实时平衡市场下的发电机出力和削减部分短期双边合同量。建立了阻塞管理的非线性数学模型 ,应用改造的非线性原对偶内点法最优潮流求解以上模型 ,计算出的节点实时电价体现了如何在各用户中分摊阻塞管理费用。算例表明 ,该方法可以根据市场参与者的报价得到最优的调度方案 ,利用节点电价指导用户调整用电计划 ,从而有效地解决了阻塞问题。

地下水源热泵的最优化研究

为了根据不同的使用条件 ,进一步提高地下水源热泵机组的性能 ,通过对机组运行特性的分析 ,依据技术经济优化准则 ,以年度费用总额为目标函数 ,建立系统综合优化数学模型 ,并编制了计算程序。在保证机组安全可靠地满足建筑物冷热负荷需求的前提下 ,根据不同的地下水温度与深度 ,对系统关键运行参数及部件进行了优化选择计算。该方法兼顾了供热供冷运行的可靠性与经济性 ,可实现系统内各部件的最优匹配。与传统设计方法相比 。

基于数字高程模型和数学规划的土地平整工程设计优化

应用数字高程模型(DEM)与数学规划(MP)方法,研究土地平整工程设计中田块的划分、土方量计算和土方量调配的优化方法,为土地平整工程设计提供综合、系统和精确的方法,节约投资费用。该文以南京市江宁区湖熟镇土地平整项目工程为例,采用ArcGIS9.3软件建立大比例尺DEM,划分了土地平整区域和耕作田块,基于DEM计算了现状高程、土方量、土方运输重心,采用数学规划求解了设计高程和土方调配的最优方案。研究表明:该方法合理确定了田块的规模、定量计算了优化设计高程、总土方量比原设计方案减少了9.37%,且制作了最优土方调配路径图。