Optimal design and analysis of mechanical draft cooling tower using improved Jaya algorithm

A cooling tower is an imperative component of industrial plants. The minimization of energy related expenses is critical for conservation of resources and energy savings. Hence, the present study explores the use of an improved Jaya algorithm called self-adaptive Jaya algorithm for optimal design of cooling tower from economic facets. In this work, six different examples are considered in the design optimization of mechanical draft cooling tower. Various researchers have attempted the same mathematical models by using different methods like Merkel method, Poppe method and artificial bee colony (ABC) algorithm. The results achieved by using the proposed self-adaptive Jaya algorithm are compared with the results achieved by using the Merkel method, Poppe method, ABC algorithm and basic Jaya algorithm. The proposed self-adaptive Jaya algorithm determines the population size automatically and the user need not tune the population size. The proposed self-adaptive Jaya algorithm is proved better as compared to the other optimization methods with respect to achieving the optimal value of the objective function at less computational effort.     

夏热冬冷地区居住建筑冷热源经济性分析

采用改进的温频法进行负荷计算,针对夏热冬冷地区某居住建筑的冷热源方案进行全寿命周期经济性分析。结果表明,采用地源热泵方案经济性最好,比空气源热泵节省费用约7.5%,比冷水机组加燃气锅炉方案节省费用约21.2%。同时,输配能耗占总能耗比重约20%,应优化设计输配系统,降低输配能耗。采用地源热泵方案时,如能采用与冷却塔的复合运行模式,其运行能耗将进一步降低。     

考虑动态需求的生鲜商品物流配送优化方法研究

目的 针对生鲜商品配送过程中客户需求的变化,协调静态与动态客户需求之间的关系,合理规划路径,并降低物流总成本。方法 首先考虑客户生鲜需求的多样化温控区间、随机订单请求时间及动态需求量等因素,构建物流总成本最小化的整数规划模型。然后,设计基于高斯混合聚类的改进蚁群算法求解该模型,并提出动态需求处理策略,用于路径的再优化。其次,通过与粒子群算法、遗传算法和鲸鱼优化算法进行对比分析,验证文中设计算法的有效性。最后,以重庆市某生鲜配送网络为例,对比分析优化前后的运营指标,并探讨生鲜商品价值损失水平与物流总成本之间的关系。结果 经优化后,物流总成本下降了22.35%,其中惩罚成本、价值损失、配送成本和温控成本分别下降了39.84%、61.84%、29.80%、57.00%。结论 文中所提的模型、算法和动态需求处理策略可以合理规划配送路径,有效降低了总成本,为考虑动态需求的生鲜配送网络优化提供了参考。     

空调用闭式冷却塔的运行参数对其冷却性能的影响

建立了闭式冷却塔热质交换的数学模型，利用该模型并结合计算机编程对闭式冷却塔的冷却性能进行了计算机仿真。系统地研究了喷淋水量、空气湿球温度、空气流量、管内水流量对闭式冷却塔冷却性能的影响趋势，通过分析得到了一些有价值的结论，为闭式冷却塔的研制及优化运行提供了参考依据。     

盘管复合填料型闭式冷却塔性能分析

本文介绍了闭式冷却塔的原理与分类,并归纳总结出简要数学模型。提供了一种测试方法,并用该方法测试分析填料冷却性能以及填料对闭式冷却塔性能的影响,用最小二乘法得到填料特性数N′=0.8λ0.9,并绘制出相关曲线,得出在闭式冷却塔中增加填料可以强化冷却性能。针对放置在不同位置的填料对闭式冷却塔性能影响进行了理论分析,得出闭式冷却塔中填料放置在盘管的上方比放置在盘管下方冷却性能更好。     

Integrated scheduling and tool management in flexible manufacturing systems

A multistage algorithm is proposed that will solve the scheduling problem in a flexible manufacturing system by considering the interrelated subproblems of processing time control, tool allocation and machining conditions optimization. The main objective of the proposed algorithm is to minimize total production cost consisting of tooling, operational and tardiness costs. The proposed integrated approach recognizes an important trade-off in automated manufacturing systems that has been largely unrecognized, and which is believed can be effectively exploited to improve production efficiency and lead to substantial cost reductions.     

Multi-objective optimization of a cooling tower assisted vapor compression refrigeration system

A cooling tower assisted vapor compression refrigeration machine has been considered for optimization with multiple criteria. Two objective functions including the total exergy destruction of the system (as a thermodynamic criterion) and the total product cost of the system (as an economic criterion), have been considered simultaneously. A thermodynamic model based on energy and exergy analyses and an economic model according to the Total Revenue Requirement (TRR) method have been developed. Three optimized systems including a single-objective thermodynamic optimized, a single-objective economic optimized and a multi-objective optimized are obtained. In the case of multi-objective optimization, an example of decision-making process for selection of the final solution from the Pareto frontier has been presented. The exergetic and economic results obtained for three optimized systems have been compared and discussed. The results have shown that the multi-objective design more acceptably satisfies generalized engineering criteria than other two single-objective optimized designs.     

冷却塔补水成本的一种分析方法

本文提出了将集中空调系统冷却塔补水量换算成同等电费的电量来参与空调系统运行能耗成本计算的思路,提出了水的电当量概念。通过对比全国部分城市的水价,发现各城市之间水价差异大,认为在选择空调方案时,应充分重视冷却塔补水的运行成本。     

空调系统冷却塔补水量的估算

本文结合公共建筑单位面积空调冷负荷与冷却塔补水量估算公式,整理了一套中央空调系统的冷却塔补水量的估算方法,推算出几类常见公共建筑的冷却塔单位面积补水量指标,分析其在建筑总用水量中的比例,有助于快速估算建筑总用水量。     

Multi-objective optimization of space station logistics strategies using physical programming

This study extends a previously proposed single-objective optimization formulation of space station logistics strategies to multi-objective optimization. The four-objective model seeks to maximize the mean utilization capacity index, total utilization capacity index, logistics robustness index and flight independency index, aiming to improve both the utilization benefit and the operational robustness of a space station operational scenario. Physical programming is employed to convert the four-objective optimization problem into a single-objective problem. A genetic algorithm is proposed to solve the resulting physical programming-based optimization problem. Moreover, the non-dominated sorting genetic algorithm-II is tested to obtain the Pareto-optimal solution set and verify the Pareto optimality of the physical programming-based solution. The proposed approach is demonstrated with a notional one-year scenario of China's future space station. It is shown that the designer-preferred compromise solution improving both the utilization benefit and the operational robustness is successfully obtained.     

闭式冷却塔性能优化

本文通过对某一公司的闭式冷却塔为例,陈述影响冷却塔性能因素,并进一步着重阐述了冷却塔优化模型的一般步骤,运用数值计算方法分析在各种工况下冷却塔所能达到的最佳性能,并找到最优化设计参数。     

Effect of creep lifetime on geometric optimization of boiler tubes for thermal power plants

In this study, thermomechanical and creep analyses of boiler tubes are performed and a procedure for cost-based optimization of boiler tube geometries is presented. First, analytical thermal convection and conduction heat transfer under ultra-supercritical (USC) and advanced ultra-supercritical (A-USC) conditions as well as numerical evolution of creep stresses in the boiler tube are obtained. Subsequently, the results are used to calculate the thermal efficiency and creep lifetime of austenitic stainless steel Super 304H and Ni-based alloy Nimonic alloy 80A. The geometric parameters of the boiler tube are then optimized to minimize the total cost related to the boiler tubes including capital investment and operational costs. Comparing with the conventional approach which assumes a fixed creep lifetime for simplicity, the present results also showed that creep lifetime assessment is important and should be included in the optimization. This optimization procedure can also be applied to other boiler tube materials under various operating conditions of thermal power plants.     

Integrating reliability optimization into chemical process synthesis

The growing need to achieve high availability for large integrated chemical process systems demands higher levels of system reliability at the operational stage. In these circumstances, it has become critical to consider the reliability aspects of a system and its components at the design stage. Traditional reliability/availability analysis methods and maintenance optimization frameworks, commonly applied at the design stage, are limited in their application, as in most of these methods the designer is required to specify the process system components, their connectivity and their reliabilities a priori. As a result, these traditional methods do not provide the flexibility to reconfigure a process or select initial reliabilities of equipment in a way that maximizes the inherent plant availability at the design stage. In this paper, we developed an optimization framework by combining the reliability optimization and process synthesis challenges and the combined optimization problem is posed as a mixed integer non-linear programming optimization problem. The proposed optimization framework features an expected profit objective function, which takes into account the trade-off between initial capital investment and the annual operational costs by supporting appropriate estimation of revenues, investment cost, raw material and utilities cost, and maintenance cost as a function of the system and its component availability. The effectiveness and usefulness of the proposed optimization framework is demonstrated for the synthesis of the hydrodealkylation process (HDA) process.     

大型冷却塔风荷载的数值模拟研究

针对单体和双塔情况下冷却塔的风荷载进行CFD数值模拟计算,获得冷却塔表面的压力系数。单个冷却塔CFD模拟的结果与规范数据比较接近,说明CFD方法的准确性,同时也发现一些偏差,并对偏差产生的原因进行分析。研究了因雷诺数不同而导致的单塔缩尺效应,发现实尺和缩尺模型的计算结果在最大正压和平台区有差别。分析双塔之间的干扰作用,针对不同风向角可分为尾流直接作用、尾流和临近干扰共同作用、临近干扰作用三个区域。     

Maintenance policies with two-dimensional warranty

A new maintenance policy which minimizes the total expected servicing cost for an item with two-dimensional warranty is proposed. An iterative procedure to estimate the item's failure rate function from historical observations and an optimization algorithm based on Monte Carlo simulation are applied to obtain the best maintenance policy. Numerical examples and sensitivity analysis are presented.     

云环境下大规模定制中资源配置研究

针对传统大规模定制生产模式无法满足日益个性化的产品市场变化,导致产品无法形成生产批量,在生产过程中增加成本和时间的问题,结合云制造的背景环境,提出云环境下大规模定制产品的生产模式,并通过建立包含生产总时间、生产总成本和产品总质量的多目标优化函数模型,使用NSGA-Ⅱ算法对所建模型进行求解,对模式运行中的资源配置问题进行研究。最后通过航模发动机进行算例验证,证明所建模型可以得到解决云环境下大规模定制产品生产过程中资源优化配置问题的最优生产方案。     

基于改进人工鱼群算法的输电塔塔腿拓扑优化

为了解决输电塔塔腿的优化问题,提出了基于改进人工鱼群算法的拓扑优化方法。建立了输电塔结构拓扑优化的计算模型,采用罚函数形式确定了人工鱼群算法的目标函数,并提出了拓扑变量的判定规则。采用人工鱼群算法对输电塔塔腿进行了拓扑优化研究。考虑到基本人工鱼群算法易陷入局部优化解,提出了视野和步长的变化策略,以及觅食行为的加速策略。数值算例结果表明,采用基本人工鱼群算法可以较好的优化输电塔塔腿,而在此基础上利用改进人工鱼群算法可以更有效地优化输电塔塔腿,并且其优化效率明显优化基本人工鱼群算法和差商算法。     

Spreadsheet modeling of optimal maintenance schedule for components in wear-out phase

This paper addresses a method for determining the optimum maintenance schedule for components in the wear-out phase. The interval between maintenance for the components is optimized by minimizing the total cost. This consists of maintenance cost, operational cost, downtime cost and penalty cost. A decision to replace a component must also be taken when a component cannot attain the minimum reliability and availability index requirement. Premium solver platform, a spreadsheet-modeling tool, is utilized to model the optimization problem. Constraints, which are the considerations to be fulfilled, become the director of this process. A minimum and a maximum value are set on each constraint so as to give the working area of the optimization process. The optimization process investigates n-equally spaced maintenance at an interval of Tr. The increase in operational and maintenance costs due to the deterioration of the components is taken into account. This paper also performs a case study and sensitivity analysis on a liquid ring primer of a ship's bilge system.     

Simulation of Cooling of Water Droplet and Film Flows in Large Natural Wet Cooling Towers

An iterational algorithm for calculation of evaporative cooling of water droplets and films in a cooling tower is proposed. It is found from a comparison of results of theoretical calculation and experimental data that the effective radius of the droplets is approximately equal to 3·10^–4 m. The contribution of film cooling is shown to constitute at least 70% of the overall temperature decrease of cooled water in the cooling tower.     

毛细管网在闭式冷却塔中的应用分析

为解决闭式冷却塔在冬天停机时排水不尽易冻裂和遇腐蚀性工质易损坏的问题,将工程塑料毛细管网技术引入闭式冷却塔。根据理论计算设计了毛细管网闭式冷却塔,并且进行了实物模块的性能试验。研究表明：在单台塔体大小相同的条件下,两台毛细管网闭式冷却塔能够达到一台常规管径紫铜管闭式冷却塔的散热能力,且换热器部分的成本相差无几,由于毛细管网闭式冷却塔具有防腐、抗冻、阻垢、降噪的优势,所以具有良好的技术经济性。