基于遗传算法的交易中心停车场优化设计

根据某交易中心大型停车场的实际情况 ,并利用大型客车和轿车的长度、宽度、最小转弯半径等数据 ,建立了停车场优化停车设计模型 ,采用遗传算法进行求解 ,得到了停车场的最优停放布局和车位排列角度的优化结果 .本文优化设计的思想、方法和结果对其他大型停车场优化设计也有一定的参考价值 .     

矩形微通道散热器流道的数值模拟及尺寸优化

微通道散热器具有体积小、流速小、压降小、散热高等优点,随着工业微型化的发展,微型散热器的应用越来越广泛.已有的研究表明,微通道的散热性能主要决定于微通道的几何参数和流体的流动情况,相对于三角形和梯形结构,矩形微通道具有更好的散热性能.基于ANSYS Workbench有限元软件,对长度为40 mm,不同截面尺寸的单通道内流体流动及传热性能进行了数值模拟,给出具有较小压降、较大散热效率的微通道尺寸.对优化后的模型计算分析,在一定流体流速和温度的初始状态下,基底给一定热通量,经过计算,散热器可运输的热通量较高,压降较低,热传递效率较大,散热器具有良好的工作性能.     

电渗驱动微通道流中的扩散

利用差分方法对电渗驱动微通道中的脉冲样品的浓度扩散进行了数值模拟,结果说明外加电场和缓冲液浓度对样品的扩散起着重要的作用,而水力直径及其通道的高宽比对扩散的影响甚微．采用减小外加电场和减小缓冲液浓度的办法,可以防止样品带宽的增大、增强检测和分离的效果,同时又保持比较快的输送速度．该结论对于微通道的优化设计具有参考价值．     

功率控制单元板卡布局优化设计研究

功率控制单元是智能配电系统中的关键单元,如何优化功率控制单元板卡的布局,从而保证其稳健的工作是工程应用中关心的重要问题.以功率控制单元为研究对象,依据该单元的设计要求,提出了功率控制单元板卡的优化设计方法.并运用Matlab软件及Lingo软件,以各板卡的功率均匀为优化目标,对具体的功率控制单元中各个板卡上配电通道的布局进行了优化设计,给出了具体的设计方案,从而使板卡的布局更加合理.     

探井布局问题的遗传算法

首先建立探井布局问题的数学模型 .其次基于所建立的数学模型 ,给出了求解探井布局问题的遗传算法 ,并就一个具体问题进行了计算 .计算结果表明 ,用遗传算法求解探井布局问题耗时少 ,适应性好 ,且对于处理大规模的探井布局问题十分有效 .     

基于改进遗传算法的布局优化子问题

本针对子问题，构造了布局子问题(关于同构布局等价类)的改进遗传算法。将该算法应用于二维布局优化子问题，数值实验表明该算法能够在很好地保持图元的邻接关系的前提下找到子问题的最优解。由于布局优化问题可分解为有限个子问题，所以利用该算法可以找到整个布局优化问题的全局最优解。     

水平井筒压降重要性的判别新方法研究

以前许多关于水平井的研究,都没有涉及到井筒压降,通过建立数学模型,提出了简单的解析式,来确定井筒压降对水平井流入的相对影响.用两个无量纲数的简单作用来说明水平井筒中的压降的相对重要性,一个是井筒中流动的雷诺数,另一个是被称为水平井数的新无量纲数.用这一相对关系,优化设计井筒的直径和长度来保证井筒压降不影响产能.     

工程项目资源均衡优化的混合遗传算法研究

"工期固定—资源均衡"优化是指在工期一定的条件下,合理调整网络计划的某些工序,以实现资源均衡利用的一种管理方法.本文基于工程项目资源均衡优化方法中常用的遗传算法和最小矩法,提出了一种混合遗传算法.该算法首先使用遗传算法得到一个较好的初始点,然后采用最小矩法进行局部优化,克服了遗传算法局部寻优能力不足的缺陷,增强了算法的优化效果.最后通过算例分析验证了该混合算法的可行性和有效性,因而是一种较好的优化算法.     

基于嵌入式多项式混沌展开法的随机边界下流动与传热问题不确定性量化

提出了一种嵌入式多项式混沌展开(polynomial chaos expansion, PCE)的随机边界条件下流动与传热问题不确定性量化方法及有限元程序框架.该方法利用Karhunen-Loeve展开表达随机输入边界条件,以及嵌入式多项式混沌展开法表达输出随机场;同时利用谱分解技术将控制方程转化为一组确定性控制方程,并对每个多项式混沌进行求解得到其统计特征.与Monte-Carlo法相比,该方法能够准确高效地预测随机边界条件下流动与传热问题的不确定性特征,同时可以节省大量计算资源.     

基于遗传算法的多通道密集式移动货架订单拣选研究

密集式移动货架越来越多地应用到仓储实践中,提高了仓储空间利用率,但增加了订单拣选的时间成本。本文根据密集式移动货架的仓储布局特点,针对多条通道可同时打开的情况,将货架移动时间转换成通道移动距离进行计算,提出了多条通道依次移动的优化规则,以整批订单拣选所耗费的总时间最少为目标,建立了订单拣选顺序优化的数学模型。针对该模型的特点,设计了实数编码且全局寻优的遗传算法,并进行了不同规模的算例模拟。计算结果表明,该算法具有较强的适用性,针对不同规模的问题,均有显著的优化效果;货架数量、订单数量以及移动通道数量的小幅度增减,将会导致总拣选时间较大幅度的波动;多条移动通道初始位置居于中部或均匀分散,总拣选时间略优于其集中于仓储系统一端。     

热特性参数可变时抛物线型截面环肋传热的最优化研究

肋片传热的最优化的传统处理方法是当执行一定的传热任务时,具有最少的肋片材料消耗(投资).最少重量的冷却肋片是具有抛物线型的截面.本文应用不变嵌入原理研究了当热特性参数可变时抛物线型截面环肋传热的最优几何尺寸,同时还对两个主要的物理参数,即导热系数变化参数α和放热系数变化指数m对最优几何尺寸的影响进行研究.所得结果对工程设计具有现实指导意义.     

Multi-objective optimization of pin fin to determine the optimal fin geometry using genetic algorithm

In this study, one dimensional heat transfer in a pin fin is modeled and optimized. We used Bezier curves to determine the best geometry of the fin. The model equations are solved to analyze the heat transfer. Total heat transfer rate and fin efficiency factor are considered as two objective functions and multi-objective optimization carried out to maximize heat transfer rate and fin efficiency simultaneously. Fast and elitist non-dominated sorting genetic algorithm (NSGA-II) is used to determine a set of multiple optimum solutions, called ‘Pareto optimal solutions. The optimized results are presented with Pareto front which demonstrate conflict between two objective functions in the optimized point, both energy conservation and thermal analysis are carried out to verify the solution method and the results shows good precision.     

A fast running numerical model based on the implementation of volume forces for prediction of pressure drop in a fin tube heat exchanger

Numerical based design of geometrical structures is common when studying systems involving heat exchangers, a central component in several fields, such as industrial, vehicle and household systems. The geometrical structure of heat exchangers is generally comprised by closely placed fins and tube bundles. The creation of a mesh grid for a geometrically compact heat exchanger will result in a dense structure, which is not feasible for personal computer usage. Hence, volume forces were created based on Direct Numerical Simulations (DNS) on a Flow Representative Volume (FRV) of a tube fin heat exchanger in an internal duct system of a heat pump tumble dryer. A relation of the volume averaged velocity and the volume averaged force was established in two different FRV models with a finite element simulation in COMSOL. This relation was subsequently used to create flow resistance coefficients based on volume averaged expressions of fluid velocity and volume forces. These flow resistance coefficients were implemented in two respective porous models, which represent the entire heat exchanger except the interior arrangements of fins and tube bundles. Hence, the computation time was reduced thanks to the absence of a dense mesh grid. Experimental results of the entire heat exchanger showed good agreement with the second porous model in terms of pressure drop and volume flow rate.     

Numerical analysis of convection heat transfer from an array of perforated fins using the Reynolds averaged Navier–Stokes equations and large-eddy simulation method

Extended surfaces (fins) are frequently used in heat exchange devices to increase the heat transfer between a primary surface and the surrounding fluid. In the present study, we determined the thermal performance of an efficient type of perforated fin and we compared the results with those obtained for a simple solid fin and a flat surface without fins in the same working conditions. The modeled geometry comprised fins that had small channels with a circular cross section and different configurations, which were arranged stream-wise along the fin's length. The turbulent flow field around the perforated fins was modeled using the Reynolds averaged Navier–Stokes (RANS) equations and large-eddy simulation (LES) method with a suitable subgrid-scale model. The conjugate differential equations for both the solid and gas phases were solved simultaneously using the finite volume procedure with the SIMPLE algorithm. For LES, the flow and heat transfer characteristics were determined for a Reynolds number equal to 3.2×10⁴ based on the fin length and a Prandtl number of 0.71. The results indicated that among the different configurations, the fins with three openings had the best thermo-hydraulic performance. In addition, we found that although the heat transfer rates predicted by RANS and LES were in close agreement, there were noticeable differences in the important flow characteristics, such as the recirculation zone around the fins and the total drag force on them.     

Application of the two-dimensional differential transform method to heat conduction problem for heat transfer in longitudinal rectangular and convex parabolic fins

In this article, approximate analytical (series) solutions for the temperature distribution in a longitudinal rectangular and convex parabolic fins with temperature dependent thermal conductivity and heat transfer coefficient are derived. The transient heat conduction problem is solved for the first time using the two-dimensional differential transform method (2D DTM). The effects of some physical parameters such as the thermo-geometric parameter, exponent and thermal conductivity gradient on temperature distribution are studied. Furthermore, we study the temperature profile at the fin tip.     

Investigating the effect of various nanoparticle and base liquid types on the nanofluids heat and fluid flow in a microchannel

In this paper, heat transfer and pressure drop of different nanofluid types in a two-dimensional microchannel is investigated numerically. To do this, an Eulerian–Eulerian two-phase model is used for nanofluid simulation and the governing equations are solved using a finite volume method. Nine different nanoparticles and three different base liquid types (water, ethylene glycol and engine oil) are considered. Heat transfer and pressure drop of different nanofluid types are compared at Re = 100 and 1% volume concentration for different nanoparticles and at constant inlet velocity for different base liquids. Numerical results show an almost equal pressure drop for all the nanoparticles dispersed in water, while, the heat transfer coefficient is highest for water–diamond and is the lowest for water–SiO₂ nanofluids. Also, the pressure drop for water-based nanofluid is very lower than the others and the heat transfer coefficient is the highest for water-based nanofluids.     

Mixed convection heat transfer by nanofluids in a cavity with two oscillating flexible fins: A fluid–structure interaction approach

This study investigated the effects of two oscillating fins on the heat transfer rate and flow characteristics of a nanofluid inside a square enclosure. Both fins were attached to the hot wall and both fins oscillated at the same frequencies and amplitudes. The finite element method implemented in the arbitrary Lagrangian–Eulerian (ALE) technique was used to solve the equations describing the interactions and movements of the nanofluid and fins. Comparisons of our results and those reported in previous studies demonstrated that the modeling and numerical investigations were valid and reliable. The results showed that the increase in the heat transfer rate was due to the oscillation of the fins. In addition, the increasing trend in the heat transfer rate due to the oscillating fins decreased as the ratio of the thermal conductivity of the fins relative to the nanofluid increased. Increasing the thermal conductivity and viscosity parameters enhanced and weakened the heat transfer rate, respectively.     

“Disc-point” mass transfer Constructal optimizations with Darcy and Hagen–Poiseuille flows in porous media

Analogizing with Rocha et al.’s [L.A.O. Rocha, S. Lorente, A. Bejan, Int. J. Heat Mass Transfer 45 (8) (2002) 1643–1652] heat conduction model of a disc-shaped body, a “disc-point” mass transfer model with porous media is investigated by using Constructal theory. The heat flow with Fourier law is considered in Rocha et al.’s heat conduction model, while the mass flow with both Darcy law and Hagen–Poiseuille law are considered in the mass transfer model, respectively. The optimal constructs of radial- and branched-pattern discs are obtained by taking maximum pressure drop minimization as optimization objective. The results show that there exist optimal aspect ratios which lead to the minimization of maximum pressure drop of the radial-pattern disc with Darcy flow and Hagen–Poiseuille flow in the channels, respectively. For the first order branched-pattern disc, different definitions of the first order channel fraction lead to different optimization results. When the first order open space fraction is defined as the ratio of the total open space surface area of the whole disc to the whole disc area, there exists an optimal elemental open space fraction which leads to the minimum dimensionless maximum pressure drop of the first order branched-pattern disc. When the product of the cubic of first order open space fraction and the reciprocal of the dimensionless permeability of low permeability porous media is 1000, the critical dimensionless radius, which determines whether the radial- or branched-pattern design is adopted, is 1.78. That is, when the radius of the branched-pattern disc is higher than the critical radius, branched-pattern design should be adopted, otherwise the radial-pattern design should be adopted. The comparison between the optimal constructs of the mass transfer model in this paper and Rocha et al.’s heat conduction model are carried out.     

Topology Optimization of Fins for Rapid Heat Storage and Release in Triangular-Inside Tube Units北大核心CSCD

针对传统相变蓄热器传热速率低的问题,提出了一种内三角管式的蓄热器,并基于拓扑优化原理,以强化换热为目的,对其进行肋片设计,重构了拓扑结果,进而提取其拓扑特征重新设计肋片,分析了不同肋片设计对传热能力的影响。结果表明:内三角管式蓄热器相比传统圆管式蓄热器,蓄放热性能大大提高;安装拓扑重构肋片的蓄热器可以使蓄、放热时间缩短,传热效率提高;在蓄热过程中,分叉的拓扑特征可以提高自然对流作用;在放热过程中,安装拓扑重构肋片的蓄热器(火 积)耗散更小,可逆性更好,换热效率更高。     

Symmetry analysis of a heat conduction model for heat transfer in a longitudinal rectangular fin of a heterogeneous material

We consider a heat conduction model arising in transient heat transfer through longitudinal fins of a heterogeneous (functionally graded) material. In this case, the thermal conductivity depends on the spatial variable. The heat transfer coefficient depends on the temperature and is given by the power law function. The resulting nonlinear partial differential equation is analyzed using both classical and nonclassical symmetry techniques. Both the transient state and the steady state result in a number of exotic symmetries being admitted by the governing equation. Furthermore, nonclassical symmetries are also admitted. Both classical and nonclassical symmetry analysis results in some useful reductions and some remarkable exact solutions are constructed.