【作者】 李孟寻；

【导师】 许明田；

【作者基本信息】 山东大学 ， 工程热物理， 2010， 硕士

【摘要】 换热器在众多高能耗工业领域中具有广泛的应用,同时和能量的节约、转换、回收以及新能源的开发都有着密切的联系。通过优化设计提高换热器的性能,减少换热过程热量的不可逆耗散,是提高能源利用率的重要措施,在能源日益短缺和环境污染逐步恶化的今天具有重要的意义。本文将致力于单目标和多目标管壳式换热器优化设计的研究。换热器优化设计的关键问题是选择一个合适的优化目标函数。本文首先以无量纲化的总火积耗散(总火积耗散数)为目标函数,以换热器的一些几何参数和冷流体的出口温度为设计变量,以容许压降和换热器设计标准要求为约束条件,形成了换热器的优化设计问题,并应用遗传算法求解了相应的优化问题。通过比较优化前后的设计方案,发现通过优化设计,在提高换热器有效度的同时,明显减少了泵功的消耗。通过和其它换热器优化设计方法(譬如传统的最小成本法)对比,发现以总火积耗散数为目标函数的换热器优化设计方法在提高换热器性能和减少能量的损耗方面具有明显的优势。但以总火积耗散数为目标函数的单目标换热器优化设计方法存在一定缺陷,即对于以液体为换热介质的换热器,有限温差导热引起的火积耗散远大于流动阻力引起的火积耗散,以二者的和作为目标函数进行单目标优化设计时很容易忽略流动阻力因素的影响。为了解决这一问题,本文以有限温差导热引起的火积耗散数和流体阻力引起的火积耗散数为两个独立的目标函数,应用多目标遗传算法构造了换热器的多目标优化设计方法。通过分析多目标优化过程中换热器性能参数的变化,以及对多目标和单目标优化结果之间的比较,我们发现换热器的多目标优化设计方法具有更大的优势。更多还原

【Abstract】 Heat exchangers are widely applied in high energy consumption industries and are closely related to the energy saving, conversion, recovery as well as the exploitation of new energy sources. To improve the performance of heat exchanger and reduce the irreversible loses occurring in the heat exchange process by optimizing the heat exchanger design is one of important ways to increase the energy efficiency and is of great importance under the current situation that the energy shortage and environment deterioration becomes more and more severe. In the present work, the single-or multi-objective optimization of shell-and-tube heat exchanger design is investigated.The key problem for heat exchanger optimization design is to choose an appropriate objective function. In our work, the total dimensionless entransy dissipation (called as entransy dissipation number) is taken as the objective function, some geometric parameters of the heat exchanger and the outlet temperature of cold fluid are set to the design variables, the admissible pressure drop and requirements of heat exchanger design standard are selected as the constraint conditions, thus an optimization design problem for heat exchanger is formulated. The genetic algorithm is employed to solve the related optimization problems. The comparison between the initial and optimized design plans shows that the optimization process improves the exchanger effectiveness and in the same time reduces the pumping power significantly. In comparison with other optimization approaches, such as the traditional cost-minimization method, the single-objective heat exchanger optimization design method with the entransy dissipation number as the objective function demonstrates obvious advantages on improving the heat exchanger performance and reducing the irreversible loses.However, there exists a drawback for the single-objective heat exchanger optimization design method with the total entransy dissipation number as the objective function, namely, the entransy dissipation induced by heat conduction under finite temperature difference is much larger than that caused by fluid friction in the heat exchange process with fluid as the heat transfer medium. Therefore, the single-objective heat exchanger optimization design method usually neglects the contribution of fluid friction to the entransy dissipation. In order to solve this problem, the entransy dissipation numbers related to the heat conduction and fluid frictions are set to two separate objective functions, a multi-objective optimization of heat exchanger design is proposed with the help of the genetic algorithm. By the analysis of the heat exchanger performance and the comparison with the results of single-objective optimization design, it is found that the multi-objective optimization of heat exchanger design is more advantageous.更多还原