【作者】 赵亮；

【导师】 尹洪超；

【作者基本信息】 大连理工大学 ， 热能工程， 2013， 博士

【摘要】 换热网络优化综合和改造同属于过程系统工程的重要领域,对于提高过程工业能量利用率具有重要的作用。经过近半个世纪的发展,各种换热网络优化综合和改造方法相继提出,该领域的研究已初具规模,研究成果广泛应用于实际过程工业系统,并创造了可观的节能效益。近年来,特别是1990年后,随着能源价格的上涨和节能工作越来越受到重视,对换热网络优化改造的研究也越来越受到关注,成为国内外学者近年来最感兴趣的热点研究方向之一。如何建立一套更加可靠有效、符合实际的换热网络优化改造方法,克服以往研究所做的简化假设以及复杂的优化求解代价,已成为提高整个过程工业系统尤其是能量回收子系统能量利用效率的亟待解决问题。本文主要围绕建立考虑多因素影响的换热网络优化改造方法的主题,借助同步优化改造数学规划法展开研究。1、建立换热网络优化改造数学模型。对Yee和Grossman提出的换热网络优化综合分级超结构进行了改进,增加了对于现有换热匹配、增加现有换热匹配换热面积和重新配置现有换热匹配等换热网络优化改造问题所特有的改造措施的描述,去除了等温混合的简化假设,构建了基于分级超结构的换热网络优化改造MINLP数学模型。2、考虑压降的换热网络优化改造方法研究。对本文所建立的换热网络优化改造模型增加压降因素的考虑,结合压降计算模型对换热网络优化改造模型进行了进一步扩展,提出了考虑压降因素的换热网络优化改造方法,同时权衡压降与换热网络改造结构调整对改造优化目标的影响,采用了外层换热网络结构优化和内层操作参数优化的双层求解策略,结合二进制遗传算法和GA/PSO混合算法对模型进行了求解。通过研究实例的优化改造结果验证了所提出的考虑压降的换热网络优化改造方法可以有效避免不考虑压降所出现的各项费用失衡情况和改造方案的不合理性,在换热网络改造中能够有效识别控制压降的关键改造影响因素,获得相比其他文献更好的优化改造结果。3、考虑强化传热的换热网络优化改造方法研究。对本文所建立的换热网络优化改造模型增加强化传热因素的考虑,结合现有成熟的强化传热技术及其对换热网络改造过程中换热设备总传热系数和新增换热面积的影响,对换热网络优化改造模型进行了进一步扩展,提出了考虑强化传热因素的换热网络优化改造方法,综合权衡强化传热投资成本、换热网络结构调整投资成本和运行费用的关系。通过研究实例的优化改造结果验证了所提出的考虑强化传热的换热网络优化改造方法可以合理的判断强化传热的关键应用部位,即使在换热网络结构接近最优时,仍可以通过采用强化传热措施减少所需增加的换热面积,降低改造投资成本,缩短投资回收期,从而获得更加优化的换热网络改造方案。4、考虑强化传热压降控制的换热网络优化改造方法研究。基于本文对于分别考虑压降和强化传热的换热网络优化改造方法的研究,针对强化传热所带来的压降增加所造成的换热网络优化结构偏离真正的最优结果,导致改造方案不合理的问题,给出了从换热网络改造系统建模角度控制强化传热压降问题的考虑强化传热压降控制的换热网络优化改造模型,并结合具体的换热网络优化改造工程实例从换热设备角度探讨了改变换热设备几何结构控制强化传热压降的方法。研究实例表明,改变换热设备几何结构可有效降低强化传热所增加的压降,在改变换热设备几何结构控制强化传热压降的方法中,改变壳体布置和使用螺旋折流板在减缓壳侧压降升高方面比较有效；改变壳体布置和减少管程数目在降低管侧压降方面比较有效。通过对于压降、强化传热以及两者结合影响等考虑多种因素的换热网络优化改造方法研究和实例的验证,本文所提出的考虑多因素的换热网络优化改造方法对于换热网络优化改造方法的研究和发展具有积极的促进作用和重要的实用价值。更多还原

【Abstract】 Heat exchanger networks synthesis and retrofit have been the most important subjects during process integration field. The impact of network retrofit on improving energy saving has obvious effect. During the last over50years, various kinds of methods have been developed for heat exchanger network synthesis andretrofit. There has been made rapid process in this subject. The research results have been extensively to actual process industry for obtaining large energy-saving benefit. After1990s, due to rising energy prices, these subjects have attracted much more attention from researchers. The main focus of heat exchanger network retrofit is to develop a more effective and practical retrofit method, which can remove impractical assumptions and avoid unfavourable computational complexity. Research advances in retrofit approaches have an importent influence on improving energy recovery of the whole process industry’.This paper mainly contributes to propose a novel simultaneous approach for heat exchanger network retrofit considering multiple factors-topology modification, heat transfer enhancement and pressure drop limitation. Our main work includes four aspects as follows:1、Mathematical model of heat exchanger network retrofit. We proposed an improved stage-wise superstructure for heat exchanger network retrofit problems, which consists of exsiting exchangers, new heat exchangers, additional area and exchangers reassignments. Based on the improved superstructure, a simultaneous optimization mathematical model without the assumption of isothermal mixing is formulated to solve retrofit problems, which is a mixed integer non-linear programming model.2、Heat exchanger network retrofit with considering pressure drop. Based on the stage-wise superstructure model, the stream pressure drop calculation formulations are incorporated into the retrofit mathematical model for considering pumping device and pumping power costs during the total annual cost. In this study, a two-level optimization strategy is used for solving the above-mentioned complex model. In the outer level, the genetic algorithm has been used for generating new network structures and finding the optimal one. In the inner level, the PSO/GA hybrid algorithm has been used for optimizing operating parameters and sending the best cost of the achieved to the upper level for determination of fitness of existing network structure. The research results prove that the retrofit approach considering pressure drop enables the designer to study tradeoff among pumping cost, additional area cost and operating cost of the network, and is therefore to be reliable and applicable in engineering design.3、Heat exchanger network retrofit with considering heat-transfer enhancement. Heat transfer enhancements are very attractive options for heat exchanger network retrofit. To consider the influence of heat transfer enhancement on the retrofit option, combined with practical heat transfer enhancement techniques, an extended retrofit model is proposed to obtain a trade-off among enhancement cost, topology adjustment cost and operating cost. The case study indicates that the extended model can reasonably find the enhancement position in the network. During the optimal network topology, reasonable heat transfer enhancement may decrease the additional area demanding, and therefore a more optimal solution can be obtained with lower investment costs and investment recovery period.4、Heat exchanger network retrofit with considering heat-transfer enhancement and pressure drop limitation. Based on the researche results of heat exchanger network retrofit approaches with considering heat-transfer enhancement and pressure drop respectively, a more practical retrofit model considering the relationship between the heat transfer enhancement and increasing pressure drop is proposed to avoid the unreasonable pressure drop. A project case is studied to analysis the pressure drop control method through designing reasonable geometry structure of heat exchangers. The research results show that several exchanger structure modification methods are effective in tackling the problem of increased pressure drop. Among those exchanger structure modification methodologies, changing the shell arrangement and using helical baffle are effective in mitigation increases in the shell sidel pressure drop. Changing the shell arrangement and reducing the number of tube passes can be used to reduce the tube side pressure drop. Through the research results of heat exchanger network retrofit with considering multiple factors-network topology modifications, heat transfer enhancement and pressure drop, the proposed approach and the conclusions have important value of not only in theory but also practicality on the research field of heat exchanger network retrofit.更多还原