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Heat exchanger network synthesis with detailed exchanger designs—2. Hybrid optimization strategy for synthesis of heat exchanger networks
AIChE Journal ( IF 3.5 ) Pub Date : 2020-09-13 , DOI: 10.1002/aic.17057
Saif R. Kazi 1 , Michael Short 2 , Adeniyi J. Isafiade 3 , Lorenz T. Biegler 1
Affiliation  

We propose a new strategy to synthesize heat exchanger networks with detailed designs of individual heat exchangers. The proposed strategy uses a multistep approach by first obtaining a heat exchanger network topology through solving a modified version of the mixed integer nonlinear programming (MINLP) stage‐wise superstructure of Yee and Grossmann, which includes a smoothed LMTD approximation and pressure drops. In a second nonlinear programming (NLP) suboptimization step, we allow for nonisothermal mixing to solve problems with or without exchanger bypasses. The selected heat exchangers along with the mass and energy balances obtained are then used to design the network with detailed exchanger designs through solving a sequence of NLPs for individual heat exchanger designs. The NLPs are based on the detailed discretized optimization models of Kazi et al., which solve quickly and reliably to obtain heat exchangers based on rigorous, first‐principles derived coupled differential equations. These models solve a differential algebraic equation system and do not rely on usual assumptions associated with other heuristic‐based exchanger design methods, such as log mean temperature difference and FT correction factors. These detailed exchanger designs are then used to update the network optimization model through sets of correction factors on heat exchanger area, number of shells, heat transfer coefficients, and pressure drops of each exchanger design, in a method based on that of Short et al. The method solves reliably, guaranteeing feasible exchangers for every potential network generated by the shortcut models, through validation with rigorous heat exchanger models at every iteration. In addition, the method does not increase the nonlinearity of the MINLP model, nor does it require any manual intervention or initialization from the user. Three examples are solved and the results are compared to those obtained in the literature.

中文翻译:

带有详细交换器设计的热交换器网络综合— 2。换热网络综合的混合优化策略

我们提出了一种新的策略,通过各个热交换器的详细设计来综合热交换器网络。拟议的策略使用多步方法,首先通过求解Yee和Grossmann的混合整数非线性规划(MINLP)阶段上层结构的修改版本来获得热交换器网络拓扑,其中包括平滑的LMTD近似值和压降。在第二个非线性规划(NLP)次优化步骤中,我们允许进行非等温混合,以解决有无热交换器旁路的问题。然后,通过解决单个换热器设计的一系列NLP,将选定的换热器与获得的质量和能量平衡一起用于设计具有详细换热器设计的网络。NLP基于Kazi等人的详细离散优化模型,该模型可快速可靠地求解,以基于严格的,第一性原理导出的耦合微分方程获得热交换器。这些模型解决了微分代数方程组系统,并且不依赖于与其他基于启发式的交换器设计方法(例如对数平均温度差和F T校正因子。然后,根据Short等人的方法,将这些详细的换热器设计用于通过对每个换热器设计的换热器面积,壳体数量,传热系数和压降校正因子集来更新网络优化模型。通过在每次迭代中使用严格的换热器模型进行验证,该方法可靠地解决了问题,并保证了由快捷模型产生的每个潜在网络的可行换热器。此外,该方法不会增加MINLP模型的非线性,也不需要用户进行任何手动干预或初始化。解决了三个示例,并将结果与​​文献中的结果进行了比较。
更新日期:2020-09-13
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