建構熱交換器網路是回收廢熱常見的處理方式，在能源缺乏的時代中顯得更為重要，然而熱交換器在實際操作下會在熱傳表面上結垢，降低熱交換器的熱傳效率並增加能源成本。在過去的研究中，Cheng and Chang (2016)曾提出具備件的熱交換器網路清洗排程來改善結垢的問題，雖然可以有效的降低公用流體成本，但是在正常操作時，熱交換器網路仍然會受結垢的影響而花費額外的能源成本，且關於備件的設備成本仍嫌過高。針對結垢在正常操作時的解決方案，Sun et al. (2008)曾建議在熱交換器增設裕度並以旁路輔助來調節溫度，但未提及關於清洗的相應改善措施。因此本研究探討如何針對既有的熱交換器網路，利用備件、裕度、旁路與輔助單元的配置規劃出最適當的清洗排程。具體而言，我們修改已存在的MINLP且利用網路結構矩陣分析出備件的配置策略，並利用敏感度分析決定增設裕度的優先順序，且藉增設旁路來增加可控性以及輔助單元讓每個出口溫度都能到達目標溫度。在相應的最適解中，決定清洗排程、備件的熱傳面積與使用排程、裕度面積如何設計等。最後，在本研究中的兩個案例探討中驗證所提方法之可行性與有效性。

Fouling develops in almost any heat exchanger during normal operation. This inevitable deterioration in heat-transfer efficiency of one or more units in the heat-exchanger network (HEN) of a chemical plant obviously raises the hot and cold utility consumption levels. To address the practical issues caused by fouling, it is necessary to modify the traditional HEN design so as to accommodate a proper cleaning schedule.
In this study, the existing model has been modified to generate optimal cleaning schedules that are supported by spares and the reserved margins in exchangers. The former options are basically represented with binary variables in the modified model, and each is used to reflect whether a removed exchanger should be replaced with a spare. For introducing margin and bypass into the model, the heat-transfer area of each chosen unit and bypass flowrates are treated as variables in the modified model formulation. In order to allocate the spare-supported units, the connections of heat exchangers in HEN are analyzed in this study by the connections sequence matrix. On the other hand, the sensitivity analysis is adopted to identify the critical heat exchangers which require margins.
By solving the modified model, one should be able to obtain the optimal cleaning schedule, the time-dependent flowrates of bypasses and utilities, the heat transfer areas of all margin-embedded heat exchangers, the heat transfer areas of spares, and the optimal spare replacement schedule. Finally, the optimization results of a case study will be presented to demonstrate the feasibility and effectiveness of the proposed approach.

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