Fouling is one of the main causes of industrial problems regarding operation and control of shell and tube heat exchangers. Although fouling is a time dependent phenomenon, most papers in the literature focus on fouling mitigation in steady-state heat recovery. In this work, a lumped parameter model to describe time-varying conditions and their influence in controller tuning is presented. For each modeling cell, there are four input variables (inlet temperatures and flow rates for shell and tube sides), which generate two output signals (outlet temperatures for shell and tubes). The influence of fouling in process control is evaluated by considering intermediate values of thermal resistance of fouling (R_f), simulating its variation with time. The model was implemented in MATLAB/Simulink, and simulations have been carried out for different periods of operation. A step change was applied in the shell flow rate to evaluate the response in the tube outlet temperature. Results show that periodic fitting in proportional integral derivative (PID) parameters are needed to keep the tube outlet stream at the desired temperature. Moreover, two optimization strategies are presented for tuning controller gains constrained by some step response performance indicators. Three case studies have been taken as benchmarks, and results show that this strategy is promising.

中文翻译：

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克服比例积分微分受控换热器结垢影响的调整策略

结垢是关于管壳式热交换器的操作和控制的工业问题的主要原因之一。尽管结垢是一种与时间有关的现象，但文献中的大多数论文都专注于稳态热回收中的结垢缓解。在这项工作中，提出了用于描述时变条件及其在控制器调整中的影响的集总参数模型。对于每个建模单元，有四个输入变量（壳体和管子侧面的入口温度和流速），生成两个输出信号（壳体和管子的出口温度）。通过考虑结垢热阻的中间值（R _f），模拟其随时间的变化。该模型是在MATLAB / Simulink中实现的，并且已针对不同的运行周期进行了仿真。壳流速采用阶跃变化来评估管出口温度的响应。结果表明，需要定期拟合比例积分微分（PID）参数，以将管出口流保持在所需温度。此外，提出了两种优化策略来调整受某些阶跃响应性能指标约束的控制器增益。以三个案例研究为基准，结果表明该策略是有前途的。