Empirical versus Systematic Methods for HEN Resilience

The conventional procedure for introducing resilience in a HEN (or general process plant) is to use empirical overdesign. That is, a nominal or conservative basis is selected for designing and optimizing the HEN. Empirical safety factors based on past experience are applied to the equipment sizes and extra units are also often introduced. However, although this empirical procedure will in general add resilience and 

Not much insight is gained on how much (if any) resilience is added for a given degree of overdesign. 

The most conservative or worst case basis for design may not be the one the designer would intuitively expect. 

Conditions that give rise to infeasible operation may not be detected since interactions among different exchangers are not explicitly taken into account. 

The resulting overdesigned network may not operate efficiently and may not be optimal from an economic viewpoint. 

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