Suppose we have a HEN with several multi-pass heat exchangers. However, due to some technical constraints all these exchangers are modelled simply using single pass equations.
What will the impact if such a simplistic model is used in optimization problems, such as network optimization for retrofitting or cleaning scheduling?
For instance, it is clear that we may not end up with global optimal solutions but still what will the qualitative impact of such approximations?
Dear friend Parag Patil
The impact of using a simple model for multi-pass heat exchangers in optimization problems can be significant. The use of single-pass equations can lead to suboptimal solutions and may not be able to capture the true behavior of the system. However, the qualitative impact of such approximations will depend on the specific problem being considered and the degree of simplification used.
For instance, according to a research paper on ResearchGate (Heat Exchanger Design and Optimization........), using data modeling, the optimization of a heat exchanger can be transformed into a constrained optimization problem and then solved by modern optimization algorithms. In this way, it is possible to obtain optimal solutions for complex heat exchanger designs.
In another research paper on SpringerLink (Topology design of two-fluid heat........), simplified models have been studied for solving turbulent heat transfer problems, natural convection problems, and heat exchanger design problems. The study proposes a simple representation model for topology optimization of two-fluid heat exchange. It introduces two types of fictitious force terms, one in each flow field, for representing a wall between the two types of fluid.
I hope this helps! Let me know if you have any other questions.
Source:
(1) (PDF) Heat Exchanger Design and Optimization - ResearchGate. https://www.researchgate.net/publication/356630032_Heat_Exchanger_Design_and_Optimization.
(2) Topology design of two-fluid heat exchange | SpringerLink. https://link.springer.com/article/10.1007/s00158-020-02736-8.
(3) Topology optimization of heat exchangers: A review. https://www.sciencedirect.com/science/article/pii/S0360544222009562.
(4) Design Optimization of Heat Exchangers with Advanced Optimization .... https://link.springer.com/article/10.1007/s11831-019-09318-y.
Quick note: optimization often pushes systems towards extreme configurations. Make sure your model will still work well in relevant extreme configurations, or else add appropriate for constraints to prevent extreme configurations.
It seems that you are looking at a network of heat exchangers all of which have been modelled very crudely, so how do the errors in one unit affect the next etc. There is no simple answer to this, in many cases "The Law of Compensating Errors" applies as the second unit makes up for the deficiency of the first etc. But this is not a natural law so cannot be relied on. Generally, if the final answer is reasonably close to experience the simple model is okay, otherwise more detailed analysis is needed.
To formulate of this model you need to consider the amount of information included in it:
1. Article Uncovering the Hidden Information: A Novel Approach to Model...
2. Preprint A new look at the process of modelling physical phenomena: I...
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