The HYSYS model for heat exchanger networks shows the issue of a low ft correction factor
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I have a question for the experts here. I am working on creating a model of an atmospheric pressure tower with a heat exchange network, as shown in the diagram below: there is one preheating train and one atmospheric pressure tower. When I make slight changes to the specifications of the atmospheric pressure tower, the model converges, but the heat exchange network does not converge; it shows that the FT correction factor is low. What can I do to resolve this issue? Since I want to optimize the operation of the atmospheric pressure tower, I need to adjust the variables in its specifications within a certain range. If changing these variables causes problems with the heat exchange network, optimization becomes impossible. I hope the experts can help me
This indicates that the temperature difference at the hot end is a bit small, and temperature crossover may occur
Increase the temperature after cooling of the heat flow, or decrease the temperature after heating of the cold flow
This is likely just a warning indicating an insufficient number of shell sides in the heat exchanger, as shown in the following English text. The number of shell passes is set to 1 by default; changing it to 2 or a higher value will do. This is generally a warning and does not cause convergence issues. Moreover, your model is converging; what appears is just a warning. Problem Statement: HYSYS warns me that my Heat Exchanger has a “Ft Correction Too Low” – what does it mean? Solution: The Ft factor (LMTD Correction Factor) is related to the shell & tube configuration (shell/tube passes). From a practical economic perspective, it is rare that a configuration with an Ft value of less than around 0.8 would be chosen. HYSYS issues a warning when the Ft factor for a given heat exchanger is below 0.8. The heat exchanger will still be analyzed and its performance rated (results will be available); it’s merely a warning that this configuration may not be the optimal one. This warning can generally be resolved by adding more shells to the design.