Exploiting Tube Inserts to Intensify Heat Transfer for the Retrofit of Heat Exchanger Networks Considering Fouling Mitigation

Recent studies on heat-transfer intensification have shown that the use of tube inserts is an effective way of enhancing heat transfer while mitigating fouling deposition in shell-and-tube exchangers. Thus, this intensification technique has been used for the retrofit of heat exchanger networks (HENs) in the process industry. Unlike most existing research assuming constant fouling resistance in HEN retrofit procedures, this article presents a novel optimization method to address fouling effects for HEN retrofit problems. In the new approach, tube inserts (tube-side intensification) can be implemented to increase the heat-transfer coefficients of intensified exchangers, and an actual detailed tube-side fouling model is applied to calculate the tube-side fouling resistance in each heat exchanger. However, this usually leads to very large complex computational problems because of the combination of the HEN retrofit model and the exchanger fouling model. To reduce the resulting nonlinear computational difficulties, the optimization procedures proposed by Pan et al. (Comput. Chem. Eng. 2012, 42, 263-276; Appl. Therm. Eng., published online Apr 21, 2012,) were developed and updated based on retrofit scenarios. In a case study, the retrofit of a practical industrial process was studied to demonstrate the validity and soundness of the proposed approach, showing that the benefit derived from implementing tube inserts is not only increased heat recovery but also prolonged exchanger operating times through the mitigation of fouling deposition.