Heat Exchanger Design Optimization Considering Threshold Fouling Modelling

Abstract

Abstract In heat exchangers, fouling is the undesired accumulation of deposits over the equipment thermal surface. This phenomenon causes a gradual reduction of the overall heat transfer coefficient. The traditional approach to handle the fouling problem during the design consists in the introduction of fouling factors in the evaluation of the (dirty) overall heat transfer coefficient. However, this approach ignores the fact that the fouling rate is dependent on the flow velocity and temperature. Aiming to fill this gap, this paper investigates the optimization of the design of heat exchangers including fouling modelling. Among the many fouling manifestations, this investigation focuses on chemical reaction fouling in crude oil streams associated to the presence of asphaltenes, modelled by a threshold model (Ebert Panchal model and its variants). According to this model, there are conditions of surface (or film) temperature and flow velocity where there is no fouling. The developed formulation of the design problem employs a mixed integer linear programing approach, where the geometry-related design variables are defined based on standard values. The results are compared with a traditional approach with fixed fouling factor, which indicates a potential reduction of capital costs.