Exame de Qualificação: New Strategies for Modeling Crystallization Fouling

Orientadores:
Renato Simões Silva - Laboratório Nacional de Computação Científica - LNCC
Regina Célia Cerqueira de Almeida - Laboratório Nacional de Computação Científica - LNCC

Banca Examinadora:
José Karam Filho - Laboratório Nacional de Computação Científica - LNCC (presidente)
Diego Tavares Volpatto - Laboratório Nacional de Computação Científica - LNCC
Alvaro Luiz Gayoso de Azeredo Coutinho - Universidade Federal do Rio de Janeiro - COPPE/UFRJ

Suplentes:
Fabio Pereira dos Santos - Laboratório Nacional de Computação Científica - LNCC

Resumo:

Crystallization fouling is a prevalent phenomenon in various industrial systems. This buildup reduces thermal efficiency by increasing thermal resistance in heat exchangers. Additionally, it resultsin higher maintenance and energy consumption costs [1]. The net foul ing rate on heat exchanger walls depends on the balance between deposition and removal rates. Deposition occurs when crystals, transported by diffusion from regions of high to low concentration, adhere to the heat transfer surface at a specific attachment reaction rate. In contrast, the removal process is driven by hydrodynamic forces and shear stresses acting on the deposited layer. Regardless of the fouling­type, it typically involvesfive key stages: (a) initiation, (b) transport, (c) attachment, (d) removal, and (e) aging [2]. During the finalstage, the deposited material undergoes aging, which results in crystal size evolution. Changes in crystal size alter key mechanical properties (e.g., material strength, Young’s modulus, and hardness) [3] and thermophysical properties(e.g., thermal conductivity and density). As a consequence, mechanical failure and subsequent break­off of crystalline deposits may due to changes in the material’s strength [4]. This work extends a previous stu dy reported by Babuška et al [4]. Our aim consists in proposing a new mathematical fouling model that offers an improved treatment of aging and break­off mechanisms. This requires introducing an energy model to characterize the heat transfer process, analyzing the temporal evolution of the fouling layer, and applying the population balance equation to describe crystal size evolution. [5]. These phenomena can be modeled using partial differential equations, which may lead to numerical complexities due to instabilities caused by steep solution gradients. To overcome these computational challenges, various Stabilized Finite Element Methods are considered [6]. The proposed model enables an improved description of property changes and provides a more precise characterization of both the aging and rupture of the fouled material.