Seminário de Avaliação - Série A: Advanced modeling strategies for crystallization fouling incorporating CaCO₃ polymorphism

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

Banca Examinadora:
Renato Simões Silva - 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:
José Karam Filho - Laboratório Nacional de Computação Científica - LNCC

Resumo:

Crystallization fouling is a prevalent phenomenon in various industrial systems. This buildup reduces thermal efficiency by inc reasing thermal resistance in heat exchangers. Additionally, it results in higher maintenance and energy consumption costs. The net fouling 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 governed by hydrodynamic forces and the break-off mechanisms acting on the deposited layer. Regardless of the fouling-type, it typically involves five key stages: initiation, transport, attachment, removal, and aging. The deposited material undergoes aging, leading to crystal size evolution and changes in its mechanical (e.g., material strength and Young’s modulus) and thermal (e.g., thermal conductivity and density) properties. Consequently, the break-off of crystalline deposits may take place when thermal stresses exceed the material stren gth. Building on the break-off model for CaCO3 reported by Babuška, Silva and Actor (2018), the present work aims to propose a new crystallization fouling model that enhances the aging treatment considering the CaCO3 polymorphs. This requires applying the population balance equation (PBE) to describe the crystal size evolution and the relative concentrations of the CaCO3 polymorphs over time, ensuring a consistent characterization of the aging process. The PBE is a hyperbolic integro-differential partial differential equation, which may lead to numerical complexities due to instabilities caused by steep solution gradients.To overcome these computational challenges, various Petrov Galerkin Finite Element Methods (PG-FEM) are considered. To approximate the scalar temperature fields of the fouling-wall structure and the water, the heat transfer models must be formulated using parabolic and hyperbolic partial differential equations. In addition, to consistently reproduce fouling evolution, we address the problem as a moving boundary problem, capturing the displacement of the fouling layer surface. Thus, a hybrid interface capturing strategy is proposed to approximate this movement. The proposed model enables an improved characterization of the crystallization fouling process.