Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Constructal Design and Response Surface modeling of tube arrangement heat exchanger with two degrees of freedom for pseudoplastic and viscoplastic fluids
Submission Author:
Eduardo Henrique Taube Cunegatto , RS
Co-Authors:
Eduardo Henrique Taube Cunegatto, Marcelo Gotardo, Flavia Zinani
Presenter: Eduardo Henrique Taube Cunegatto
doi://10.26678/ABCM.ENCIT2022.CIT22-0082
Abstract
The Constructal Design Method (CDM) originates from the Constructal Law, which states that every system, to remain alive, evolves in the direction of facilitating the flows that constitute the purpose of this system. CDM is used in engineering to design optimal performance configurations from the point of view of greater access to their flows. Tube arrangements are used as heat exchangers and the study of their configurations for different operating conditions is a research topic that still has many questions unanswered. In this work, CDM was used to analyze tube arrangements for heat transfer with non-Newtonian fluids – pseudoplastic and viscoplastic – seeking the configuration that returns the maximum heat transfer density. Systems consisting of a row of tubes added by secondary tubes were analyzed, according to the hierarchy principle present in the Constructal Theory. In these systems, there are two degrees of freedom – the distance between the tubes and the tubes’ diameter ratio. The systems were modeled by the Computational Fluid Dynamics (CFD) solutions, using the Power-Law and Bingham equations to predict the viscosity of pseudoplastic and viscoplastic fluids, respectively, in the ANSYS Fluent software. The Rstudio software was used to design the experiments by the Central Composite Design method, and to adjust the Response Surfaces by a second-order model. The models obtained were able to predict the behavior of the systems and the optimal configurations, with a small number of runs, thanks to the Design of the Experiments techniques. The results showed that the pseudoplastic fluids provide the highest heat transfer densities, due to the shear-thinning effect. Considering the three fluid models, the results showed that the heat transfer density is highly dependent on the two parameters (degrees of freedom) and that the interaction between the parameters is significant. The optimal configurations obtained differ considerably for each fluid – larger tubes and smaller spaces are beneficial to pseudoplastic fluids, while for viscoplastic, the opposite occurs. The blend of statistical, optimization, and numerical tools to the CDM is outstanding, as it allows system design for complex fluids, optimizes the number of experiments and contributes to the operation of thermal systems to reach their best performance point.
Keywords
Constructal Design, Heat Exchanger Design, Non Newtonian Fluids, CFD, Optimization, Rheology
