Design construtal para alto desempenho em arranjos de tubos e micromisturadores via simulação numérica

Abstract

The combination of the Response Surface Method (RSM) and Constructional Design Method (CDM) was applied in the investigation of two problems: configurations of tube arrangements for heat transfer in pseudoplastic fluids and geometric optimization of micromixers. Concerning the first problem, tube arrangement systems were modeled such that three cases, with one, two, and four degrees of freedom were evaluated in terms of dimensionless heat transfer density. In the second problem, micromixers with cylindrical obstacles, whose vertical and horizontal positioning, were evaluated, totaling two degrees of freedom. Subsequently, the number of obstacles is also investigated, so one more degree of freedom was considered. The modeling of the described systems was elaborated and solved using numerical simulations via Computational Fluid Dynamics (CFD), through the finite volume method (FVM). Viscosity modeling for the pseudoplastic fluids was performed using the Power-Law model, while mixing modeling, in the second problem, the Species model was used. For both problems, continuity, and Navier-Stokes equations were solved. The application of the RSM methodology was done in open-source code, where the necessary experiments were designed using the Central Composite Design method, and, later, used to elaborate the polynomial model needed to create the response surfaces. Concerning the first study, it was noted that the heat transfer density is directly dependent on the distance between cylinders and that the greater the degree of pseudoplasticity of the fluid, the greater the performance in heat transfer. A significant difference in configuration was noticed when pseudoplastic and Newtonian fluids were used. For the former, the configuration tends to be more compact, so that smaller spacings and larger cylinders can be developed, contrary to the tendency presented by Newtonian fluids. Concerning the second study, it was observed that the greater the number of obstacles, the greater the mixture obtained. However, the energy required is also greater. By introducing the Mixing Energy Cost (MEC), designs with three obstacles were more efficient, while the one with seven (maximum evaluated value) had the worst index. However, the local pressure gradient is smaller for larger amounts of obstacles. By modifying degrees of freedom, it was possible to ensure that the system evolved so that the objective of the systems (heat and mass transfer) could be increased, thus ensuring higher performance, even for simple configurations.