Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Single-phase and multi-phase simulation of laminar flows of isopropanol/Al2O3 in a tube of circular cross section
Submission Author:
Pedro Coelho , Lisboa , Portugal
Co-Authors:
Nikolaos Trokas, Pedro Coelho
Presenter: Pedro Coelho
doi://10.26678/ABCM.ENCIT2022.CIT22-0072
Abstract
Nanofluids have emerged in the past few decades as a very promising and modern technique for heat transfer enhancement. The main reason is the increase of the thermal conductivity compared to the base fluid. A lot of experiments and computational work has been done to better understand the behaviour of nanofluids and verify their theory. Numerically, single-phase and multi-phase approaches can be used to study nanofluids. The multi-phase approach seems to be most accurate method for numerical simulations, although requiring greater computational cost. Three different multi-phase models have been used for nanofluid flows modelling, namely Eulerian-Mixture, Eulerian-Eulerian and Eulerian-Lagrangian. In this study, these three models are analyzed for an Al2O3 / isopropanol flow in a tube of circular cross-section. Experimental data are used to assess the accuracy of the results. In addition, results from a previous work using a single-phase model are included in the analysis to evaluate the two approaches. The heat transfer coefficient was computed for various inlet temperatures (15℃ and 25℃), Reynolds numbers (laminar flow) and nanoparticle concentrations (0.387 to 4.71% on a mass basis). The main purpose of the work is focused on the accuracy of the three multi-phase models It was found that two-phase models yield better results than the single-phase model for all studied cases. The three models closely match the experimental values for low particle mass fraction, while some discrepancies are observed for the Eulerian-Eulerian model in the case of high particle mass fraction. So, in general, the Eulerian-Mixture and the Eulerian-Lagrangian models were found to be more precise for the heat transfer simulations performed in the present work. As far as the computational cost is concerned, the Eulerian-mixture model requires less computational time while yielding very reliable results.
Keywords
Nanofluids, Nusselt number, Heat transfer enhancement, Multi-phase flows
