Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Counterflow heat exchanger simulation with the Lattice-Boltzmann Method
Submission Author:
Vinicius Akyo Matsuda , MG
Co-Authors:
Vinicius Akyo Matsuda, Ivan Talão Martins, Edilson Guimarães de Souza, Luben Cabezas Gómez
Presenter: Vinicius Akyo Matsuda
doi://10.26678/ABCM.COBEM2023.COB2023-1486
Abstract
In this work the Lattice-Boltzmann Method (LBM) is used to simulate and study a simple counterflow heat exchanger. For this purpose, the D2Q9 dimensional LBM with single and multiple relaxation times, considering the BGK (Bhatnagar-Gross-Krook) and the MRT (Multiple-relaxation-time) collision operator, respectively, were used. Two distribution functions were used to correctly model the problem, one for the Navier-Stokes equation, and the other for the energy conservation equation. Furthermore, an enthalpic based LBM was used to model the conjugate heat transfer between the fluids and the heat exchangers walls. More precisely, the simulation results obtained with the LBM were compared against simulation results derived from traditional simulation techniques, such as the effectiveness-NTU method. Performing this comparison we expect to illustrate the capabilities of the LBM and demonstrate the impacts of the adopted hypotheses in common heat exchanger design simulations techniques. However, firstly a theoretical benchmark test problem was simulated with the LBM, making a comparison with available analytic solutions, in order to check and guarantee the correct behavior of the LBM numerical solutions. The present LBM model was shown to correctly predict the theoretical solution, allowing for the validation of both the LBM model and the numerical code employed in the simulations. The LBM results obtained for the simulated counterflow heat exchanger showed that both inlet regions for both fluids present a significant impact on the real effectiveness of the heat exchanger. Within these regions, the errors between the LBM and effectiveness-NTU methods were the highest, showing the importance in simulating the non-developed thermal and flow regions. Although these higher errors mainly occurred in a small region of the heat exchanger, they were shown to build up to a few temperature degrees, indicating that they can impact on the correct design of the simulated devices. The noted differences can be more important for applications with lower mass flow rates.
Keywords
Lattice Boltzmann method, Heat exchanger, BGK, conjugate heat transfer, Navier-Stokes, Effective properties, MRT, dimensional LBM
