Performance evaluation of convective heat transfer and laminar flow of non-Newtonian MWCNTs in a circular tube. (1st October 2021)

• Record Type: Journal Article
• Authors: Ajeeb, Wagd; Oliveira, Monica S.A.; Martins, Nelson; Murshed, S.M. Sohel
• Is Part Of: Thermal science and engineering progress. Volume 25(2021)
• Publication Date: 2021-10-01
• Subjects: Non-Newtonian fluid -- Nanofluids -- CFD -- Heat transfer characteristics -- Laminar flow; Heat engineering -- Periodicals; Heat engineering; Thermodynamics; Periodicals; 621.402
• DOI: 10.1016/j.tsep.2021.101029
• Languages: English
• ISSNs: 2451-9049

Abstract

Highlights: Heat transfer of non-Newtonian nanofluids in tube is studied. Rheology and temperature-dependent properties of the nanofluids are modelled. Heat transfer enhancement and Energy efficiency for laminar flows are investigated. Abstract: Nanofluids are often designed to improve their heat transfer characteristics. However, there are some challenges regarding the increase in their viscosity and the change of the rheology. Therefore, this study investigates the laminar flow of non-Newtonian MWCNTs nanofluids in a circular tube under a constant wall heat flux condition. The rheological behavior and thermal conductivity of the nanofluids are modelled using suitable correlations derived from an experimental database. A numerical approach by finite volume method (FVM) is used for modelling the heat transfer and the laminar flow conditions in this study. The thermal behavior and the non-Newtonian characteristics of the MWCNTs nanofluids are evaluated concerning heat transfer, pressure drop and the overall energy efficiency of the system. The obtained results show that the heat transfer performance is enhanced by adding nanoparticles to the base fluid, reporting an average heat transfer enhancement of about 8.7% and 12.4% for 0.25% and 0.5% concentrations of MWCNTs, respectively. Also, it was found an average increase in pressure drop of about 9.1% and 15.3% for 0.25% and 0.5% concentrations of MWCNTs, respectively. Moreover, the overall energy efficiency of the system is enhanced by using MWCNTs nanofluids for high Reynolds number (1000 ≤ Re ≤ 2000), reaching a maximum enhancement at Re = 1000. The methodology here developed and validated, establishes an important breakthrough concerning modelling and prediction of MWCNTs nanofluids towards its tailoring for subsequent heat transfer studies and applications.