CFD modelling of heat transfer and pressure drops for nanofluids through vertical tubes in laminar flow by Lagrangian and Eulerian approaches

Abstract

Nanofluids consist of liquid and solid (nanoparticles), therefore, they can be classified as two-component flow, which brings up different approaches for simulation purposes. In this study, heat transfer and hydro-dynamic features of nanoparticles in a laminar nanofluid flow in a vertical tube are investigated numerically via Lagrangian and Eulerian approaches.Discrete Phase Model (DPM) in Lagrangian approach simulates the motion of particles through base flow with force balance equation, therefore, no needs empirical correlations at least for the thermo-physical properties (which they are not universal and change for different fluids and/or nanoparticles). Although, general empirical or analytical correlations are needed for some interactions between solid and liquid such as Thermophoresis, Brownian and clustering effects, but they are not that extensive and can be employed in most of the cases.Mixture model in Eulerian approach provides more reliable results, but it highly depends on the accuracy of the correlations for the thermo-physical properties of the nanofluid. In present study, three common types of nanofluids consist of Alumina, Zirconia and Silica nanoparticles (up to 2.76% of volume fraction) are studied and the results are compared with experimental works. Numerical simulations indicate that the findings are in good agreement with the measured heat transfer coefficient for DPM. Consequently, DPM can be highly recommended for simulation study due to the strength and simplicity. It has been also observed that the effects of nanoparticles in each computational cell need to be distributed to the other neighbourhood cells. Pressure losses results predicted by DPM were found reliable for volume fraction less than 3%, no matter the types of nanoparticles or diameter. DPM velocity profiles show that the slip velocity between nanoparticles and base flow is not negligible.

Entrance length effects on Graetz number scaling in laminar duct flows with periodic obstructions: Transport number correlations for spacer-filled membrane channel flows

“…In channel flows with nanoparticles, such a redistribution can also result from a non-homogenous distribution of particles as recently shown by Mahdavi et al [37]. Additionally, a partial-slip boundary condition, caused by the addition of nano-particles, as discussed in Turkyilmazoglu [38] results in a redistributed velocity profile and thus contributes to an increase in Nusselt number.…”

Laminar Forced Convection and Entropy Generation of ZnO-Ethylene Glycol Nanofluid Flow through Square Microchannel with using Two-Phase Eulerian-Eulerian Model

“…In addition, the obtained results for convective heat transfer enhancement with two-phase modeling are higher compared to that of single-phase and convective heat transfer enhancement increases with decrease in nanoparticle diameter. Mahdavi et al (2015) separately applied the discrete phase model in the Lagrangian approach and mixture model in the Eulerian approach to water based Al2O3, SiO2 and ZrO2 nanofluid flows through vertical tube under laminar flow conditions. As a result, they recommended the discrete phase model due to its strength and simplicity.…”

Evaluation of single-phase, discrete, mixture and combined model of discrete and mixture phases in predicting nanofluid heat transfer characteristics for laminar and turbulent flow regimes

“…Numerical investigation of forced convective heat transfer for water Al 2 O 3 nanofluid inside a circular tube under constant wall heat flux has been investigated by several researchers [6,32,36,43]. Furthermore, some researchers devised new models to simulate nanofluids based on their opinions on which phenomenon contributed more to the nanofluid's behavior [33,36,37,56,74,75]. Several models have been used to simulate nanofluids.…”