Laminar rarefied flow analysis in a microchannel with H2O-Cu nanofluid: A thermal lattice Boltzmann study

Abstract

This research paper presents an investigation into the behavior of rarefied flow and heat transfer in a rectangular microchannel utilizing a Cu-water nanofluid. The study employs the thermal lattice Boltzmann method (LBM) with a lattice featuring a double distribution function and a BGK collision model. The simulations are performed using Python software, incorporating slip velocity and temperature jump effects. The primary objective is to analyze the influence of various thermophysical parameters of the coolant fluid on the microchannel, specifically focusing on the characteristics of the Cu-water nanofluid. The study considers laminar flow conditions with nanofluid volume fractions of 2%, 4% and 6%. The findings reveal that both rarefaction effect and Reynolds numbers, as well as the nanoparticle volume fraction, significantly impact the system. Moreover, the investigation evaluates key parameters such as the Nusselt number, skin friction coefficient, temperature jump slip velocity and velocity and temperature profiles. Notably, the nanoparticle volume fraction exhibits minimal influence on the velocity distribution or temperature field, whereas the Nusselt number increases with higher nanoparticle volume fractions. Additionally, the rarefaction effect leads to a reduction in velocity and temperature. At a nanoparticle volume fraction of 2%, increasing the Reynolds number results in elevated velocities and lower temperatures. The skin friction coefficient displays a decreasing trend along the microchannel with increasing Reynolds numbers. Furthermore, an increase in Knudsen numbers corresponds to a decrease in the skin friction coefficient. Finally, an increase in the nanoparticle volume fraction is associated with a decrease in the skin friction coefficient.