Thermal Behavior of Carboxymethyl Cellulose Containing Alumina Nanoparticles at the Entrance Region of an Annulus

This paper investigates the thermal behavior of non-Newtonian nanofluids, specifically carboxymethyl cellulose (CMC) ۰.۵% and Al₂O₃ nanoparticles, in the fully developed region of a horizontal annulus. A three-dimensional axisymmetric, steady-state numerical solution is performed using the mixture multiphase model to compare with the results obtained from the single-phase model. The present study examines the effects of nanoparticle volume fraction ranging from ۰.۵% to ۱.۵% and particle diameters of ۲۵ nm and ۵۰ nm for various Reynolds numbers (Re) within the laminar flow regime. The results indicate that while the temperature profile distribution is slightly affected by changes in alumina concentration, significant variations are observed in the entrance region. Specifically, as Re is enhanced, the Nusselt number (Nu) is increased. For an outer wall heat flux of ۱۰۰۰ W/m² and a ۱% concentration, Nu at the x/L = ۰.۲۵ section augments from ۶.۹۲ to approximately ۱۳.۱۴ as Re is enhanced from ۵ to ۵۰۰. Additionally, for the same conditions, Nu is about ۰.۷۸% higher for Al₂O₃ nanoparticles with a diameter of ۲۵ nm than the ones with a diameter of ۵۰ nm. In all cases, there is an acceptable agreement between the results obtained from the mixture and the single-phase models, with discrepancies of less than ۱.۱۳%.

کلیدواژه ها:

CFD simulation ، Carboxymethyl cellulose ، Non-Newtonian nanofluids ، entrance region ، Convective heat transfer