Investigation the effect of various factors in a convective heat transfer performance by ionic liquid, ethylene glycol, and water as the base fluids for Al2O3 nanofluid in a horizontal tube: A numerical study

The present research investigates the heat transfer enhancement by adding alumina nanoparticle to water, Ethylene glycol, and 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtSO4] ionic liquid (called ionic liquid-based nanofluid or INf in synonym) as a base fluid. A horizontal tube with constant heat flux was modeled in two-dimensional geometry with a diameter and length of 4.0 mm and 6.0 m, respectively. Al2O3 (20 nm in diameter) nanoparticles added to the base fluid in 0.5, 1.0 and 2.5 weight fraction percent. Various factors such as Reynolds number, nanofluids concentration, type of base fluid, and especially fluid inlet temperature studied in this research. Impressive results observed with variation in fluid temperature which for the temperature below room temperature (278.15 K) IL-based nanofluid shows greater heat transfer coefficient than water and Ethylene glycol-based nanofluids because of its higher thermal conductivity and viscosity at a lower temperature. And also, by adding nanoparticles to the base fluids and increasing the concentration of nanofluids, the heat transfer coefficient increased. Both the maximum heat transfer coefficient and heat transfer enhancement observed for IL-based nanofluid at 2.5 wt% concentration of nanoparticle. Finally, a correlation proposed for Nu number that satisfies for all studied nanofluids with R-2 = 0.971 and AREP = 7.9%.