heat transfer analysis of nanofluid flow on elliptical tube bundle with different attack angles

Flow of aluminum oxide/water nanofluid is numerically investigated in a heat exchanger at different densities of solid nanoparticles and reynolds numbers. the behavior of heat transfer in laminar flow of single-phase nanofluid are explored at various volume fractions of oxide aluminum (0%, 2%, 4%, 6%) and reynolds numbers (5, 15, 25, and 40) using a finite volume method. the main purpose is to study the flow behavior of nanofluid and its heat transfer in a shell and tube heat exchanger with tube banks of the elliptical cross-section with different angles of attack. the results of this study indicate that an increase in the velocity of flow enhances the heat transfer coefficient, resulting in a more uniform temperature distribution. in addition, increase of angle of attack leads to a higher velocity of the fluid flow between the tubes. at higher reynolds numbers, more remarkable entropy reduction is observed with increasing nanoparticle volume fraction. depending on its volume fraction, addition of solid nanoparticles at a constant reynolds number amplifies the flow velocity components and reduces the temperature gradient. the nusselt number can increase up to 17% in reynolds number of 5 for all tube banks depending on the volume fraction and angle of attack, which is up to 23% for re = 40. therefore, the amount of shell-side friction coefficient increases by 25 to 35% for re = 5 to 40. for all designs, the increase in the friction coefficient due to angle of attack is less important than the variations of nanofluid volume fractions.