The numerical investigation of angle of attack of inclined rectangular rib on the turbulent heat transfer of Water-Al2O3 nanofluid in a tube

In present research, the flow and heat transfer characteristics of the turbulent flow in the tube have been numerically investigated. The main purpose of this study is investigating the effect of attack angle of ribs and Al₂O₃ nanoparticle on the heat transfer enhancement. The flow has been simulated in Reynolds numbers of 24000, 36000, 48000 and 60000 in volume fractions of 0, 2 and 4% of nanoparticles. In present study, in order to ensure from the accuracy of numerical solving procedure, the obtained results have been compared with others empirical and numerical results and proper coincidence has been obtained. The mean Nusselt number, pressure drop and performance coefficient are presented results. In addition to the mentioned quantitative results, in order to investigate of physics of flow, the stream lines, are also presented. The obtained results demonstrate that, the existence of ribs with the creation of eddy on the direction of flow causes better mixture of flow and consequently, heat transfer increases and adding nanoparticles to the base flow causes more augment of heat transfer. According to the obtained results, in order to improve the heat transfer without considering the applied pressure drop, using rib with angle of attack 90° inside the tube is suggested. However, the investigation of fluid- thermal performance coefficient indicates that, the ratio of heat transfer enhancement to the applied pressure drop in the rib with attack angle of 60° is maximum.