Numerical investigation of the effect of nanofluid and obstacle use on heat transfer in a developing pipe flow

In this study, the flow and heat transfer characteristics of nanofluids, which are widely used today, in a pipe were investigated. For this purpose, a numerical study was carried out under developing flow conditions in a circular pipe with a diameter of 5 mm and a length of 30 mm. The pipe is heated by a constant heat flux through its upper wall. Water or equal proportions of ethylene-glycol-water mixture was used for the base fluid forming the nanofluid used as the working fluid. Al2O3, TiO2, MgO and CuO were used as nanoparticles in volumetric mixing ratios up to 4%. At the same time, in order to investigate the effect of nanofluids on heat transfer, single and multiple barriers in semicircular geometry were placed inside the pipe. By comparing the differences in thermophysical properties of base fluids and nanofluids, the effects of nanofluids on heat transfer were observed. The change in the entropy of the working fluid under the specified conditions was also investigated. It was observed that the entropy decreased as the heat transfer from the upper wall to the outside increased. In the light of this information, it has been determined that the entropy of nanofluids is lower than the entropy of base fluids. In this thesis study, it was determined that the velocity values of the base fluid and nanofluid in the pipe did not change. However, it was determined that the velocity values of the base fluid and nanofluid changed significantly when obstacles were added to the upper and lower walls of the pipe. Since the heat flux is applied along the upper wall of the pipe, it has been observed that the temperature and entropy values do not change along the lower wall, while the temperature and entropy values increase along the upper wall of the pipe. It was determined that the temperature and entropy reached their maximum values at the top of the pipe outlet. It was observed that the stream function value reached the maximum values along the upper wall of the pipe. In addition, the stream function of the nanofluid was greater than the stream function of the base fluid. In addition, the nusselt number of nanofluid was minor than the nusselt number of base fluid. At the same time, the heat transfer coefficient of the nanofluid was higher than that of the base fluid.