Abstract:
In this research, the effect of Al2O3/water-based nanofluids on the heat transfer enhancement in heat exchangers with rotating straight inner tube was examined. Nanofluids including Al2O3 nanoparticles with 0.25 and 0.5% volume concentrations and pure water as a base fluid were obtained. The aim of the study is to experimentally investigate and compare the influence of straight inner tube on the performance of a double-tube heat exchanger at different flow rates, different capacity ratios (0.25, 0.5, 0.75, 1), different speeds of rotation (0 rpm, 100 rpm, 150 rpm, 200 rpm, 300 rpm, and 500 rpm) and by using the Al2O3/water-based nanofluid at volume concentrations of nanoparticles 0.25 and 0.5%. In the experiments for straight tubes, the flow is turbulent. In order to determine the heat transfer enhancement, the experimental data were compared for pure water and nanofluids. According to the results, the Nusselt number, pressure loss, and efficiency of heat exchanger were measured. The validation of the experimental results was proved by plotting the graphs of Nusselt numbers versus Reynolds numbers for nanofluids having various volume concentrations. From the experiments, the correlations for Nusselt number were obtained and experimental results were compared with the literature data by drawing graphs. In the experiments using nanofluids, their thermal performance increased considerably compared to pure water. The experiment that provides the best increase in heat transfer is that using the Al2O3/water-based nanofluid with 0.5% volume concentration at the speed of rotation 300 rpm. © 2021 by Begell House, Inc.