simulation of Single-phase and two-phase flow of water-titanium oxide nanofluids in a double-tube counter flow heat exchanger and Investigation of heat transfer and pressure drop

In this study, the simulation of water-titanium oxide nanofluid has been done in a double-tube counter flow heat exchanger with constant heat flux by Fluent software. The main purpose of this study is to compare single-phase and two-phase mixed model with experimental results to obtain the best simulation model. The results show that The Nusselt number and Heat transfer coefficient for a 0.2% volume fraction for Reynolds number more than 8000, the single-phase model is closer to the experimental results than the two-phase model, but for Reynolds lower than 8,000, two-phase mixed models are in good agreement with experimental results. The comparison of the dropping pressure shows that the faster the speed of Nanofluid is increased, the greater is the difference between the simulation and the experimental results. The results show that the highest increase in Nusselt number and Heat transfer coefficient is seen in higher Reynolds numbers, which indicates that in the high Reynolds numbers, the increase in volume fraction is more effective, one of the reasons is that homogeneity of Nanofluid in higher Reynolds is due to more turbulence. In general, it can be said that the results of the simulation are in good agreement with experimental results.