Study On Flow Characteristics And Heat Transfer Under Flow Fluctuating Conditions

In this thesis, the study on pulsatile turbulent flow in a pipe was carried out using computational fluid dynamics (CFD). The simulation used CFX commercial software to investigate the flow characteristics and heat transfer for single phase water flow. The standard k-εmodel was used for the simulation.The CFD results for steady flow agrees well with classic correlations such as the Blasius correlation and the Dittus-Boelter correlation.The numerical simulation results are also compared with experimental results for unsteady flow in heated and non heated pipe.The simulation parameters such as the average velocity, the velocity amplitude, heat power and fluid temperature are calculated from the experimental data and input in the CFX software. The comparison shows similarity for the study of the pressure drop and shows that there is a phase difference between experimental and simulation results.The results for convective heat transfer coefficient don't agree with experimental, to explain this difference the comparison with the Dittus-Boelter correlation was proposed, it shows that the simulation and Dittus-Boelter correlation agree well.The influence of increasing the heat power, the period and the amplitude of the flow on the flow characteristics, convective heat transfer coefficient, Nusselt number, wall temperature, and cross-sectional fluid temperature are investigated by numerical simulation.The results show that the flow characteristics and heat transfer coefficient oscillate periodically with the same inlet velocity period. The changes of the period of the velocity don't affect the friction factor and the Nusselt number but the increase of the velocity amplitude and average velocity increase theme.The increases of the heat power don't affect the flow characteristics and the convective heat transfer coefficient.