PIV Experimental Study On The Characteristics Of Non-Newtonian Fluid In Wavy-walled Tubes For Pulsatile Flow

The problems associated with energy shortage and environmental pollution are the main important issues accompanying the rapid development of industry.Improving energy utilization is of great significance for protecting the environment and reducing energy demand.Much more importantly,optimizing the heat and mass transfer equipment is an effective measure to enhance the mass transfer enhancement efficiency.To our knowledge,pulsatile flow is widely used in the process of heat transfer enhancement as a perturbation technique.Then,we investigated the flow characteristics of a non-Newtonian fluid(CMC solution)in different wavy-walled tubes in the pulsatile flow field.The object of this study is the flow of CMC solution in wave-walled tubes with different geometric parameters.Under the condition of low net flow Reynolds number,the flow structure of eight equal moments in a pulsating period in a wavy-walled tubes is measured by PIV(particle image velocimetry).The velocity vector diagram and streamline diagram are obtained.Through the analysis of the experimental results of the two groups,the influence of the geometrical size and the St are obtained on the flow and mass transfer in the wavy-walled tube.Experimental results show that: 1,the wavelength of the wavy-walled tube has little effect on the flow state in the pulsatile flow,but the amplitude has obvious effect.The greater the amplitude of wave-wall tube,the flow is more complex,and the better mass transfer enhancement.2,the period of the pulsatile flow in the tube is changed under the condition of two vibration rates.Compared with the given experimental conditions,the phase difference of the pulsation period becomes larger with the increase of St number.The phase difference of the large amplitude tube is obviously larger than that small,but the wavelength has no obvious effect on phase shift.3,the unsteady flow in the pulsatile flow field is mostly distributed in the deceleration region.With the change of St the unstable flow does not move,but the pulsation cycle occurs the phase shift by itself.In addition,the flow field with reverse flow is more complex than the no reverse flow,and the mass transfer effect is better.To sum up,the study found that,choosing the appropriate amplitude of the wave-walled tube and the operating parameter St number can enhance the mass transfer in the pulsatile flow field.Besides that,the mechanism of mass transfer enhancement in reverse flow is modified and improved.