Investigation On The Flow And Mixing In Millimeter Cross Flow Channels

Investigation on Fast Flow(FF)and mixing in the various confined mil-limeter Cross Flow(CF)channels was carried out by using Laser Induced Fluorescein(LIF)and Particle Image Velocimetry(PIV).The experimental study of the fast mixing behavior in the millimeter cross flow mixer provides basic data for further numerical simulation works.Assembling of the millimeter channel PMMA board technique was pro-posed and the completed board successfully passed tests for resilience under the fast streaming flows and pressure.Experimental analyses have been performed on mixing channels with chamber dimentions 1 × 1 × 1 mm,3 × 3 × 1 mm,5 × 5 × 1 mm,and 7 × 7 ×1 mm,length × width × height respectively,in order to investigate the depend-ence of the mixing efficiency on chamber enlargement.It has been noticed that at higher Reynolds numbers in wider chambers more fluid gets trapped and stagnates as the path lines of the flow attains certain pattern.Stagnation time of the flow in wider chambers increases without adding significant inter-face surface to achieve better mixing at the initial sector.The 3 × 3 × 1 mm chamber channel in the stratified mixing regime showed almost no difference in increasing diffusion time over the simple T-shaped 1 × 1 × 1 mm chamber channel.The vortex mixing regime appears at 4.5 m/s in the 5 × 5 × 1 mm chamber channel.Increase in the flow velocity over 6 m/s causes formation of vortexes at the entrance to the mixing channel from the chamber.At that point,the mean velocity becomes too high in the middle of the mixing channel and streaming flow field scrapes the edges of the transition wall of the mixing channel.The experimental results show that the flow velocity measured by PIV is in good agreement with that estimated by flow rate.In the impact zone,the velocity distribution is the same as that at the end of the mixing channel.This means that although the length of the mixing channel is 170 mm,due to the friction and collision of two streams of fluid in the mixing channel,the fluid does not slow down significantly.This phenomenon appeared in the images obtained by the simulation works under the same conditions for the flow field.The CFD method is used to simulate and verify the flow and mixing characteristics in the cross flow channel.The CFD model and numerical method with accurate and reliable results are established.Numerical results are obtained in 2D and 3D versions in order to have a better insight to the fluid behavior in the millimeter channel at higher Reynolds number.By using the validated CFD model and method,the numerical simulation of flow and mixing characteristics in millimeter cross flow channel under various geometric structures and operating condi-tions is carried out,and the structural parameters and operating conditions of optimal design are proposed,which provides a reference for the design of such industrial reactors.