Study On Flow Characterisics And Mxing Performances In The Micromixer With Dislocation Sub-channels

In recent years, with the rapid development of microelectronics systems, the demands of theminiaturization in natural sciences and engineering scientific research is increasing. The designand production of the MEMS which composed of micro-pumps、micro-reactors and micro-heatexchanger is facing the challenges of modern technology development. As part of themicroelectronics systems, micro-reator has been widely used in the field of electronic technology,biomedicine, materials science, automotive electronics and clinical medicine, so the pressure ofits is increased. In the study of micro-reator, the question how to achieve rapid mixing betweentwo fluids makes micromixer become one of the current reasearch focus. The passive micromixerbased on the principle of planar asyumetric split and recombine is discussed in this article.Deionized water and ethanol have been used as the working fluids to carry out theoretical studyand experimental verification for flow、mixing and heat transfer characteristics.Firstly, numerical simulations are performed to the flow and mixing characteristics ofasyumetric split and recombine micromixer. The simulations demonstrate that the differentgeometries have significant effects on the mixing performance of the micromixers. On thebasis of asyumetric circular channel, the structure of the major sub-channel between everytwo cycling elements is changed to increase the fluids disturbance and the contact area of thedislocation sub-channel micromixer. The structural optimization are discussed from twoaspects in this article: with the increasing of the dislocation angle, the mixing performance ofthe dislocation micromixer is gradually improved; The mixing performance of themicromixer has a trend decreasing after increasing as the dislocation ratio growing. At thesame time, the entrance flow rate of the fluids has a serious impact on the flow and mixingconditions for the micromixer. Considering little effect between the pressure losses and thedislocation angle, dislocation ratio and Re have been regarded as the dominant factors of themicrochannel pressure drop. Finally, considering totally the influence of various factors, theoptimum dislocation angle is120°and the dislocation ratio is w3/w4=1.Secondly, the study and discussion have been carried out to observe the flow and mixingcharacteristics for the three different structure micromixers. The results show that the internalworking pattern is affected by different sub-channel structures. By changing the fluid flowpattern and increasing the mass transfer between the fluids, the mixing performance of theworking fluids is improved. The mixing effect of the dislocation sub-channel micromixer isthe best and the symmetrical circular channel mixer is the worst when Reynolds number isthe same; The complex channel structure is not only affecting the mixing index of themicromixer but also enlarging the pressure loss, thereby the pressure loss of the dislocationsub-channel micromixer is much larger than the other two types.Thirdly, the experimental chip of the dislocation sub-channel micromixer is made of PDMS and deionized water is used as working fluid in this reaserch. During the experment,one of the entry is deionized water marked by black ink. The expermental results keeps a highdegree of consistency with the numerical simulation under different Reynolds numbers.When the flow rate is changed, the error between the experimental and numerical simulationresults do not exceed5.1%.Finally, as changing the temperature of the entrance flow, the numerical simulation hasbeen carried out to observe the flow pattern、mixing index and heat transfer charavteristics.The simulation results show that when changing the temperature of the inlet flow-deionizedwater, part of the physical characteristics of the working fluids was changed, so the the outlettemperature is different. Transformation temperature of the flows did not change the fluidpattern、tne mixing performance and the pressure loss essentially, and it shows that themixing index is influenced little by the temperature.