Studies of Fluid Flow and Performance of Spinning Disk Reactor

Author:Wu Xiang Sen

Supervisor:chen jian feng


Degree Year:2018





Spinning disk reactor(SDR),known as one kind of chemical equipment for process intensification(PI),produces the high centrifugal field via the rotational disk.Under the centrifugal field,the liquid is quickly spread on the surface of rotating disk and a liquid film is generated.The rapidly shear of liquid film accelerates the surface renewal of the liquid film on the disk surface,which intensifies the mass transfer and heat transfer.The SDR has been wildly applied in material preparation,catalytic reaction,polymerization reaction,and biodiesel preparation.The rotating disk is the corn component of SDR,and the liquid distribution and flow pattern are influenced by the micro-structure of disc surface.The development of surface treatment technology and nanostructure processing technology make it possible to produce novel rotating disks.These novel rotating disks not only improve the character of application,but also enlarge the area of applications.In this work,firstly,nano-,micro-,hydrophobic structure was built on the surface of rotating disk by electrostatic spraying technology;secondly,high speed camera system and Computational Fluid Dynamics(CFD)was applied to observe the hydrodynamic in SDR;thirdly,iodide-iodate system was introduced to study the micromixing in SDR;finally,SO2-NaOH mass transfer system was also introduced to investigate absorption rate of SO2 and mass transfer coefficient.The whole work is summarized to give the flowing points:1.Electrostatic spray technology was applied to construct the hydrophobic surface of stainless steel disc.The contact angle was increased from 70.6° to 115.6°.A high speed camera system was introduced in observing the liquid flow in SDR.On the hydrophobic surface-modified spinning disk(OSD),high viscosity liquid makes the area-equivalent radius(Rm)changing sharply by the changes of rotating speed.The smaller liquid surface tension contributes to the liquid spreading on the surface of OSD.In the cavity zone of SDR,four different flow pattern(droplet-ligament,ligament,ligament-film,and film flow)were identified by observing the liquid film on the edge of disk.The increase of disk rotating speed and liquid flow will contribute to the transition of liquid film flow pattern.Reducing the surface tension of the liquid decreases the critical liquid volume flow of the liquid film flow and increasing the viscosity of the liquid increases the critical liquid volume flow of the liquid film flow.In the cavity zone,the diameter of liquid droplet increases with increase of rotating speed and liquid viscosity,while the diameter of liquid droplet decreases with the decrease of liquid surface tension.The liquid flow rate influents the quantity of droplets,while it does not influent the droplet diameter.The droplet diameter generated by OSD is slightly larger than generated by non-modified spinning disk(NSD).The distribution of liquid droplet size agrees well with R-R distribution.Distribution index m ranges from 4.78 to 6.81,and it increases with the increase of rotating speed,increase of viscosity,and decrease of surface tension.Average liquid speed u and average radial speed ur increase with the increase of rotating speed,while the liquid flow rate,viscosity,and surface tension does not influence liquid average speed u and average radial speed ur · The empirical correlation of liquid average diameter and velocity is obtained and its relative error is less than 15%.2.A 3D CFD simulation with Large eddy simulation(LES)model and Volume of fraction(VOF)model was applied to predict the liquid flow on the surface of rotating disk.The simulation result shows the liquid film on the disk surface consists of inlet zone and turbulent zone.The predicted radius(Rm)of liquid film is agreed with the experimental results.The average relative errors between simulated and experimental Rm is 15%.3.CFD was applied into optimization of pre-mixing distributor in SDR.The best optimized result is that solution A is fed in tangential mode(T-mode)and the distance of solution B outlet and entirely solution outlet is 15 mm.There exists a best operation condition in hydrophobic surface-modified spinning disk reactor(OSDR),while it is not sure whether there exists the best operation conditionin non-modified spinning disk reactor(NSDR).The micromixing time of NSDR and OSDR was calculated by the agglomerating model.SO2-NaOH mass transfer system was introduced in investigating the absorption rate of SO2 and mass transfer coefficient in SDR.The highest absorption rate of SO2 is 95.98%.In addition,an empirical correlation of mass transfer coefficient(KGa)was built based on the experimental data.