Study On Heat Transfer And Mass Transfer For Multiple Impellers In Pseudoplastic Fluid With High Viscosity

Pseudoplastic fluid with high viscosity is a kind of common in most productionand living, which has a shear thinning characteristic. It is more difficult for mixing,oxygen transfer and heat transfer of pseudoplastic fluid than Newtonian fluid in theindustrial production process. The degree of mixing affects product quality andproduction efficiency. Therefore, how to strengthen the mixing of pseudoplastic fluidwith high viscosity becomes an important part of current research. Despite itsimportance, the domestic and foreign research is relatively few in the gas-liquid-solidthree phases system. Xanthan gum fermentation process is the typical processinvolving the mixing of pseudoplastic fluid with high viscosity. The viscosity offermentation broth gradually increase with fermenting and the fermentation brothshow characteristics of pseudoplastic fluid. Duo to the aerobic fermentation process,supply of oxygen and heat removal in the reactor has a great influence on the qualityand yield of fermentation products. So it’s significant to empolder the mixing systemthat meet the above technological requirements.Previous studies prove that for maximum blade impeller (abbreviated as MB), itis apparent than others in mixing and oxygen transfer, but the installation problem ofheat exchange system cannot be solved in the actual amplification process. Therefore,in this paper, smaller size standard turbine impeller (DT1), improved turbine impeller(DT2), and axial flow impeller A315are combined into different types of multipleimpellers. In the cold reactor, the influence that speed and aeration rate have influenceon oxygen transfer coefficient, heat transfer coefficient, power consumption andtemperature distribution under the multiple impellers are studied, in order todetermine the combining form of multiple impellers suiting high viscosity fluid’smixing, heat transfer and mass transfer, and facilitating the reactor amplification.The results show that for heat and oxygen transfer coefficient, they are affectedby axial impeller action mode and size of turbine paddle. In terms of axial impelleraction mode, for DT1+A315+A315(up), it is apparent than DT1+A315+A315(down)in the heat transfer coefficient, but DT1+A315+A315(down) is superior to DT1+A315+A315(up) in oxygen transfer coefficient. In terms of turbine paddle size,A315+DT2+A315is apparent than A315+DT1+A315in heat transfer coefficient, butA315+DT1+A315is superior to A315+DT2+A315in oxygen transfer coefficient.Overall, the A315up action mode and turbine paddle with small disc diameter canpromote heat transfer. The A315down function mode and turbine paddle with largedisc diameter can promote oxygen transfer.In aspect of oxygen and heat transfer, A315+DT1+A315is significantlyapparent than MB in the condition of same PVby contrasting the experimental data ofmultiple impellers and MB, such as oxygen transfer coefficient, heat transfercoefficient, and power consumption. It indicates that in terms of heat and oxygentransfer, multiple impellers can precede MB by reasonable arrangements for multipleimpellers combining form. Multiple impellers can be used in the reactor amplificationprocess. The results have a certain reference value for the mixing study of otherpseudoplastic fluid with high viscosity.