Flow And Heat Transfer Characteristics Analysis And Design Optimization Of Stirred Tank Bioreactor

The stirred tank bioreactor is widely used in biochemical production such as fermentation and cell culture due to its advantages of simple structure,easy operation,and good mixing.Agitator is an important part to realize the mixing operation in the kettle.Its role is to make the materials in the kettle mix evenly and promote the heat transfer in the kettle through mixing.Inadequate material mixing or uneven temperature distribution will lead to low production efficiency.Due to the inability to obtain the complex flow field and temperature field in the kettle,the current design or selection of agitator is often based on experience,In actual production,there is often a phenomenon where the mixing effect is not ideal due to the unreasonable selection of agitators.Therefore,it is necessary to conduct research on the heat flow multi field coupling of the mixing kettle and optimize the design of the mixing equipment.The main research content is as follows:According to the design manual,a preliminary structural design was carried out for the agitator used in the Escherichia coli fermentation tank.Based on the heat flow coupling theory,suitable turbulence models and rotating blade treatment methods were selected,and numerical simulation methods were developed.To verify the effectiveness of the simulation method,the same model as in published literature was established for numerical simulation,and the simulation results were compared with experimental results.The error between the calculation results and experimental results was small.Firstly,by changing the impeller diameter and blade inclination angle,the macroscopic flow field and temperature field in the kettle under different impeller diameters and inclination angles,as well as the velocity component distribution on each sampling line,are analyzed to study the influence of agitator design parameters on the flow and heat transfer characteristics in the kettle.The results show that the maximum flow velocity and high-speed area inside the kettle increase with the increase of the impeller diameter.The radial flow characteristics of the lower impeller are more obvious,and the axial mixing ability is also stronger.As the impeller diameter increases,the overall temperature inside the kettle increases significantly,and the high-temperature area inside the kettle also increases.The stirring power is proportional to the impeller diameter;Changing the inclination angle does not affect the maximum flow rate inside the kettle,but it will change the distribution of the flow field inside the kettle.The maximum temperature and power inside the kettle increase with the increase of the blade inclination angle.Secondly,by changing the distance between the lower impeller and the layer spacing,the macroscopic flow field and temperature field inside the kettle,as well as the distribution of velocity components on each sampling line,were analyzed under different distance from the bottom and layer spacing.The influence of agitator process parameters on the flow and heat transfer characteristics inside the kettle was studied.The results show that the radial flow characteristics generated by the lower impeller are more obvious as the distance from the bottom increases.The highest temperature inside the kettle decreases with the increase of the distance from the bottom,and the temperature gradient inside the kettle increases with the increase of the distance from the bottom;The layer spacing does not change the maximum flow rate in the kettle,but will affect the flow field distribution between the blades and above the kettle body.If the layer spacing is too large,the fluid between the blades will be stratified,which is not conducive to the fluid mixing between the two oars.The maximum temperature in the kettle increases with the increase of the layer spacing,and the temperature distribution in the kettle also becomes more uniform with the increase of the layer spacing.Finally,based on the principle of orthogonal experiment,a four factor and four level orthogonal table was designed,and the influence weights of each factor on various performance indicators in the kettle were analyzed using the range method.The optimal parameter combination was ultimately selected: propeller diameter 130 mm,inclination angle 75°,bottom distance 80 mm,and layer spacing 190 mm.The results were compared with the initial design,and the feasibility of the optimization was verified.The research results can provide theoretical guidance for the structural design optimization of stirred tank bioreactors.Figure [49] Table [11] Reference [67]...