| Bioreactor is the key equipment of animal cell culture,and the efficiency of cell culture depends on the flow field characteristics of the fluid in the bioreactor.Shaking bioreactor is a new type of bioreactor developed in recent years.The culture medium shakes periodically in the bioreactor,the shear strain rate of the overall flow field is low,which is especially suitable for cell culture.However,compared with the traditional stirred bioreactor,the mixing and dissolving oxygen performance of the shaking bioreactor is worse.Baffles are installed in shaking bioreactor is an effective way to improve mixing and dissolving oxygen performance.This paper presented four kinds of novel baffle structure,such as rectangular baffle,arc baffle,single-helical baffle and double-helical baffle,studied the flow characteristics of shaking bioreactor with baffles by the method of computational fluid dynamics,and analyzed the influence of geometric parameters of baffles on the fluid flow characteristics in the bioreactor.The main research work and results of the paper are as follows:(1)A shaking bioreactor model with a conical bottom was established.The RNG k-?double equation model was used to simulate the turbulence in the bioreactor,and the VOF(Volume of Fluid)model was used to track the gas-liquid interface.The moving grid model was used to realize the motion law of the bioreactor wall.The flow state of the unbaffled bioreactor under different working conditions was simulated and analyzed.Compared with the experimental results,it could found that the liquid level height and the shape of the liquid surface basically matched and the overall change law was similar,which verified the reaction established in this paper.(2)The flow characteristics of the shaking bioreactor with no baffle,rectangular baffle and arc baffle with rated volume of 50 L were compared by numerical simulation,and the effects of different baffle widths and numbers on the flow characteristics were studied.It was found that the rectangular and arc baffle structures can significantly improve the mixing and dissolving oxygen performance of the bioreactor.With the increase of baffle width and number,the turbulent dissipation rate?and the oxygen mass transfer coefficient per unit volume k_La of the rectangular and arc baffle bioreactors both showed an increasing trend,which was favorable for mixing and dissolving oxygen.On the other hand,the average shear strain rate of the bioreactor also increased with the increase of baffle width and number,which also increased the damage to cells.(3)Through numerical simulation analysis of flow characteristics of rectangular baffle and arc baffle bioreactor with different baffle widths and numbers,it was found that the turbulent dissipation rate?and the oxygen mass transfer coefficient per unit volume k_La of the rectangular baffle bioreactor were both greater than that of the arc baffle bioreactor,that is,the mixing and dissolving oxygen performance of the former was better than that of the latter.However,in terms of shear performance,the average shear strain rate of the rectangular baffle bioreactor with different baffle widths and numbers were greater than the range suitable for the growth of CHO cells,while the average shear strain rate of the arc baffle bioreactor did not increase significantly and was still within the range suitable for the growth of cells,so it was the preferred structure of the bioreactor.(4)The influence of the helical baffle structure on the flow characteristics of the bioreactor was studied.Compared with the unbaffled bioreactor,the turbulent dissipation rate?of the single-helical baffle bioreactor and double-helical baffle bioreactor increased by 230%and 544%respectively,and the oxygen mass transfer coefficient per unit volume k_La increased by 87.1%and 152%respectively.In other words,the mixing and dissolving oxygen performance of the helical baffle bioreactor was greatly improved.The average shear strain rate of single-helical and double-helical baffle bioreactor was higher than that of unbaffled bioreactor.According to the comparison of mixed,dissolved oxygen and shear properties,the double-helical baffle structure is superior to the single-helical baffle structure. |
PDF Full Text Request