(122e) In-Silico Investigation of Temperature-Controlled Bioreactors

The design and optimization of bioreactors are critical for efficient and cost-effective production processes. Numerical simulations play a crucial role in predicting the behavior of these complex systems. In contrast to experimental investigations of stirred tanks, computational analysis offers high-resolution spatial data, rapid analysis of different internal geometries, and applicability to different reactor scales once validated. Improving the accuracy and efficiency of current models and schemes will accelerate the optimization process of bioreactors and reduce the need for laboratory tests.

The dynamic behavior of large temperature-controlled tanks can be of particular interest since the integrity of the production process can be highly temperature sensitive. An accurate prediction of the thermal state within the reactor is a key insight in order to avoid local temperature hotspots [1]. In our project, a state-of-the-art implementation of the lattice Boltzmann method is used to simulate the fluid flow and the heat transfer in a jacketed stirred vessels for biopharmaceutical fermentation. Both the lattice Boltzmann framework as well as the transport scheme for thermal energy can utilize advances in graphical processing units (GPUs) and therefore ensure fast execution times due to the high degree of parallelization.

These models then simulate the separate flows of the liquid within the stirred vessel and the heat transfer medium within the jacket. The heat transfer through the jacket is modelled with thermal wall functions and therefore accounts for the resistance on both sides. A large eddy scheme is applied for turbulence. The results are validated with experimental data of lab-scale reactors at different flow conditions and show a promising agreement for large scale design processes, both qualitatively and quantitatively. The results are also compared with multiple Nusselt-correlations.

In addition, the simulation of both fluid flows enables a separate analysis of the flow conditions within the vessel and the jacket like the inlet velocity or inlet temperature during the heating and cooling procedure. Different flow conditions in the outer heating jacket are analyzed and how they affenct the overall time required for heating and cooling of the media inside the stirred vessel.

[1] Cummings, Cody M. et al. “Transient thermal modeling of bioprocess equipment”, International Journal of Heat and Mass Transfer 184, 2022, 122064