(152a) Computational and Experimental Investigation - Impeller Effects on Heating Times in a Dimple-Jacketed Stirred Tank

Process media in agitated vessels are commonly heated or cooled via heat exchange with a utility fluid in the vessel jacket. Agitation influences heat transfer through homogenization and enhanced convection at the vessel wall. While standard correlations exist for estimating heat transfer coefficients and process times, advanced Computational Fluid Dynamics (CFD) methods offer the potential for more detailed predictions, provided they are validated against reliable experimental data.

This work presents the completed results of an investigation comparing laboratory experiments with M-Star CFD predictions for heating in a jacketed agitated vessel. Building on preliminary findings, this study includes a more complete analysis of the experimental data, including a new statistical review, and incorporates a more detailed CFD model of the jacket-side heat transfer. Laboratory experiments measured heating times for 21 gallons of water in an 18.1-inch diameter, dimple-jacketed stainless steel vessel agitated by three distinct impellers: a narrow hydrofoil (A310), a Rushton turbine (R100), or a 4-bladed 45° pitched blade turbine (PBT, A200). Transient measurements of water temperature, oil temperatures, and oil flow rate were recorded.

These comprehensive experimental results are directly compared against M-Star CFD simulations employing the lattice Boltzmann Large Eddy Simulation (LES) solver. The simulations model transient flow and thermal fields in both process and jacket fluids, including the vessel wall, and utilize the generalized method for estimating convective heat transfer coefficients based on local conditions near the wall (Thomas et al., 2024). This direct comparison across different impeller types serves to experimentally assess the generality, validity, and capability of the CFD approach for predicting heating dynamics, moving beyond validation against empirical correlations alone. The comparison focuses on time-resolved temperature profiles and overall heating times, providing insight into the model's accuracy in capturing the impact of impeller selection.

Thomas, J. A., DeVincentis, B., Janz, E., & Turner, B. (2024). A general approach for predicting convective heat transfer coefficients in turbulent systems. International Journal of Heat and Mass Transfer, 220, 124989. https://doi.org/10.1016/j.ijheatmasstransfer.2023.124989