(83f) CFD Modeling of Impeller Effects on Heating Times in a Dimple-Jacketed Stirred Tank

Process media in an agitated vessel are commonly heated or cooled through heat exchange with a utility fluid flowing through the vessel jacket. Agitation homogenizes media composition and temperature, and also enhances overall heat transfer through the vessel wall. Existing correlations (e.g., see J.R. Nunhez, Chapter 14, Advances in Industrial Mixing, pp 491-532, John Wiley & Sons, New York, NY, 2016) help estimate heat transfer coefficients (process fluid, utility fluid, and overall) and heating / cooling times. These correlations are based on fluid physical properties, and also fluid behavior as produced by given mixing impeller types.

This work compares laboratory results with M-Star CFD (computational fluid dynamics) predictions. Thomas et al. (Thomas, J. A., DeVincentis, B., Janz, E., & Turner, B., 2024, Int. J. Heat Mass Transf, Vol. 220, p. 124989, Elsevier) introduced the M-Star CFD generalized method of estimating convective heat transfer coefficients using local fluid properties (e.g., viscosity) and operating conditions (e.g., energy dissipation rate) near the vessel wall. While they validated the method against various experimentally derived empirical design correlations, this comparison with experimental data provides greater understanding of the method’s generality, validity and capability.

M-Star CFD simulations and laboratory results are compared while assessing the impact of three different impellers (i.e., narrow hydrofoil (A310), Rushton turbine (R100), or 4-45 PBT (A200)) on heating times for 21gals water in a dimple-jacketed 18.1-inch stainless steel vessel. During each laboratory test, oil flow rate, time, and temperatures (water and oil) were recorded each second. The lattice Boltzmann LES solver in M-Star CFD provides transient flow and thermal field results while modeling process and jacket fluids, and temperature of the separating wall. This enabling comparison of model and measurement, as a function of time, facilitates closer interrogation using predicted and measured temperature profiles.