Contact UsDiscover how FreeFlow and EnSight can work together to simulate and visualize the cooling of hot fluid in a stirred tank, from detailed heat transfer at the walls to realistic fluid dynamics visualizations.
Thermal-Fluid Challenges in Stirred Tank Cooling
Understanding how hot fluids cool down when in contact with cold walls is a typical thermal-fluid problem, yet it becomes complex when turbulence, mixing, and transient heat transfer are involved. In a stirred tank with hot water introduced into the domain, the cooling process depends on the interaction between the bulk fluid and the cooled tank walls, which are maintained at a constant temperature of 32 °F (0 °C). Efficiently capturing the evolving fluid temperature, turbulent mixing, and wall heat flux requires advanced simulation and visualization tools.
Engineering Solution: Ansys FreeFlow and EnSight
To explore this scenario, Ansys FreeFlow, a Smoothed Particle Hydrodynamics (SPH) tool, is used. SPH is well-suited for multiphase and free-surface problems, making it effective for simulating fluid mixing and heat transfer in stirred tanks. FreeFlow provides a meshless approach to modeling free-surface flows and is fully supported by GPUs, enabling fast runs. In this simulation, we introduced hot water at 194 °F (90 °C) for 4 seconds and allowed it to cool through the tank walls with the aid of an impeller to promote mixing.
Analyzing Temperature and Mixing Over Time
We can evaluate the average temperature calculated across all SPH elements. Here, we can see the impact of stopping the hot water inlet flow at 4 seconds and allowing the fluid to cool. Time-plotting tools can be used for a variety of relevant features, including velocity, position, turbulent viscosity, mass, density, and even custom-defined features.
The temperature distribution across SPH elements can also be visualized using histograms and cross-plots. A cross plot allows us to relate two variables. Here, we can see that near the bottom of the tank, temperatures are lower at 10 seconds into the simulation.
Multiple plots can also be combined using the Multi Time Plot option. Here we see that mixing drops significantly once the inlet stops, suggesting that the angular speed or tank geometry might need better tuning.
Advanced Visualization with Ansys EnSight
For further postprocessing and advanced visualization, Ansys EnSight can be used. Its powerful rendering and data manipulation capabilities allow for deeper insights and a realistic view of the flow. This can be achieved using the SPH Screen Surface node representation by constructing an iso-volume using the SPH elements.
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With Ensight, we can further enhance the post-processing workflow by evaluating the influence of key parameters on mixing behavior and heat transfer in the fluid. These are some of the features we can look at:
- Temperature distribution throughout the tank.
- Velocity profile across the fluid
- Turbulent viscosity fields, which reveal how turbulence affects mixing and heat transfer.
A detailed YouTube video is available below, demonstrating the step-by-step setup of this model and the post-processing procedures in FreeFlow and EnSight.
Benefits of FreeFlow and EnSight
The combination of FreeFlow and EnSight provides a comprehensive framework for both simulating and interpreting cooling in stirred tanks.
- FreeFlow captures the physics of fluid–wall interaction, ensuring that heat transfer and mixing phenomena are accurately represented.
- EnSight enhances the analysis with advanced visualization, enabling engineers and researchers to create high-quality visuals of fluid surfaces and investigate the effects of key parameters on performance.
Together, these tools offer a complete workflow—from simulation to visualization—allowing researchers and engineers to study and optimize heat transfer processes in stirred tanks with confidence.
Interested in getting started with Ansys FreeFlow? SimuTech Group recently hosted a hands-on FreeFlow workshop covering SPH fundamentals and simulation setup. Our CFD consulting team can also help you apply FreeFlow and EnSight to your mixing and heat transfer challenges. Contact us to learn more.
