Phase Change Material (PCM) in a Finned Tube, ANSYS Fluent CFD Simulation Training

Description

The present issue deals with the simulation of PCM using ANSYS Fluent software. We perform this CFD project and investigate it by CFD analysis.

Thermal energy storage in PCM is obtained during the phase change process, so that during the phase change from solid to liquid, it absorbs heat from the environment and during the liquid-to-solid phase change, returns heat to the environment.

PCMs have a variety of melting (Liquidus) or freezing (solidus) temperatures and are therefore used in cooling and heating systems; These materials receive solar energy in the form of latent heat and melt on warm days, and then return the heat to the environment again in the cool night, by changing the phase and solidification and melting process.

PCMs are embedded in a three-layer tube heat exchanger as a latent heat storage tank; The inner tube body and its fins are made of copper which has good Thermal Conductivity and the fluid in the inner tube is liquid silicone type and also the PCM is Erythritol.

Since the nature of the PCMs of the present model is based on the phase change between the two solid and liquid phases, a Solidification and Melting module is used for CFD simulation. The simulation process is performed over 12,000 seconds.

The purpose of the present study is to investigate the fluid and thermal behavior of the phase change materials and the fluid mass fraction in the solid-liquid mixture, based on the dimensions and physical conditions of the tube fins as well as the properties of the internal fluid.

Incoming fluid flow has a velocity of 1 m/s and a temperature equal to 343.15 kelvin. Outer walls are considered with a heat flux of 0 and inner walls are considered as coupled walls automatically by the software.

The 3-D geometry of the model was designed by Design Modeler software. To mesh the present model, we have used ANSYS Meshing software and Hybrid (structured and unstructured) mesh. The element number is 107718.

Phase Change Material Methodology

After the activation of the solidification and melting module, new thermal properties for the fluids defined in the problem will be activated, as mentioned in the table above.

Since the melting and solidification process takes place within the Erythritol material as PCM, it has a point of melting and solidification temperature as well as the latent heat rate of melting, which is a major factor in the melting and solidification process.

But while the silicon liquid does not play a role in the phase change model process, it’s melting and solidification points are equal to zero with a latent heat rate.

Phase Change Material Conclusion

At the end of the solution process, two-dimensional contours related to the temperature and mass fraction of the liquid are obtained. These contours are obtained at the time of the last second of the simulation process, the 1200s.

The contours show well that with the passage of time and the melting of the PCM material, the heat transfer has taken place well and the temperature in the center of the tubes has risen.