PCM in a Triplex Tube with Internal-External Fins: Paper Validation

PCM Melting in Triplex Tube with Internal-External Fins, Paper Numerical Validation, CFD Simulation by ANSYS Fluent

Description

This project simulates the melting process of a phase change material (PCM) within a triplex tube fitted with internal and external fins, using ANSYS Fluent. The simulation is based on the reference article "Enhance heat transfer for PCM melting in a triplex tube with internal-external fins," with results compared and validated against the paper's published data.

The simulation is performed in two dimensions, modeling only a hollow circular cross-section of the pipe. The geometry features 4 rows of outer fins connected to the pipe's inner diameter wall and 4 rows of inner fins connected to its outer diameter wall, with both walls and their respective fins made of copper. The PCM used inside the tube is RT-82, defined with an initial density of 770 kg/m³ under the Boussinesq model, a specific heat capacity of 2000 J/kg·K, thermal conductivity of 0.2 W/m·K, and viscosity of 0.03499 kg/m·s.

The 2D geometry was designed in Design Modeler and meshed in ANSYS Meshing using a structured grid totaling 17,856 elements.

Methodology

Since the objective is to track the evolving solid and liquid phase regions as melting and freezing progress over time, the Solidification and Melting model was applied. This model was configured with a solidus temperature of 70°C (the maximum temperature at which the material remains fully solid) and a liquidus temperature of 82°C (the minimum temperature at which it becomes fully liquid), along with a latent heat of fusion of 176,000 J/kg for the pure PCM.

Both the tube's inner wall with its outer fins, and the outer wall with its inner fins, were held at a constant temperature of 90°C, while the PCM inside the tube started at an initial temperature of 27°C. Given the goal of tracking the PCM's melting behavior over time, the simulation was run as unsteady (transient).

Conclusion

Results were compared directly against the reference paper using Figures 7 and 13, which track the PCM's average temperature over time and the liquid mass fraction resulting from melting over time, respectively. This comparison specifically corresponds to the paper's case where the PCM is influenced simultaneously by both the internal and external fins — with the present CFD results showing close agreement with the article's reported values across this comparison.

Additional 2D contours of pressure, temperature, and liquid mass fraction were extracted at multiple points throughout the transient simulation, capturing how the melting front and internal temperature distribution evolve over time as the PCM transitions from solid to liquid under the combined influence of the internal and external fin arrangement.