PCM Melting in Triplex Tube with Internal–External Fins, Paper Numerical Validation

Description

The present problem simulates the process of melting phase change materials inside a Triplex Tube with Internal–External Fins using ANSYS Fluent software.

The simulation is based on the data in the reference article [Enhance heat transfer for PCM melting in a triplex tube with internal-external fins], and the results are compared and validated with the results in the paper.

This simulation is performed in two dimensions and hence, only a hollow circular section of the pipe is modeled.

The pipe has 4 rows of outer fins connected to the inner diameter wall of the pipe and 4 rows of inner fins connected to the outer diameter wall of the pipe; So the material of these inner and outer walls, as well as their fins, is made of copper.

Inside the tube, the phase change material is RT-82. So it has an initial density of 770 kg.m-3 in the Boussinesq model, specific heat capacity equal to 2000 j.kg-1.K-1 and thermal conductivity equal to 0.2 W/m.K and viscosity equal to 0.03499 kg/m.s.

The present model is designed in two dimensions using Design Modeler software. The model consists of a circular cross-section of a pipe with 4 rows of outer fins on the tube’s inner wall and 4 rows of inner fins on the outer wall of the tube.

The meshing has been done using ANSYS Meshing software, and the mesh type is structured. The element number is 17856.

Triplex Tube Methodology

Since the present work aims to investigate the changes in solid and liquid phases due to melting and freezing over time, the solidification and melting model has been used.

To define the solidification and melting model, the maximum temperature at which only the liquid phase prevails (T_solidus) is equal to 70 ℃.

The minimum temperature at which only the liquid phase is dominant (T_liquidus) is equal to 82 ℃, and the latent heat of solvent melting in the pure state (pure solvent melting heat) is equivalent to 176000 j/kg.

The inner wall of the tube, its outer fins, and the outer wall of the tube and its inner fins have a constant temperature equal to 90 ℃, While the phase change material inside the tube has an initial temperature of 27 ℃.

The simulation is unsteady because the present work aims to investigate the process of melting the phase change material inside the tube over time.

Triplex Tube Conclusion

At the end of the simulation process, the results of the present work are compared and validated with the results in the paper.

For this purpose, the diagrams in Figures 7 and 13 of the paper are used, which are related to changes in the average temperature of phase change materials over time and changes in the liquid mass fraction resulting from the melting process over time, respectively.

The present work is related to the state of the paper in which the phase change materials are simultaneously affected by the inner and outer fins. The following figures show the comparison of the results of the present CFD simulation with the results of the article.

Also, after the solution process, two-dimensional contours related to pressure and temperature and the liquid mass fraction resulting from the melting process are obtained. Because the simulation process is transient, the present work results are taken at different times of the simulation output.