PCM Shell and Tube Heat Exchanger: Paper Validation

Shell and Tube Heat Exchanger, PCM Thermal Storage System, Paper Numerical Validation, CFD Simulation by ANSYS Fluent

Description

This project simulates the solidification and melting of a phase change material (PCM) within a shell and tube heat exchanger, based on the reference article "Experimental and computational evolution of a shell and tube heat exchanger as a PCM thermal storage system," with results compared and validated against both the experimental and numerical results reported in the paper.

Phase change materials are organic compounds capable of absorbing and storing large amounts of latent thermal energy. This energy storage occurs during the phase transition itself: as the material melts from solid to liquid, it absorbs heat from its surroundings (producing a cooling effect), while as it solidifies from liquid back to solid, it releases that stored heat back into the environment (producing a heating effect).

The PCM used in this simulation is RT50-type paraffin, defined with a density of 820 kg/m³, specific heat capacity of 2000 J/kg·K, and thermal conductivity of 0.2 W/m·K. Its viscosity was defined as temperature-dependent, implemented through a UDF using an exponential function of temperature.

The heat exchanger itself is constructed from copper, with water flowing through the inner tube at a mass flow rate of 0.008318 kg/s and a temperature of 343.15 K, while the surrounding shell section is filled with the PCM.

Geometry & Mesh

The 3D geometry was designed in Design Modeler, representing a shell and tube heat exchanger with an inner tube wall thickness of 0.0025 m. The pipe spans 1 m in length, with inner and outer radii of 0.011 m and 0.0425 m, respectively. Given the pipe's symmetrical structure, only half the geometry was modeled to reduce computational cost.

The domain was meshed in ANSYS Meshing using a structured grid totaling 169,171 elements.

Methodology

The Solidification and Melting model was used to capture the PCM's phase-change behavior, defined with a solidus temperature of 317.2 K, a liquidus temperature of 327.3 K, and a latent heat of fusion of 170,320 J/kg.

Conclusion

A graph tracking the temperature evolution of the PCM-filled shell section over the course of a complete melting cycle was extracted and compared directly against Figure 8 of the reference article, which includes both experimental measurements and numerical CFD results. This comparison confirmed that the current simulation achieves acceptable accuracy relative to both the numerical and experimental results reported in the paper.

Additional 2D and 3D contours of pressure, temperature, and liquid mass fraction were also obtained, providing a detailed view of how the PCM transitions from solid to liquid throughout the shell as it absorbs heat from the circulating hot water in the inner tube.