Thermal Management by PCM in a Room Wall

Thermal Management by PCM in a Room Wall, CFD Simulation ANSYS Fluent Tutorial

Description

A Phase Change Material (PCM) releases or absorbs substantial energy as it melts and solidifies at a specific temperature, making it well-suited for temperature control applications — absorbing significant heat during melting and releasing that stored heat back during solidification. PCMs find use across a range of applications requiring stable temperatures and energy storage, including heating pads, cooling systems for telephone switching boxes, and thermally responsive fabrics used in bedding and clothing.

This project models a square-shaped room whose wall consists of three material layers: brick, Trimethylolethane/water (the PCM layer), and concrete, arranged from outer to inner surface. The brick's outer surface is exposed to a heat flux of 100 W/m², with all three wall materials sharing low thermal conductivity — a combination intended to help the room resist rapid thermal fluctuations.

The 3D geometry represents a 3 m square domain plus the three wall layers, each 10 cm thick, built in Design Modeler. The domain was meshed in ANSYS Meshing using a structured grid totaling 193,500 elements.

Methodology

The Solidification and Melting model was used to simulate the PCM's thermal loading behavior. A pressure-based solver was employed given the fluid's incompressibility, and since the process depends inherently on time, the simulation was run as transient, with gravitational effects excluded.

Conclusion

Results include 2D contours and vector fields of pressure, temperature, turbulence kinetic energy, and velocity. The results show that reaching a PCM volume fraction of 1 — meaning the Trimethylolethane/water layer melts completely — takes approximately 6 days, illustrating how long this material takes to fully store the energy it absorbs from incoming radiation.

The room's interior temperature rises only very gradually throughout this process, a direct result of the low thermal conductivity shared by all three wall components (brick, PCM, and concrete). This behavior confirms the PCM's effectiveness at storing thermal energy for later use, supporting reduced energy and power consumption by smoothing out and delaying the transfer of heat into the living space.