Air Conditioning with PCM CFD Simulation

Air Conditioning with Phase Change Material CFD Simulation by ANSYS Fluent

The present problem simulates Air Conditioning with PCM using ANSYS Fluent software.

In general, phase change materials are materials with organic compounds that can absorb and store large amounts of latent thermal energy.

Thermal energy storage in these materials is achieved during the phase change process (solid phase to liquid or vice versa); So that when changing phase from solid to liquid, it absorbs heat from the room environment (causes cooling during hot hours) and returns the heat to the environment when changing phase from liquid to solid (causes heating during hours).

The present model is designed in two dimensions using Design Modeler software. The model includes a rectangular domain with dimensions of 0.09 m * 0.5 m. Four specific areas for defining phase change material are distinguished within this computational area.

The model meshing has been done using ANSYS Meshing software, and the mesh type is Structured. The element number is 45000.

Also, due to the nature of the present problem, a transient solver is enabled to perform the simulations.

Air Conditioning with PCM Methodology

The solidification and melting model is used in this simulation to define phase change materials. The phase change material studied in this simulation is rubidium-rt20 which has a density equal to 1480 kg/m3, a specific heat capacity equal to 2500 j.kgK, a thermal conductivity equal to 0.6 W/mK and viscosity equal to 0.164428 kg/ms.

To determine phase change materials, it should be noted that the maximum temperature at which the solid phase temperature is (solidus temperature) is 295.15 K, and the minimum temperature at which the liquid phase is dominant (liquidus temperature) is 297.15 K. And the pure solvent melting heat is defined as 150,000 j.kg-1.

The present model has a section for inlet flow in its upper part and a section for outlet flow in its lower part. Airflow with a flow rate of 0.018 kg.s-1 and a temperature of 302.15 K enters the model horizontally and exits at a pressure equal to atmospheric pressure.

The simulation was performed in transient format with a time step similar to 0.5 s. Moreover, the RNG k-epsilon model and energy equation are enabled to solve turbulent fluid equations and calculate temperature change within the domain, respectively.

PCM Conclusion

At the end of the solution process, two-dimensional contours related to the liquid’s pressure, velocity, temperature, and mass fraction are obtained.

Given that the phase change material’s working process is time-dependent, the transient solver is used, and the results are obtained at different times of the simulation process to get the results over time.

According to the temperature and mass fraction of the liquid, it can be said that the number of liquid production increases over time. The images also show that pressure and velocity stabilize over time and simultaneously have approximately the same values.