Phase Change Material (PCM) for Thermal Management of Lithium-Ion Battery Pack

Phase Change Material for Thermal Management in Lithium Battery Packs

Introduction to the Session

• The session focuses on using phase change materials (PCM) for thermal management in lithium battery packs, specifically analyzing a single cell.

• Objectives include preparing geometry, generating mesh, selecting names for computational domains, applying boundary conditions, and visualizing results.

Geometry Preparation

• The analysis will utilize ANSYS Design Modeler to prepare the geometry of a single lithium-ion cell with PCM.

• Initial steps involve setting units to millimeters and creating two cylinders representing PCM and the lithium-ion cell.

• The first cylinder is designated as PCM with a radius of 17 mm; the second cylinder represents the cell with a radius of 9 mm.

Mesh Generation

• After defining geometries, users are guided to generate default mesh and assess its quality based on node count.

• Aiming for better mesh quality, an element size of 0.01 is chosen resulting in approximately 1 million nodes.

Name Selection and Updates

• Name selections are created for both PCM and cell boundaries to facilitate further analysis.

• Upon updating the mesh translation to Fluent successfully, users can proceed by closing the meshing tool.

Setup Configuration

• Users are instructed to open setup windows where they can configure transient settings including gravity effects.

• Energy equations are activated; solidification and melting processes are defined due to PCM usage.

Material Properties Specification

• New material properties for n-octadecane (PCM), including density (721 kg/m³), specific heat (2180 J/kg·K), thermal conductivity (0.15 W/m·K), viscosity (0.035 Pa·s), melting heat (119000 J/kg), solidus temperature (303 K), and liquidus temperature (305 K).

Solid Materials Definition

• Nickel is specified as a solid material alongside aluminum; these materials must be correctly assigned within zone conditions.

Boundary Conditions Application

• Boundary conditions set at approximately 307 K for both cell boundary contact regions using nickel material properties ensure accurate simulation results.

Solidification and Melting Visualization in PCM

Area Averaged Average and Temperature Settings

• The discussion begins with the area averaged average focusing on solidification and melting processes, particularly visualizing liquid fractions in Phase Change Materials (PCM).

• Instructions are provided to initialize the settings for visualization, including creating output parameters and accessing animation options.

Solution Animation Setup

• A new contour object is selected to visualize solidification, melting, and liquid fraction using a float color map for better scaling.

• The total temperature is also set up for visualization, ensuring that a float scale is applied for clarity.

Running Calculations

• The calculations are prepared to run with autosave features enabled. Time steps are set to 100 with a size of one second each.

• Observations begin regarding the liquid volume fraction variations during the heating process, indicating how temperature changes affect PCM.

Visualizing Results

• As calculations progress, variations in temperature along the PCM are noted alongside changes in liquid fraction due to heating.

• The increase in liquid fraction correlates with rising temperatures as solid materials undergo melting.

Monitoring Changes Over Time

• Continuous monitoring reveals that as time progresses (up to 50 seconds), both temperature and liquid volume fractions increase significantly.

• By running simulations longer (500–600 seconds), more detailed observations of volume fractions can be captured effectively.

Final Observations After Initial Steps

• At the end of 100 time steps, significant increases in both liquid fraction (0.027) and total temperature (~303°C) are recorded.

• Further iterations show that after 400 seconds of flow time, the liquid volume fraction reaches approximately 0.35 while temperatures exceed 305.5°C.

Conclusion on Simulation Progression

• It’s emphasized that additional time steps will enhance visualization accuracy; thus further runs are planned for comprehensive analysis.

PCM Liquid Volume Fraction Analysis

Overview of Liquid and Solid Fractions

• The presentation discusses the liquid volume fraction in relation to phase change materials (PCM), highlighting how different colors represent solid (blue) and liquid (red) fractions.

• The calculations for the liquid fraction and total temperature have been completed, indicating a clear distinction between solid and liquid states within the PCM.

Flow Time Progression

• As the simulation progresses, it notes that the flow time is approximately 400 seconds, with plans to extend this duration by an additional 100 seconds to observe changes.

• After running for another 100 seconds, the volume fraction reaches around 457, suggesting significant changes in state as time progresses.

Temperature Control Observations

• At a flow time nearing 500 seconds, variations in temperature are observed; specifically, temperatures exceed 305 degrees Celsius while monitoring liquid fractions. This indicates active heat transfer through the PCM.

• The color contour changes signify increased heat movement within the material, reflecting dynamic thermal behavior as conditions evolve over time.

Continued Monitoring of Liquid Fraction

• By around 600 seconds into the simulation, further increases in liquid fraction are noted—slightly above 0.8—and temperatures remain just below or slightly above 306 degrees Celsius. This suggests ongoing phase transitions within the PCM system.