PCM Battery Thermal Management: ANSYS CFD Tutorial

Lithium-ion batteries power modern electric vehicles and industrial grids. When these large energy arrays discharge electricity rapidly, they generate intense internal friction and heat. If this severe thermal energy stays trapped inside the cells, the entire pack can catch fire. Engineers call this catastrophic failure a thermal runaway. Traditional liquid cooling systems remove this danger efficiently, but they are incredibly heavy and require complex electrical pumps to function.

Guided by the thermal investigations of Zhang et al. (2025), our objective in this CFD project is to simulate a lightweight, passive alternative. We use ANSYS Fluent to observe how Phase Change Materials (PCM) control the lithium battery thermal condition organically. By understanding how a solid block melts to absorb dangerous heat, designers can build safer, passive cooling systems without relying on moving parts.

• Reference [1]: Zhang, Bixiao, et al. “Numerical investigation of lithium-ion battery thermal management system performance influenced by physical properties of PCM.” Journal of Energy Storage117 (2025): 116141.

Figure 1: The computational domain housing the cylindrical lithium-ion cells inside the phase change material.

Simulation Process: Solidification and Melting Phase Change Model

The virtual testing space contains 16 cylindrical lithium-ion cells. These hot components sit securely inside a solid Capric acid block measuring 92 mm wide and 65 mm tall. We apply a dense polyhedral mesh to capture the tight physical boundaries between the batteries and the cooling block. To track the physical transition from a solid into a liquid, we activate the Solidification and Melting physical model. This model utilizes the enthalpy-porosity formula to calculate how much thermal energy the material absorbs before its physical structure breaks down. We force the battery array to discharge power at a rapid 1C rate for a full duration of 3600 s. Learning the settings of battery module in ANSYS is a fundamental skill taught in our comprehensive battery and fuel cell CFD tutorials.

Figure 2: The high-quality polyhedral grid ensuring accurate thermal calculation across the solid boundaries.

Post-processing: Analysis of BTMS Thermal Physics

The thermal physics of a phase change cooling system demonstrate a brilliant natural defense against overheating. The safety process begins with sensible heating. The temperature history graph tracks the system starting at a safe baseline of 298 K. As the 1C electrical discharge begins, the cells heat up rapidly. For the first 900 s, the Capric acid remains completely solid. It simply absorbs the escaping thermal energy and gets hotter. However, a major physical shift occurs right at the 900 s mark. The temperature curve stops climbing sharply and flattens into a gentle slope. The Capric acid reaches its melting point and begins latent heat absorption. It swallows the incoming energy to destroy its own solid chemical bonds instead of raising the global temperature. Because the material sacrifices its solid state, the system finishes the 3600 s test at a highly controlled peak of 304.74 K.

The spatial contours illustrate the mechanics of this latent heat absorption. At 3600 s, the temperature distribution displays a maximum of 304.74 K located flatly on the cell tops. The surrounding Capric acid pulls this heavy thermal load away constantly. This creates a sharp gradient where the nearby material sits securely between 302.20 K and 302.83 K. The extreme outer walls of the block remain dark blue. This proves the core is thermally isolated from the outside environment.

Figure 3: The maximum temperature history tracking the vital shift from fast sensible heating to slow latent heat absorption.

We evaluate the liquid fraction history to measure the true capacity of the design. The physical melting begins near 900 s and climbs steadily to a peak value of 0.151. This proves the block is only 15 % melted by the end of the harsh cycle, holding a massive 85 % of its cooling potential in solid reserve. The spatial melting progression captures this physical transformation perfectly. Thin liquid films form directly around the hot cylindrical walls. As time passes, these isolated liquid rings expand outward and crash together in the center gaps. The outer corners remain fully solid blue. This continuous melting behavior proves the passive system successfully prevents thermal runaway by trapping the danger inside a controlled, internal liquid pool.

Figure 4: The final spatial temperature distribution confirming the cooling block pulls dangerous heat away from the cell walls.

Figure 5: The liquid fraction history proving the active thermal management system retains a massive cooling reserve.

Figure 6: The spatial melting progression showing liquid organizing at the cell walls and merging internally.

FAQ About PCM Battery Thermal Management

• How does Phase Change Material (PCM) control battery temperatures? Before the material melts, the heat simply makes the solid block hotter. Once it reaches its melting point, it uses all the incoming battery heat to change its physical state into liquid. It swallows the heat for this chemical change, which stabilizes the battery temperature instantly.

  How much of the Capric acid melted during the simulation? By the end of the 3600 s discharge cycle, the peak liquid fraction reached 0.151. This means only 15 % of the block melted, leaving a large portion of the solid available for further cooling.

• Why does the temperature stop rising quickly after a certain point? Before the material melts, the heat simply makes the solid block hotter. Once it reaches its exact melting point, it uses all the incoming battery heat to change its physical state into liquid. Because it swallows the heat for this chemical change, the temperature of the entire system stabilizes instantly.