Thermal performance optimization of nanoparticle-enhanced PCMs in a wavy trapezoidal cavity: a computational study

Reducing the duration of the total melting process is a key challenge in thermal energy storage (TES) systems. This study numerically investigates the enhancement of TES thermal performance using a trapezoidal prism storage unit filled with nano-enhanced phase change material (NEPCM). The bottom wall (wave wall) is heated while the remaining walls are insulated, and its shape is modified while keeping the PCM volume constant. The study evaluates four TES configurations with different bottom wall geometries: Case 1 (sawtooth waves), Case 2 (triangular waves), Case 3 (sinusoidal waves), and Case 4 (square waves). The phase transition is modeled using the enthalpy-porosity method. The effects of bottom wall temperature (333 K and 343 K) and nanoparticle concentration (φ = 0–0.04) are also analyzed. The analysis examines temperature distributions and liquid fraction evolution across the four configurations under two different temperatures. The findings revealed that incorporating nanoparticles at a concentration of 4 vol% enhanced thermal conductivity during the melting process by 9.2 %. Increasing the bottom wall temperature to 343 K accelerated the melting process by 75 %. Among the tested designs, the TES system with a square-wave bottom wall (Case 4) achieves the highest efficiency, reducing melting time by 18 % compared to the sinusoidal-wave configuration (Case 3).