Effects of Boundary Conditions on the Dynamic Response of a Phase Change Material

The dynamics of oscillatory melting-solidification fronts in finite thickness slabs are relevant for a variety of natural and engineered systems. In electronics packages, slabs of phase change materials (PCMs) are considered as a means of increasing the thermal capacitance and mitigate transient temperature rise within the package by melting and absorbing heat. In this context, the frequency-dependent dynamic response of a PCM reveals the rate at which it can effectively absorb and release heat and buffer a transient heat pulse. This study presents a numerical investigation of the transient thermal response of a slab to a harmonic heat flux boundary condition on one side and a constant temperature or convective cooling boundary condition on the opposite side. Within this particular regime, the internal temperature profile is strongly perturbed from the single-phase case due to heat being absorbed (released) during melting (solidification) at the solid-liquid interface. This results in a phase lag ∆ϕ and a depression in the peak temperature ∆T at the heat source. The magnitude and frequency dependence of this anti-resonance depends on the characteristics of the periodic heating function, material thermophysical properties, the thickness of the slab, and the nature of the applied cooling boundary condition.