Topology optimization of dual-phase-change material heat sinks for minimizing temperature oscillations

Abstract

This study presents a topology optimization framework for dual-phase-change material (dual-PCM) heat sinks under time-varying thermal loads, with temperature oscillation suppression as the primary objective. The framework is developed based on the FEniTop platform and extended to transient nonlinear heat conduction with phase change. A degraded discrete material optimization (DMO) interpolation scheme is adopted to handle the distribution of a high-conductivity material (HCM), a low-melting-point alloy (LMPA), and a conventional PCM in a unified manner while ensuring clear material separation. The method is first applied to two-dimensional benchmark problems to quantify the benefit of introducing LMPA. Compared with the HCM-PCM configuration, the addition of 10% LMPA yields an additional 11.2% reduction in the objective function, indicating that LMPA provides an extra degree of control over the transient thermal response beyond conventional single-PCM buffering. The framework is then extended to three-dimensional heat sink design under oscillatory heat fluxes with different loading levels and LMPA fractions. The results show that the optimal role of LMPA is strongly load dependent. At low heat flux, the thermal response remains largely conduction-dominated, phase-change participation is limited, and increasing LMPA exhibits diminishing returns. At intermediate heat flux, the system enters a coupled regime where local source-side buffering and global heat redistribution coexist, allowing additional LMPA to continuously improve oscillation suppression. At high heat flux, phase-change participation becomes nearly fully activated, and the optimized design favors enhanced primary heat transport pathways that couple heat conduction with distributed latent heat absorption, again without diminishing returns. These results demonstrate that dual-PCM topology optimization provides an effective approach for transient passive thermal management under non-steady thermal loads. More importantly, the study reveals how multiple phase-change materials should be spatially arranged to coordinate conductive transport, latent heat storage, and thermal buffering for suppressing temperature oscillations.