Thermal performance and mechanism of PCM-integrated cross-flow microchannel cold plates

Abstract

Efficient thermal management of high heat flux energy storage systems remains challenging because maintaining temperature uniformity under transient thermal loads is difficult. To address this issue, a phase-change-material (PCM)-integrated cross-flow microchannel cold plate is proposed that combines active liquid cooling with passive thermal energy storage to achieve synergistic thermal management. An experimentally validated three-dimensional numerical model is employed to systematically investigate the effects of PCM type (RT31, RT35, and RT42), PCM thickness (3 and 5 mm), and heat generation power (3–4 kW) on the thermal and hydraulic performance of the proposed system. Results show that PCM integration reduces the heat-source surface temperature by 3–5 °C and significantly enhances thermal uniformity. Among the tested PCMs, RT31 exhibits optimal performance because its melting temperature closely matches the operating conditions. While PCM thickness has a limited impact on steady-state temperature, it affects the transient thermal response. The introduction of PCM alters the thermal boundary condition from constant-heat-flux to near-isothermal conditions, reducing the wall-to-fluid temperature difference and leading to an apparent increase in the effective convective heat transfer coefficient of up to 132%. This increase primarily arises from the modified thermal boundary condition and the resulting reduction in temperature driving force, although a genuine contribution from enhanced fluid-side convection is also observed. Based on full-factorial experimental data, a generalized Nusselt number (Nu) correlation was developed by incorporating the Stefan number and PCM thickness ratio. The proposed correlation achieves an R2 value of 0.971 and shows a maximum deviation of 8.2% when compared with literature data. The proposed model provides a predictive framework for evaluating heat transfer performance in PCM-integrated cooling systems and offers insights into underlying heat transfer mechanisms.