A composite phase change material thermal buffer based on porous metal foam and low-melting-temperature metal alloy

Abstract

Composite phase change materials consisting of a high-latent-heat phase change material (PCM) embedded in a high-thermal-conductivity matrix are desirable for thermally buffering pulsed heat loads via rapid absorption and release of thermal energy at a constant temperature. This paper reports a composite PCM thermal buffer consisting of a Field&apos;s metal PCM having high volumetric latent heat (315MJ/m(3)) embedded in a copper (Cu) matrix having high intrinsic thermal conductivity [384W/(m<bold>K</bold>)]. We demonstrate thermal buffer samples fabricated with Cu volume fractions from 0.05 to 0.2 and sample thicknesses ranging between 1mm and 4mm. Experiments coupled with finite element method simulations were used to determine the figures of merit (FOMs), cooling capacity eta(eff), energy density E-eff, effective thermal conductivity k(eff), and the buffering time constant tau. The cooling capacity was measured to be as high as eta(eff)=72 +/- 4kJ/(m(2)K(1/2)s(1/2)) for the 1.45mm thick thermal buffer sample having a Cu volume fraction of 0.13, significantly higher than theoretical values for aluminum-paraffin composites [45kJ/(m(2)K(1/2)s(1/2))] or pure paraffin wax [8kJ/(m(2)K(1/2)s(1/2))]. Our work develops design guidelines for high-FOM thermal buffer devices for pulsed heat load thermal management. Published under license by AIP Publishing.