Thermal Impedance and Dynamics of Phase Change Materials under Pulse Train Heating

Phase change materials (PCMs) are excellent candidates for the thermal management of high-power pulsed electronic systems due to their high latent heat of fusion and ability to transform reversibly, but they are often limited by the rate at which they can absorb transient heat. By combining PCMs with high thermal conductivity matrices (e.g., copper foams of sufficiently small pore size), an effective composite slab with the favorable attributes of each component forms. While such composites are theoretically promising, the dynamics of the transient heat transfer process of such a PCM composite under high power pulses remains unclear and demands investigation. Numerical models have previously revealed an anti-resonance zone corresponding to a region of maximal buffering of the transient temperature rise, which depends on thermal conductivity, heat capacity, latent heat of fusion, and geometric factors, including the thickness of the slab. However, experimentally identifying frequencies at which a composite PCM layer buffers a temperature rise and the extent to which it does so remains challenging in materials with nonlinear thermal responses. Here, we develop a contact thermal characterization technique to investigate the dynamic response of a composite PCM slab that undergoes pulsed heating on one side and a quasi-constant temperature boundary condition on the other. We capture the depression in the temperature signal near a heated surface, representing the heat transfer surface of an electronic device or component. The outcomes of the experimental technique provide insights into the thermal impedance of the composite and the underlying thermophysical properties related to absorbing and transferring heat optimally.