Heat transfer coefficient effect on thermal impedance of phase change composites

Le résumé fourni par la source

Thermal management for high power electronics prioritizes minimizing thermal resistances between the heat source and the ultimate heat sink. This often sacrifices thermal capacitance, resulting in overheating under transient thermal loads. Phase change composites (PCCs) composed of conductive scaffolds infiltrated with phase change materials when added in series between a heat source and a heat sink increase the effective thermal capacitance at the cost of increased thermal resistance. The impact on thermal impedance ( Z th ) depends on both the heat-pulse period and the heat sink’s effective heat transfer coefficient ( h eff ). In this study, Z th of a PCC slab was measured experimentally under isolated square-wave heat pulses of 4.25 W cm -2 and on-times between 0.01–2000 s. The h eff was tuned from 500 to 5000 W m -2 K -1 (approximately representing natural convection of water to forced convection in water) by using layers of insulation between the PCC and a cold plate. As h eff decreases, the magnitude of Z th suppression due to melting effects increased in magnitude and range of on-times. Importantly, the h eff was observed to dictate the pulse length over which a PCC decreased the thermal impedance relative to a solid copper block under equal volume basis. PCCs decrease junction temperatures while simultaneously reducing size and weight of systems under conditions where (1) the input power is short relative to steady-state conditions and (2) high h eff are not available due to engineering constraints.

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