Passive thermal management strategies for high-ambient-temperature environments: A comparative study of heat sinks integrated with pulsating heat pipes and vapor chambers

초록

The ongoing drive toward high-power yet miniaturized military electronics requires robust passive thermal management relying on natural convection, as strict form factors, noise, vibration, and power constraints preclude active cooling solutions. However, conventional passive heat sinks often fall short in dissipating high heat fluxes due to their limited thermal spreading capabilities. To address these challenges, we develop and experimentally evaluate two phase-change heat sink designs, one integrated with a pulsating heat pipe (PHP) and the other with a vapor chamber (VC), to enhance cooling performance in high-ambient-temperature environments. Thermal performance was evaluated at an ambient temperature of 50 degrees C, aligning with the 49 degrees C requirement of the U.S. military standard MIL-STD-810H (Method 501.7, High Temperature), under a 32 W heat load simulating a graphics processing unit. A geometrically identical solid aluminum control heat sink maintained the temperature below the 90 degrees C operational limit at 25 degrees C, yet failed to meet the requirements at 50 degrees C, reaching a maximum of 99.2 degrees C. For the phase-change heat sinks using SF33 as the working fluid, a 50 % filling ratio was identified as optimal for both the PHP and VC designs. The optimized PHP heat sink reduced the maximum heater temperature to 90.8 degrees C, marginally exceeding the operational limit. In contrast, the optimized VC heat sink successfully lowered the maximum temperature to 87.4 degrees C, satisfying the operational criterion. This VC design achieved a temperature reduction of 11.8 degrees C and a decrease in total thermal resistance of 24.2 % relative to those of the aluminum control. These results demonstrate that the VC-integrated heat sink is a highly viable solution for the passive cooling of high-power military electronics operating in high-ambient-temperature environments via natural convection.

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