Abstract
PHPs (pulsating heat pipes) using water are typically made of Cu and Si. Although Al is more sustainable than Cu and cheaper than Si (in addition to weight and durability advantages), water–Al PHPs have not been extensively investigated because noncondensable H2 gas is generated during Al–water reactions at high temperatures, stopping the flow in PHPs and degrading the thermal performance. In this study, a nontoxic micro-nano surface treatment method that is cheaper and simpler than the only reported method for water–Al PHPs was applied to the internal surface of an Al PHP. This prevented H2 gas production by forming Al(OH)3, thereby eliminating possible reaction sites on the surface. The internal two-phase flows, which significantly affected the thermal performance of PHPs, were compared using a flow visualization technique. The dry-out region gradually expanded in the original PHP with increasing operation time. In contrast, the modified surface PHP exhibited flow regeneration, preventing dry-out, as well as a thermal resistance 45.8% lower than that of the original surface PHP. Further, the critical heat flux of the PHP remained at 4.57 W/cm2 with the modified surface. Therefore, the proposed method improved the performance and durability of water–Al PHPs.
Published Version
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