Thermal performance and flow characteristics in additive manufactured polycarbonate pulsating heat pipes with Novec 7000

To improve the performance of electronic devices, incorporating an effective cooling system in their thermal design is important. A pulsating heat pipe (PHP) is a passive cooling device that efficiently transports heat as sensible heat and latent heat from an evaporator section to condenser section via an oscillatory two-phase flow. In recent years, with the progress of additive manufacturing technology the design of PHPs with increased flexibility and wider industrial applicability has been expected. To optimize a plastic PHP flow channel structure for practical uses, the effects of channel geometry and flow regime on appropriate operating conditions need to be clarified at higher input power. The present study focuses on the flow visualization of a plastic-based PHP having a practical channel size and configuration. Using additive manufacturing, a serpentine flow channel of the PHP was fabricated with transparent polycarbonate. The PHP was filled with Novec 7000 as a working fluid, and the effects of the flow channel size and fill ratio of the working fluid on PHP's heat transport performance were investigated. Based on the flow visualization images, we evaluated the flow pattern and two-phase flow parameters such as vapor-slug lengths, velocity, and passing frequency, and clarified the relationship between the oscillating flow and thermal performance during the PHP operation.