A pulsating heat pipe (PHP) was fabricated by a 3-D printer, and its heat transfer characteristics were investigated by experiments. A graphene-laden PLA (PolyLactic Acid) filament was used as a 3-D printing material. Ten square channels having a cross section of 1.5 mm × 1.5 mm and a length of 80 mm were made inside the PHP and the ends of channels were connected. Since the graphene-laden PLA filament allows electric currents to pass through, the 3-D printed PHP was electroplated by copper to maintain its airtightness. Ethanol was used as the working fluid. The filling ratio of the working fluid was 50 %. In experiments, an evaporator section of the PHP was heated by a heater and a condenser section was cooled using a water-cooling jacket. The heater power was changed from 2.0 W to 8.0 W while the cooling water temperature and its flow rate were kept at 4.0 °C and 0.25 LPM, respectively. The transient temperature distribution of the PHP was measured by thermocouples. Moreover, because the graphene-laden PLA is nontransparent, an X-ray imaging system was also employed to observe the two-phase flow phenomena occurring in channels of the PHP. From the experimental results, the continuous heat transport from the evaporator to the condenser section of the PHP was confirmed with vapor-liquid two-phase flow characteristics observed inside the channels.

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