Improving the performance of flat heat pipes by exploiting benefits of additive manufacturing

Next to the industrial pick-up of Flat Heat Pipe (FHP) technology, the overall understanding of its two-phase heat transfer characteristics will contribute to further improvements of its performance. In this study, an FHP with dimensions of 20x40x6 mm(3) was designed and manufactured. Investigations until now have concentrated on conventional manufacturing technologies rather than on the performance of FHPs using novel Additive Manufacturing (AM) techniques. Surface-functional wick structures were additively fabricated having the appearance of a screen mesh enriched with sintered-like microstructures. The effects of heat load (ranging from 7.5 to 82.5 kW/m(2)), cooling water temperature (ranging from 25 degrees C to 45 degrees C) and inclination angle (horizontal to vertical) on the FHP's heat transfer characteristics were examined experimentally. In this paper, key performance indicators, such as temperature distribution, thermal resistance and superheat, are discussed. Results show that the developed FHP can effectively transfer heat. Moreover, optimal combinations of cooling water temperature and inclination angle were found defined by the lowest superheat and thermal resistance. A minimum total thermal resistance of 0.30 K/W for a heat load of 67.5 kW/m(2) was reached for the following conditions: a) 30 degrees inclination angle and 25 degrees C cooling water temperature, or (b) horizontal orientation and 35 degrees C cooling water temperature. Moreover, as the cooling water temperature decreases from 45 degrees C to 25 degrees C, the condenser wall temperature decreases; however, thermal resistances do not decrease continuously as well. Also, tilting the FHP at relatively high heat loads does not impact the thermal performance. The FHP proposed in this study profits from novel AM fabrication capabilities and could suit thermal management challenges of current and future electronic components due to its excellent heat transfer characteristics, consistent temperature distribution and manufacturing flexibility.