Journal of Thermal Science and Technology (Jun 2019)
Evaluation on cooling performance and reliability of low-height aluminum thermosyphon in high-temperature environment
Abstract
Information and communication technology (ICT) cooling devices increasingly need to be able to be installed in high-density packaged equipments, especially these exposed to high-temperature environments such as 1U-height servers and packet transport systems (PTS) for telecommunication networks. Therefore, in this study, we have developed a low-height and cost-effective aluminum thermosyphon with a boiling surface that has a porous structure by using a micro-curl skived fin and fluorine-based refrigerant (HFE7000) usable at over 50°C. This research aimed to evaluate the cooling performance and reliability of this aluminum thermosyphon when exposed to temperatures over 50°C and to determine an operating limit temperature. Thus, we carried out cooling performance tests of our thermosyphon supplied with hot air up to 100°C and high-temperature aging tests to examine its corrosiveness in an environment containing aluminum and HFE7000. From these examinations, we concluded the following. (1) The cooling performance at a heat input of 100 W was quite stable with the intake air up to 100°C without an excessive temperature rise of the boiling surface. (2) Until the intake air was up to 60°C, in which the plastic deformation of the boiling part did not occur, the thermal resistance of the boiling surface decreased as the increase of the saturated vapor pressure, and the minimum wall superheat of the boiling surface was 1.6 K and the maximum boiling-heat-transfer coefficient was 57 kW/(m2K). (3) The generation rate of fluorine ions increased as the temperature rose due to the promotion of the hydrolysis reaction between HFE7000 and dissolved water. (4) Under an actual use condition of the thermosyphon, fluorine ions due to the hydrolysis reaction of HFE7000 were barely generated, and aluminum corrosion due to fluorine adsorbed on the aluminum surface barely occurred either. (5) The operating limit temperature of this aluminum thermosyphon was 60°C from strength constraints.
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