Diffusion-bonded pulsating heat pipes: fabrication study and new channel proposal

Abstract

In the present work, diffusion bonding technology used for fabrication of pulsating heat pipes (PHP) in a high-vacuum, high-pressure and high-temperature furnace is discussed. Seven different configurations of PHPs were manufactured, subjected to different fabrication parameters. PHPs with 10 and 26 parallel channels of circular and square cross-sectional areas were constructed. In addition, a PHP with a novel cross-sectional channel geometry, composed by a circular area with lateral grooves, which is easily fabricated by the present technology, is proposed. The deformation of the geometries of the channel cross sections was observed. The square channel PHP showed large deformation, while the deformations of the circular ones, including the new proposed geometry, were small. The distribution of the PHPs along the matrix in a single bonding cycle showed to be a very important parameter: Those PHPs produced in parallel presented some deformation and leakage problems, while those made by stacking mode did not presented any leakage. Scanning electron microscopy and optical microscopy were used to assess that diffusion bonding is a very suitable and promising technology for the fabrication of PHPs. The thermal tests showed that the grooved circular channel PHP presents higher thermal performance.