Performance characteristics of flat-plate oscillating heat pipe with porous metal-foam wicks

In this study, a flat-plate oscillating heat pipe (FPOHP) with its channel bottom covered by sintered copper-foam wicks was fabricated. The overall size of FPOHP is 150 mm x 100 mm x 7.5 mm, having rectangular cross-section channels with a hydraulic diameter of about 1.64 mm. The start-up and heat transfer performance of the porous-based FPOHP were experimentally investigated and compared with a conventional smooth-channel FPOHP at the vertical orientation. Ethanol was used as the working fluid at a volumetric filling ratio of about 50%. Experimental results showed that the copper-foam wicks enabled a profound improvement in the FPOHP performance and reduced the start-up temperature and time duration significantly. Compared with the conventional FPOHP, temperature fluctuations with smaller amplitudes and better temperature uniformity were observed for the porous-based FPOHP. However, local dry-out appeared earlier in the porous-based FPOHP when the power input was greater than about 207 W because the robust nucleation boiling induced vapor layer covered the wicks, preventing the backflow of liquid to the evaporator and causing the heat transport limitation. To extend the applicable possibility of porous-based FPOHPs in thermal management of high energy utilization systems, the re-design and re-fabrication of copper-foam wicking structures are required. (C) 2019 Elsevier Ltd. All rights reserved.