Experimental study on thermal performances of flat-plate pulsating heat pipes under static and swing conditions

Abstract

Pulsating heat pipe (PHP), as an efficient heat transfer component, can be used for waste heat recovery and electronic cooling. The influences of typical ocean motions, such as inclination and swing, on thermal performances of PHPs are inevitable for practical offshore applications. In this study, surfactant-free functionalized multi-walled carbon nanotubes (f-MWCNTs) nanofluids with long-term stability were prepared. Thermal performances of PHP with f-MWCNTs nanofluids and mixed fluids under static and swing conditions were comparatively investigated. Results indicate that 0.25 mg/ml f-MWCNTs nanofluids (base fluid, 1:1 ethanol-DI water) shows the lowest thermal resistance among all working fluids. Thermal performances of flat-plate PHP with ethanol-DI water mixed fluids are better than that of ethanol-based f-MWCNTs nanofluids, and HFE-7100-DI water mixed fluids are more suitable for performance enhancements at the lower heat loads. As for effects of swing motion, the increased swing amplitudes and decreased swing periods will reduce thermal performances. In the worst case, swing motions can reduce thermal performances by 5.85%. Moreover, frequencies of temperature difference fluctuations increase with the decrease of swing periods. Although the change of swing amplitudes has a certain effect on frequencies and amplitudes of temperature difference fluctuations, but the influence seems negligible as well. These results can be used to guide practical offshore applications of PHPs.