Experimental investigation of a coil shaped deployable pulsating heat pipe

The development of foldable heat transfer devices is currently a quite intriguing technological challenge in the field of thermal management. Due to its simple structure (i.e. capillary tube without any wick structure inside), the Pulsating Heat Pipe is one of the most promising candidate to be applied to foldable devices. A possible solution is to realize a PHP with the adiabatic section formed as a coil. In this case the adiabatic section is very long and the performance of the PHP can be largely affected. This paper presents the results of the comparison between two twin PHPs built with the same geometry but different adiabatic section shapes (planar and coil). A full thermal characterization of the planar assessment for different working fluids has been performed: HFE-7000 (filling ratio: 70%) shows the best thermal behavior in horizontal orientation. On the other hand, the coiled PHP has been tested under different orientations and folding configurations (different mutual locations of the evaporator and condenser with respect to gravity) and compared with the planar reference case. The coiled PHP in some configurations seems to present worse thermal performances than the planar one.