Comprehensive parametric and design review for reducing pulsating heat pipes dependence on space orientation

It has been three decades since pulsating heat pipes were first introduced and garnered more attention due to their uncom-plicated structural design and superior heat transfer capabilities. The pulsating heat pipe of the original design is strongly affected by space orientation, which is connected with the influence of gravity. Even though more turns will hold pulsating heat pipe operational in any orientation, more space is needed to handle pulsating heat pipes, limiting its potential in space and the power electronics industry. This paper aims to present a comprehensive review of pulsating heat pipe's progress based on the most recent findings of both experimental and theoretical investigations of parametric influence on pulsating heat pipe thermal performance in horizontal and top heating modes. It aims to identify research gaps in pulsating heat pipe functioning in different orientations. Additionally, a comparative analysis of pulsating heat pipe design features described in the existing literature is conducted to determine the most promising designs for orientation-independent pulsating heat pipe systems. It is concluded that the integration of design attributes, encompassing an uneven-turn design, a channel struc-ture featuring alternating shapes and size of cross-section, and the utilization of nanofluids and binary mixtures as heat carriers are expected to serve as the basic reference for researchers aiming to achieve a stable pulsating heat pipe operation devoid of gravitational influences.