A Comprehensive Review of Thermal Performance Improvement of High-Temperature Heat Pipes

Energy efficiency issues are being focused on the growing concern of global warming and environmental pollution. The high-temperature heat pipe (HTHP) is an effective and environmental-friendly heat transfer device employed in many industries, including solar power generation, high-temperature flue gas waste heat recovery, industrial furnaces, nuclear industries, and aviation. As a critical factor in HTHPs, thermal performance is mainly introduced in the entire paper. To date, most reviews have been published concerning one or several application scenarios. However, to the best of authors’ knowledge, it is hard to find a review discussing how to improve the thermal performance of HTHPs comprehensively. First, the impact on the performance of three main components of HTHPs over the past 30 years is introduced: the working fluid, the HTHP structure, and the wick structure. Herein, it is a considerable review of the optimal operating conditions for each direction, and we expect this paper contribute to improving the thermal performance of HTHPs. Then, current numerical simulations and theoretical research on the heat transfer limit of HTHPs are recommended. The significant hypotheses used in numerical simulations and the present theoretical studies are compiled here. Finally, some potential future directions and tentative suggestions for HTHP research are put forward.