Development of cryogenic loop heat pipes: A review and comparative analysis

• A comprehensive review of development of cryogenic loop heat pipes is presented.
• Comparative analysis between ambient and cryogenic loop heat pipes is conducted.
• Cryogenic loop heat pipes are categorized based on their structure characters.
• More attention is paid to the supercritical startup of cryogenic loop heat pipes.
• A variety of factors affecting cryogenic loop heat pipe performance are analyzed.

Loop heat pipes (LHPs) are highly efficient two-phase heat transfer devices with the ability to transport a large amount of heat over a long distance. Due to increasing demand of efficient cryocooling applications in both space and terrestrial surroundings, LHPs operating in cryogenic temperature range have been extensively investigated in recent years. This work provided a comprehensive review of the state-of-the-art of cryogenic loop heat pipes (CLHPs). Five different types of CLHPs were categorized, and a comparative analysis between CLHPs and ambient LHPs and among different types of CLHPs was conducted. More attention was paid to the supercritical startup of CLHPs, and the operation and performance characteristics of different types of CLHPs were compared in terms of system structure, supercritical startup, heat transport capacity and the effect of parasitic heat load. The parameters that affect the CLHP performance were analyzed, and the optimization strategy was proposed in order to progress their future development and engineering applications.