Directly air-cooled compact looped heat pipe module for high power servers with extremely low power usage effectiveness.

• New performance enhancement mechanism for looped heat pipe operation is proposed. • Different looped heat pipe prototypes were developed for comparison. • An air-cooled looped heat pipe with 550 W capability at horizontal position was achieved. • The nominal power usage effectiveness of the LHP module is very low. • The novel looped heat pipe module was implemented into server onboard cooling test. The rapid development of data centers has brought huge energy consumption around the world, and an effective, reliable and energy-saving cooling method is urgently demanded for data centers cooling. This paper proposed air directly cooling looped heat pipe (LHP) modules with excellent thermal performance that can be used for server cooling in data centers based on the unconventional enhancement mechanism for looped heat pipes. The proposed LHP with no compensation chamber has an auxiliary wick which connects the primary wick in the evaporator and extends into the condenser to promote the liquid replenishing. Meanwhile, another approach for reducing the sensible heat leak in the replenishing liquid was introduced with aid of an additional fin and fan assembly installed very close to the evaporator entrance. By means of the above approaches, significant improvement in maximum sustainable heat load of the LHP in horizontal direction was achieved. The improved LHP module has a maximum heat dissipation capacity of 550 W with the minimum total thermal resistance of 0.16 °C/W in horizontal direction, and with a power usage effectiveness as low as 1.02. [ABSTRACT FROM AUTHOR]