Mini-scale pulsating heat pipe cooling systems for high-heat-flux electronic equipment

Abstract

This paper presents a novel passive two-phase cooling system for efficient thermal management of high-heat-flux electronic equipment, namely a mini-scale, flat-plate pulsating heat pipe, by executing experiments on a test bench. Furthermore, cooling tests on an actual 1-U server are also shown. The pulsating heat pipe used in this study is designed and manufactured with micro-channel technology where passive two-phase flow circulation is promoted by the inherent two-phase instability and the competing effect between nucleate boiling and thin-film evaporation. Pulsating heat pipes properly operate with gravity (in vertical orientations) and without gravity (in horizontal orientations) and they are an optimal solution to dissipate a large amount of heat without the need of active drivers (absence of pumping power). The cooling capabilities of the proposed pulsating heat pipe were investigated using different near zero global warming potential refrigerants at various filling ratios to find the optimal thermal performance up to 800 W (corresponding to a heat flux of 25 W/cm2). The minimum overall thermal resistance was measured to be 0.065 K/W, which includes the thermal interface material and the secondary side. This paper shows that passive two-phase cooling using pulsating heat pipes can be a very promising and reliable technology for achieving high power dissipations of next-generation datacentres (and electronic equipment in general).