Experimental study on the thermal performance of a liquid-cooled heat sink integrating heat pipes for dual CPU servers

Abstract

The increasing power consumption of server CPUs poses a challenge for data center cooling. In this work, a liquid-cooled heat pipe heat sink (LHPHS) with compactly arranged heat pipes is designed and fabricated for CPU cooling in dual CPU servers. Water is selected as the working fluid in the heat pipes. Experiments are conducted to explore the heat dissipation potential of LHPHS under high inlet coolant temperature and high heat load conditions, and to investigate the operational stability of LHPHS under the conditions of uneven heat generation between two CPUs. Furthermore, a one-dimensional thermal resistance network and numerical model of the LHPHS are established to quantitatively analyze the thermal resistance distribution of LHPHS and the variation of thermal resistance with coolant flow rate. The results show that, firstly, the LHPHS operates stably under high inlet coolant temperature and high heat load conditions, meeting the heat dissipation requirements of up to 37.5 W/cm2 with a coolant flow rate of 1 L/min and inlet coolant temperature of 35℃. Secondly, the LHPHS exhibits excellent performance in controlling temperature difference between CPUs and even when there is discrepant heat generation between them. Thirdly, the LHPHS performs a low thermal resistance, measuring 0.044 ℃/W at a coolant flow rate of 0.5 L/min, and this resistance further decreases as the flow rate increases. Additionally, it is observed that the thermal resistance of the liquid-cooled plate decreases with the increasing flow rate, and heat transfer within the heat pipes becomes a critical aspect under high coolant flow rates. Therefore, reducing the thermal resistance of the heat pipe is crucial for the thermal performance improvement of the LHPHS.