# Simulation Study on Nanofluid Heat Transfer in Immersion Liquid-Cooled Server
## 1 Introduction  
With the rapid development of the Chinese digital economy and the continuous advancement of the informationization process, data centers have become an essential \"computing base\" to support the digital transformation of the economy and society, and are an important engine to fuel the vigorous development of the digital economy. High-throughput computing business makes the heat dissipation of server chips a serious challenge, with chip thermal package shell temperatures increasing, even reaching the limit of air-cooled heat dissipation. The specific heat capacity of liquid is 1000-3500 times that of air, and its thermal conductivity is 15-25 times that of air, so for higher-thermal-density heat dissipation, liquid cooling with greater heat capacity and faster heat transfer becomes the obvious choice. Among them, the single-phase submerged liquid cooling method is favored because of its high heat dissipation capacity and its advantages of safety and energy savings. Single-phase submerged liquid cooling immerses the electronic components of the server in a liquid-cooled cabinet, which is filled with a special cooling medium, and the heat is transferred out through the circulating flow of the coolant [1]. In 1995, [PERSON] and [PERSON] introduced a brand new concept--nanofluidics [2]. In 2002, [PERSON] and [PERSON] [3] measured the in-tube convective heat transfer coefficient of copper-water nanofluid under turbulent flow, and the experimental results showed that the addition of nanoparticles to the liquid significantly increased the in-tube convective heat transfer coefficient of the liquid. The flow and convective heat transfer characteristics of deionized water, Cu-water nanofluid and Al-water nanofluid, in a parallel semicircular microchannel heat sink were experimentally investigated by [PERSON] et al. [4]. It was found that the heat transfer effect of Cu-water nanofluid was better than that of Al-water nanofluid. In 2018, [PERSON] et al. [5] prepared three heat sinks with different channel structures using two different volume concentrations of nanofluid and distilled water, andtested their heat transfer characteristics. The results showed that the nanofluid significantly improved the thermal performance of the microchannel heat sink compared to distilled water. In 2022, [PERSON] et al. [6] conducted a numerical simulation study of the heat transfer characteristics of Cu-ethanol, Cu-ethylene glycol, and Cu-propylene glycol-based nanofluids in a wave-walled tube, and analyzed the effect of nanoparticle volume fraction \(\varphi\) on the heat transfer characteristics of the nanofluids. The results show that the thermal conductivity of the nanofluids was larger than that of the base fluid under the same conditions, and increased with the increase in \(\varphi\). At this stage, nanofluids are widely used in the field of enhanced heat transfer, such as in heat pipes, microchannels, heat sinks, and solar energy utilization [3; 4; 5; 6; 7; 8], and a few scholars have studied the application of nanofluids in the field of liquid-cooled data centers, plus nanofluids as a new class of heat transfer cooling workpiece, providing a theoretical basis for their application in liquid-cooled cabinets. Nanofluid cooling is an emerging and promising technology that can bring multiple implications to liquid-cooled data centers. Nanofluids have good heat transfer properties and can effectively absorb and transfer heat. Compared with traditional cooling media, nanofluid can cool heat-concentrated equipment more effectively and improve cooling efficiency. Due to the better heat transfer properties of nanofluids, the same cooling effect can be achieved using a relatively low temperature of the cooling medium, thus reducing the cost of energy used for cooling. Nanofluid cooling provides a higher cooling capacity, enabling data centers to support higher-density server deployments and improve resource utilization. Nanofluid cooling reduces heat build-up, thereby reducing the risk of thermal limiting and thermal shutdown.