CFD simulation study of flow equalisation plate model in single-phase immersion liquid cooling for servers

Abstract

Immersion liquid cooling is progressively being adopted for server cooling applications within data centers. Uneven coolant distribution in liquid-cooled cabinets may cause large temperature difference between servers under some extreme conditions, prompted this study on a flow equalization plate structure. Firstly, the servers, the cabinet and the flow equalisation plate were modelled using Ansys Icepak software, and then the effects of holes radii, inlet layout configurations, and the number of holes on the flow distribution of the FC-40 coolant and the temperature control across servers was investigated. The results indicate that the smaller radii is beneficial in balancing the flowrate within the holes of the flow equalization plate by increasing the flow resistance, yielding a maximum temperature difference and a maximum temperature standard deviation of 2.1 °C and 0.8 °C at r = 7.5 mm. However, excessively small radii can lead to higher internal pressures and flow resistance. With larger hole radii, temperature control is significantly influenced by the inlet flowrate. As the flowrate increases, ΔT and Tsd also increase, reaching up to 3.8 °C and 1.3 °C at r = 12.5 mm, respectively. Larger hole radii result in smaller coolant flowrate, leading to lower convective heat transfer coefficient and higher server temperature. Locating inlets on one side creates large low-velocity vortex areas, disrupting server cooling, while center placement enhances thermal performance. When the number of holes is 18, the hole spacing increases, which leads to an increase in the flowrate in the holes and an increase in the convective heat transfer coefficient, which improves the thermal performance factor ε to 1.04.