The improved efficiency of mineral oil may offer simplicity in facility design compared to traditional air cooling and provide a means for cost savings. Despite its improved cooling efficiency and cost savings, a mineral oil immersion cooling technique is still not widely implemented and original equipment manufacturers are reluctant to jeopardize sales of existing air-based cooling system equipment. Only compelling physics regarding thermal performance of direct immersion cooling is not enough for data center operators. Many uncertainties and concerns persist regarding the effects of mineral oil immersion cooling on the reliability of information technology (IT) equipment both at the component and chassis level. This paper is a first attempt at addressing this challenge by reviewing the changes in physical and chemical properties of IT equipment materials like polyvinyl chloride (PVC), printed circuit board (PCB), and capacitors and characterizes the interconnect reliability of materials. The changes in properties of a mineral oil like kinematic viscosity and dielectric strength are also cited as important factors and discussed briefly. The changes in mechanical properties like elasticity, hardness, swelling, and creep are being shown in the paper for thermoplastic materials. The chemical reaction between material and mineral oil as a function of time and temperature is also conferred. The literature gathered on the subject and quantifiable data gathered by the authors provide the primary basis for this research document.

Complete immersion of servers in dielectric mineral oil has recently become a promising technique for minimizing cooling energy consumption in data centers. However, a lack of sufficient published data and long-term documentation of oil immersion cooling performance make most data center operators hesitant to apply these approaches to their mission critical facilities. In this study, a single server was fully submerged horizontally in mineral oil. Experiments were conducted to observe the effects of varying the volumetric flow rate and oil inlet temperature on thermal performance and power consumption of the server. Specifically, temperature measurements of the central processing units (CPUs), motherboard (MB) components, and bulk fluid were recorded at steady-state conditions. These results provide an initial bounding envelope of environmental conditions suitable for an oil immersion data center. Comparing with results from baseline tests performed with traditional air cooling, the technology shows a 34.4% reduction in the thermal resistance of the system. Overall, the cooling loop was able to achieve partial power usage effectiveness (pPUECooling) values as low as 1.03. This server level study provides a preview of possible facility energy savings by utilizing high temperature, low flow rate oil for cooling. A discussion on additional opportunities for optimization of information technology (IT) hardware and implementation of oil cooling is also included.

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