Enhanced immersion two-phase liquid cooling for data centre thermal management

• Main Author: Tan, Zun Yuan
• Other Authors: Fei Duan
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Mechanical engineering::Energy conservation
• Online Access: http://hdl.handle.net/10356/78597
• Institution: Nanyang Technological University

The stunning growth of technology in recent years has exacerbated the rise in energy consumption for cooling in data centres. Besides rising population and growing of metropolis, advance in IT and increasing adoption of internet of things such as big data, AI and cloud computing by governments, corporates and individuals have vastly increase the information stored and transferred. As a result, higher cooling capacity is necessary to remove excessive heat dissipation generated by servers to avoid detrimental effects on the quality and lifetime of electronic components. Current prevailing traditional air-cooling methods are inefficient as they consume impractical amount of energy to remove heat loads at a limited rate. An alternative cooling method is therefore introduced in this report to overcome this problem. The first part of this report describes the pool boiling experiments carried out on amorphous and crystallised TiO2 nanotube coated titanium surfaces measuring 10mm x 2mm in area using HFE 7100 bath fluid under atmosphere pressure. Results shows that both surfaces achieved enhanced nucleate heat transfer performance as compared to the bare surface and amorphous TiO2 nanotube coated surface attained the best results. Amorphous TiO2 nanotube coated surface attained a maximum heat transfer coefficient and critical heat flux of 2.07 W/cm2K and 39.62 W/cm2, respectively while crystallised TiO2 nanotube coated surface achieved 1.57 W/cm2K and 37.24 W/cm2, respectively. Average bubble diameters and departure frequencies measured for amorphous and crystallised TiO2 nanotube coated surface are 0.46 mm, 184 bubble/s and 0.42 mm, 233 bubble/s, respectively. Enhancement is attributed to increased nucleation site density and capillary effect due to amorphous and crystallised TiO2 nanotube. In the second part of this report, an industrial scale, 32kW design load two-phase immersion cooling system with two condensers (top and submerged) are built and assessed for its cooling performance under different heat loads using HFE 7100 as the bath fluid. Based on the results attained, heat removal contribution by the top condenser rises past 50% as compared to that by both condensers and the system coefficient of performance increases from 0.48 to 1.58 as the heat load increases. Three processor junction temperatures attained at the highest heat load of 8.87kW were 65.6, 73 and 71.4°C implying a limiting factor for further increase in heat load. Further studies can be done to investigate long term boiling effect on the durability of TiO2 nanotube coated surfaces. Also, two-phase immersion cooling studies can be done at higher heat load using electronic components with its surface coated with TiO2 nanotube to assess the system highest performance under practical operating temperature.