資料中心兩相熱虹吸式冷卻系統熱負荷影響研究

The effect of variable heating load on Separated Two-Phase Thermosiphon Loops used to cool datacenter servers

蘇茂凡(Mohammed W.I. Sulaiman)

指導教授 ： 王啟川

國立交通大學/工學院/機械工程系所/碩士(2019年)

摘要

This study aims to investigate energy saving potential by using a separate two-phase thermosiphon loop (STPTL) as a free cooling technology in the data center. The thermosiphon heat exchanger takes the form as a fin-and-tube configuration and is installed when exiting the data rack. Based on previous discussions, the following conclusions can be drawn:
1. The experimental results indicate that the energy saving increases with the rise of filling ratio and heating load. However, optimum energy savings can be achieved at a filling ratio of 90%. A substantial energy savings of 49% can be achieved at the filling ratio of 90% and heating load 6 kW.
2. It is clear from results that a slightly better energy saving was obtained at low ambient temperature when the heating load was concentrated at heaters 3 and 4, the results were obviously better than the uniform heating load. while the energy saving becomes close at high ambient temperature when the heating load was concentrated at different positions or uniform.
3. The best power consumption was obtained at low fans velocity. The air flow rate increases with increase fans speed; accordingly, the surface temperature of the thermosiphon will be lower, which will cause a reduction in nucleate boiling and the heat transfer coefficient, thus the amount of heat absorbed by thermosiphon also decreases.
4. The results of the power consumption of AC (Pac) when two STPTL are working together showed that the energy saving is improved with the rise of ambient temperature, the energy saving reaches about (25% ± 2%). While a decline in energy saving for the whole system showed, with increasing the ambient temperature, because of the increased rate of heat transfer through the STPTL, which leads to an increase in energy consumed by chiller to cool water (Pch). The energy saving reaches about (19% ± 4%).
5. A lower overall thermal resistance occurs at high filling ratios, a higher ambient temperature, and higher heating load. It is found that the overall thermal resistance at the high filling ratios for the thermosiphon loop is converging with another research close to filling ratio and heating load with a different working fluid.

關鍵字

資料中心之 ； 兩相 ； 可变加热负荷 ； 熱虹吸設 ； 分开的循环 ； 節能

並列摘要

The energy consumption in datacentre accounts for about 2% of the global electricity utilization. Among the electricity being used, half of them is attributed to cooling requirement. Hence, reducing energy consumption of datacentres cooling equipment becomes an immediate requirement and the energy consumption can be significantly improved through free cooling technologies. To meet the above energy-saving demand, an integrated system of mechanical refrigeration and separated two-phase thermosiphon loop (STPTL) is proposed for datacentre cooling. Two simulated data racks were used for this study, in which one rack is attached with fin-and-tube thermosiphon heat exchanger and another one is without thermosyphon loop. The data racks were cooled by CRAC unit (computer room air conditioning unit). The utilization of thermosiphon loop helps in reducing the compressor load of CRAC partially and thus leads to the potential energy-saving. The experimental investigation on energy saving through thermosiphon loop was carried out under three ambient conditions (20 C, 23 C and 27 C) for the various filling ratios of 30-90% and at different heating loads ranging between 1.5 kW and 6 kW. Through experimental study, it was found that the energy saving increases with the filling ratio and up to 49% of energy saving of the CRAC can be achieved through thermosiphon assisted cooling. It was also found that the energy saving was in line with the rise of system pressure. The effect of uniform and concentrated heating load on energy saving was studied under various ambient conditions for the 90% filling ratio and 1.5 kW heating load. The results showed that the performance under concentrated heating load, in the upper thermosiphon was slightly better than the others. The influence of air flow rate was also investigated under various ambient temperatures for 90% filling ratio and a heating load of 6 kW, the results revealed that the lower flow rate performance are comparatively better than the higher flow rates. The study on influence of use of two STPTL indicated that 16–22% energy saving can be achieved at 90 % filling ratio and 6 kW heating load under all the studied ambient conditions. A lower thermal resistance encountered at the higher filling ratios, ambient temperature, and heating load.

並列關鍵字

datacenter ； two-phase flow ； variable heating loads ； thermosiphon ； separated loop ； energy saving

參考文獻

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