網路資料中心機櫃能源使用效率最佳化分析

Abstract

本研究將以兩種RCI指標（RCIHI、RCILO）搭配計算流體力學套裝軟體FLUENT分析機房熱流場，並以改造機房設計做為降低耗電量的思維，提出針對機房設計所需的參考標準。研究個案分為兩部份，方案1與方案2。方案1包含51個機櫃，需要306kW（每櫃6kW）冷卻能力，方案2包含82個機櫃，需求492kW冷卻能力。方案1與方案2都是CRAC搭配XD系統提供冷卻能力。對每個方案來說，首先從設計CRAC及XDH全開啟的參考方案作為比較基準。接著，進行不同CRAC與XDH開啟/關閉組合的參數研究。再者，結合模擬結果，利用RCIHI與RCILO來評估機房健康程度。在不同情境進行分析，靠近CRAC處均有RCIHI不良發生，由於受到CRAC送風時造成的顯著負壓導致熱通道之熱流場受到壓力場之影響而汙染附近冷通道，導致冷卻能力不佳。全使用XDH並無法解決上方之熱蓄積之問題，隨之而來的熱沉降之問題將會考驗機櫃上端之RCI品質，在角落之無風處亦然會有此一問題，均因沒有全區流場作熱循環所致。在任何改善設計或是加設冷卻設備等，應先有適當的模擬評估，且同樣的手法不可直接套用在不同廠區，受到冷卻設備不同以及幾何外型等，先經由模擬驗證是較佳的選擇。最後，提出幾個建議給網路資料中心的設計者。

This study employs two RCI indices (RCIHI and RCILO) combined with the fluid dynamics software FLUENT to analyze the thermal-and-flow fields in an IDC. It supports the reconstruction of an IDC room to reduce power consumption, and proposes standards for energy-saving design. The case study is divided into parts, Plan 1 and Plan 2. Plan 1 contains 51 racks, requiring 306kW (6kW per rack) cooling capability, and Plan 2 contains 82 racks, needing 492kW cooling capability. Both Plan 1 and Plan 2 combine CRAC with XD system to supply the cooling capability. For each plan, it begins with its own reference case, whose designed CRACs and XDHs are all at full power, to serve as a comparison base. Next, the parametric studies are carried out respectively under different on/off combinations of CRACs and XDHs. Furthermore, incorporating with simulation results, RCIHI and RCILO are employed to evaluate the healthy level of equipment room. The analyses are performed under different conditions. The areas surrounding the CRAC are characterized by deficient RCIHI. It is resulted from the evident negative pressure gradient caused by CRAC ventilation because the heat flow from the hot aisle contaminates the neighboring cold aisle due to the extreme pressure difference that in turn leads to inferior cooling capabilities. Exclusive use of XDH does not solve the problem of heat gathering in the upper areas of the room. When the heat descends, it will pose a challenge to the RCI quality of the area above the equipment; corners that are beyond the air flow field are also problematic. Both problems are caused by the lack of air recirculation flow. It is thus evident that if improvements or additional cooling equipments are to be installed, it is necessary to run a simulation to evaluate its feasibility. Additionally, the same method cannot be directly incorporated into different environments because the equipments and the geometrical conditions are different. Thus, it is necessary to first simulate the conditions before making any changes. Eventually, several suggestions are proposed for Internet Data Center designers.