返璞歸真-重新思考數(shù)據(jù)中心制冷

Back to Basics: rethinking data center cooling

過去十幾年的工程原理能否成為解鎖數(shù)據(jù)中心冷卻方式未來的關(guān)鍵？

Could a decades old engineering principle be the key to unlocking the future of data center cooling?

February 15, 2021 

由于近些年數(shù)據(jù)使用量呈指數(shù)級(jí)增長，數(shù)據(jù)中心對(duì)于日常生活正變得越來越重要。無論是網(wǎng)絡(luò)游戲、遠(yuǎn)程教育、虛擬會(huì)議或者最基本的網(wǎng)購，每天都有數(shù)十億人在使用互聯(lián)網(wǎng)。在2020年，Domo估測互聯(lián)網(wǎng)覆蓋了全世界59%的人口，相當(dāng)于45.7億人！

With the exponential growth of data usage in recent years, data centers are becoming more and more critical to everyday life. Whether it’s online gaming, remote schooling, virtual conferences, or basic shopping, billions of people access the internet every day. In 2020, Domo estimated the internet reaches 59 percent of the world’s population, or a whopping 4.57 billion people!

所有的互聯(lián)網(wǎng)應(yīng)用都需要巨大容量的數(shù)據(jù)中心支撐，需要服務(wù)器24x7不間斷的工作進(jìn)行路由通信以及進(jìn)程處理。在數(shù)據(jù)中心設(shè)計(jì)、服務(wù)器技術(shù)、軟件開發(fā)等方面的發(fā)展使數(shù)據(jù)中心的能效變得更高，因此有人指出全球數(shù)據(jù)中心能耗的增長速度比三四年前預(yù)期的要慢很多。但數(shù)據(jù)中心仍然消耗了世界上大量的能源。所以，在數(shù)據(jù)中心未來的運(yùn)營過程中需要持續(xù)追求更高能效的方法。

All of this internet usage requires significant data center capacity, where servers work 24x7 to route internet traffic and process transactions. Advancements in data center design, server technology, and software development have all contributed to more energy efficient data centers in recent years, leading some to suggest the global energy usage is growing at a much slower rate than anticipated just three to four years ago. However, data centers still consume a significant amount of the world’s energy, and thus the need to continue pursuing more energy efficient methods for operating the data centers of the future.

事實(shí)：服務(wù)器產(chǎn)生熱量，而為了維持服務(wù)器正常運(yùn)行必須消除這些熱量。

Fact: Servers generate heat, and this heat must be removed in order to maintain operation.

近些年，我們已經(jīng)發(fā)現(xiàn)很多為數(shù)據(jù)中心散熱的方法。隨著服務(wù)器技術(shù)的發(fā)展，使用直膨制冷的傳統(tǒng)機(jī)房空調(diào)也變的更為高效，包括利用室外空氣的經(jīng)濟(jì)器來直接或間接地冷卻機(jī)房。

Over the years, we’ve seen many methods for rejecting data center heat. As server technology evolved, traditional computer room air conditioning (CRAC) using direct expansion refrigeration evolved to more energy efficient cooling methods, including economizers, where outdoor air is used, either directly or indirectly, to cool data halls.

大多數(shù)經(jīng)濟(jì)器都利用了水的蒸發(fā)冷卻。雖然蒸發(fā)冷卻能夠顯著地提高經(jīng)濟(jì)器的效率，但由于世界上大多數(shù)地區(qū)缺水現(xiàn)象正在加劇，水資源利用已經(jīng)成為工業(yè)界關(guān)心的主要問題。以微軟為代表的很多企業(yè)開始提倡“水中和”，致力于降低包括數(shù)據(jù)中心在內(nèi)所有業(yè)務(wù)領(lǐng)域的水資源的使用。

Many of these economizer solutions use water through evaporative cooling. While evaporative cooling can significantly enhance the efficiency of economizing options, water usage has become a major concern in the industry due to a growing shortage of water in many regions of the world. Many companies, such as Microsoft, have begun broad initiatives to become “water neutral” in an effort to drive down overall water usage in all of their facilities, including data centers.

雖然使用室外冷風(fēng)、冷水等自然冷源能夠?qū)崿F(xiàn)更高的能源效率，但它們同時(shí)也對(duì)運(yùn)營商們提出了更大的挑戰(zhàn)。因此，數(shù)據(jù)中心設(shè)計(jì)人員已經(jīng)開始重新思考冷卻方式，并且會(huì)使用一些更傳統(tǒng)的方式，比如風(fēng)冷冷水機(jī)組。近年來，冷水機(jī)組在節(jié)能技術(shù)方面確實(shí)有一些進(jìn)展，但其產(chǎn)生的節(jié)能量是否足夠使得高額冷機(jī)投入顯得合理？在不使用水或者室外新風(fēng)直接進(jìn)入數(shù)據(jù)中心前提下，或許我們能夠使用物理學(xué)原理來尋找更有效的數(shù)據(jù)中心散熱方法。

While using natural resources such as outdoor air and water provide high energy efficiency, these resources also present challenges for companies operating data centers. As a result, data center designers have been rethinking their cooling strategies, often defaulting back to more traditional methods such as air-cooled chillers. Recent advancements in chiller technology offer energy savings, but is that enough, and do the savings justify the higher cost of installing chiller plants? Perhaps, we can use the principles of physics to find even more efficient methods for rejecting data center heat naturally, without the use of water or the need to introduce outdoor air into the data center.

數(shù)據(jù)中心冷卻的實(shí)質(zhì)就是熱量傳遞。服務(wù)器耗電并產(chǎn)生熱。為了服務(wù)器正常運(yùn)行，這些熱量必須通過流體（氣體或液體）帶走。這個(gè)過程能夠通過很多種方式實(shí)現(xiàn)，但它真的能夠僅通過自然驅(qū)動(dòng)力來完成嗎？例如，在不使用耗電的機(jī)械設(shè)備的前提下，熱量是否能夠通過介質(zhì)流向外部散熱設(shè)備？

Cooling a data center is all about heat transfer. Electronics (servers) generate heat. This heat must be removed from servers through a fluid (air or liquid) in order for the servers to operate. This can be accomplished through several methods, but could it be done naturally by simply using the forces of nature? For example, could the heat transport medium flow to externally mounted heat rejection devices without the use of power consuming mechanical devices?

熱虹吸現(xiàn)象圖示-Munters

Illustration of a thermosyphon– Munters

答案是肯定的，這種裝置通過相變和重力的驅(qū)動(dòng)，也叫熱虹吸管或重力熱管。自然對(duì)流是一種熱量傳遞方式，傳遞過程中流體運(yùn)動(dòng)不是通過外力產(chǎn)生，而是由流體內(nèi)部的密度差產(chǎn)生。大多數(shù)情況下自然對(duì)流都會(huì)引起自然循環(huán)或系統(tǒng)持續(xù)循環(huán)流動(dòng)的能力，這種循環(huán)被流體氣液相變和重力所驅(qū)動(dòng)。

The answer is yes, through the driving force of phase change and gravity, also known as thermosyphon (or thermosiphon). Natural convection is a type of heat transfer, in which the fluid motion is not generated by an external source but rather by some parts of the fluid being heavier than other parts. In most cases this leads to natural circulation, or the ability of a fluid in a system to circulate continuously, propelled by the fluid changing phase from vapor to liquid, and by gravity.

熱虹吸管提供了一種熱被動(dòng)交換方式，它基于自然對(duì)流原理，并且循環(huán)過程中不需要額外的機(jī)械泵提供動(dòng)力。換句話說，重力作用充當(dāng)系統(tǒng)動(dòng)力。熱虹吸管在制冷領(lǐng)域并不是一個(gè)新概念。它們已經(jīng)被廣泛應(yīng)用在很多領(lǐng)域中，包括太陽能供暖系統(tǒng)和冷機(jī)經(jīng)濟(jì)器中。

Thermosyphons provide a method of passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump. In other words, gravity does the work. Thermosyphons are not a new concept for cooling. They are widely used as a cooling method in many applications, including solar heating systems and chiller economizing.

那為什么不在數(shù)據(jù)中心中使用熱虹吸管呢？

So why not use thermosyphons in Data Centers?

Munters SyCool Split 400 kW System

Munters SyCool 400KW分離式系統(tǒng)

事實(shí)證明，在過去的幾年中使用熱虹吸管用于數(shù)據(jù)中心制冷已經(jīng)進(jìn)行過很多的實(shí)驗(yàn)，尤其是在美國國家可再生能源實(shí)驗(yàn)室（NREL）的數(shù)據(jù)中心。在2020年2月NREL宣布通過在科羅拉多州戈登市的數(shù)據(jù)中心中使用熱虹吸管制冷每年可節(jié)省1150000加侖水。但是直到現(xiàn)在，除了帶有經(jīng)濟(jì)器的冷機(jī)，數(shù)據(jù)中心制冷設(shè)備供應(yīng)商通常不會(huì)使用熱虹吸管，因?yàn)樗男什]有那么高。

It turns out experiments in thermosyphon cooling for data centers have been conducted over the past few years, most notably at a US National Renewable Energy Laboratory (NREL) data center. In February 2020, NREL reported saving 1.15 million gallons of water over a year by utilizing thermosyphon cooling at a data center in Golden, Colorado. However, until now, manufacturers of data center cooling solutions generally have not harnessed the benefit of thermosyphon’s, except for use in chiller based economizers, which have not proved to be that efficient.

在2018年，Munters率先推出了使用熱虹吸科技的集成空氣處理器系統(tǒng)，名為SyCool。從那以后，Munters將一種分離式系統(tǒng)部署在數(shù)據(jù)中心（如圖），并通過上千小時(shí)的測試實(shí)驗(yàn)來進(jìn)一步研究熱虹吸管。與傳統(tǒng)的干式機(jī)械制冷系統(tǒng)相比，Munters的SyCool具有更一流的節(jié)能效果，并且證明熱虹吸管能夠在不消耗水資源的情況下，有效地減少數(shù)據(jù)中心散熱引起的電力消耗。 

In 2018, Munters first introduced thermosyphon technology in a packaged air handler system for data center cooling, called SyCool. Since that time, Munters further developed the technology, through thousands of test hours, in a split system for deployment to data centers (see figure,). When compared to conventional dry mechanical cooling systems, Munters SyCool offers best-in-class energy savings, proving that thermosyphons can effectively be used to reduce the electrical energy required to reject data center heat without any use of water.

隨著數(shù)據(jù)中心逐漸地成為全球關(guān)鍵基礎(chǔ)設(shè)施的一部分，工業(yè)領(lǐng)袖們將會(huì)努力尋求運(yùn)營數(shù)據(jù)中心更高效的方法。功率密度將隨著服務(wù)器升級(jí)持續(xù)增長，并且冷卻方式可能會(huì)更多地由風(fēng)冷向液冷轉(zhuǎn)變。隨著液冷廣泛應(yīng)用在工業(yè)領(lǐng)域，熱虹吸技術(shù)能被當(dāng)作一種更高效散熱的方法利用。這可以通過一個(gè)制冷劑-液體熱交換器來耦合熱虹吸管系統(tǒng)和液冷系統(tǒng)實(shí)現(xiàn)。

As data centers increasingly become a part of the world’s critical infrastructure, industry leaders will strive to find methods for more efficient data center operation. Watt densities will continue to increase as server technology evolves and cooling methods may shift more toward liquid cooling as opposed to air cooling. As liquid cooling becomes more prevalent in the industry, thermosyphon technology can be utilized as a method to achieve high efficiency heat rejection. This can be achieved by coupling a liquid cooling system with a thermosyphon system through a refrigerant-to-liquid heat exchanger.

有時(shí)候答案就是很簡單，通過運(yùn)用一些古老的原理就可以做出解決巨大挑戰(zhàn)的創(chuàng)新。當(dāng)談及數(shù)據(jù)中心制冷時(shí)，熱虹吸也許是數(shù)據(jù)中心向著可持續(xù)發(fā)展新篇章前進(jìn)的新動(dòng)力。

Sometimes the answer is simple, and by applying age old principles, we can create new innovations to solve some of our biggest challenges. When it comes to cooling data centers, thermosyphons provide the motive “force” to drive the next chapter in a sustainable future for data centers.

翻譯：

蘇鵬偉

捷通智能科技股份有限公司 技術(shù)經(jīng)理

DKV（Deep Knowledge Volunteer）精英成員

校對(duì)：

田瑞杰

中國民航信息集團(tuán)公司 高級(jí)工程師

DKV（Deep Knowledge Volunteer）精英成員

公眾號(hào)聲明：