视角转变 | 从零开始思考数据中心制冷
更多干货等你发现！
返璞归真-重新思考数据中心制冷
Back to Basics: rethinking data center cooling
过去十几年的工程原理能否成为解锁数据中心冷却方式未来的关键？
Could a decades old engineering principle be the key to unlocking the future of data center cooling?
February 15, 2021
由于近些年数据使用量呈指数级增长，数据中心对于日常生活正变得越来越重要。无论是网络游戏、远程教育、虚拟会议或者最基本的网购，每天都有数十亿人在使用互联网。在2020年，Domo估测互联网覆盖了全世界59%的人口，相当于45.7亿人！
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!
所有的互联网应用都需要巨大容量的数据中心支撑，需要服务器24x7不间断的工作进行路由通信以及进程处理。在数据中心设计、服务器技术、软件开发等方面的发展使数据中心的能效变得更高，因此有人指出全球数据中心能耗的增长速度比三四年前预期的要慢很多。但数据中心仍然消耗了世界上大量的能源。所以，在数据中心未来的运营过程中需要持续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.
事实：服务器产生热量，而为了维持服务器正常运行必须消除这些热量。
Fact: Servers generate heat, and this heat must be removed in order to maintain operation.
近些年，我们已经发现很多为数据中心散热的方法。随着服务器技术的发展，使用直膨制冷的传统机房空调也变的更为高效，包括利用室外空气的经济器来直接或间接地冷却机房。
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.
大多数经济器都利用了水的蒸发冷却。虽然蒸发冷却能够显著地提高经济器的效率，但由于世界上大多数地区缺水现象正在加剧，水资源利用已经成为工业界关心的主要问题。以微软为代表的很多企业开始提倡“水中和”，致力于降低包括数据中心在内所有业务领域的水资源的使用。
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.
虽然使用室外冷风、冷水等自然冷源能够实现更高的能源效率，但它们同时也对运营商们提出了更大的挑战。因此，数据中心设计人员已经开始重新思考冷却方式，并且会使用一些更传统的方式，比如风冷冷水机组。近年来，冷水机组在节能技术方面确实有一些进展，但其产生的节能量是否足够使得高额冷机投入显得合理？在不使用水或者室外新风直接进入数据中心前提下，或许我们能够使用物理学原理来寻找更有效的数据中心散热方法。
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.
数据中心冷却的实质就是热量传递。服务器耗电并产生热。为了服务器正常运行，这些热量必须通过流体（气体或液体）带走。这个过程能够通过很多种方式实现，但它真的能够仅通过自然驱动力来完成吗？例如，在不使用耗电的机械设备的前提下，热量是否能够通过介质流向外部散热设备？
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?
热虹吸现象图示-Munters
Illustration of a thermosyphon– Munters
答案是肯定的，这种装置通过相变和重力的驱动，也叫热虹吸管或重力热管。自然对流是一种热量传递方式，传递过程中流体运动不是通过外力产生，而是由流体内部的密度差产生。大多数情况下自然对流都会引起自然循环或系统持续循环流动的能力，这种循环被流体气液相变和重力所驱动。
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.
热虹吸管提供了一种热被动交换方式，它基于自然对流原理，并且循环过程中不需要额外的机械泵提供动力。换句话说，重力作用充当系统动力。热虹吸管在制冷领域并不是一个新概念。它们已经被广泛应用在很多领域中，包括太阳能供暖系统和冷机经济器中。
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.
那为什么不在数据中心中使用热虹吸管呢？
So why not use thermosyphons in Data Centers?
Munters SyCool Split 400 kW System
Munters SyCool 400KW分离式系统
事实证明，在过去的几年中使用热虹吸管用于数据中心制冷已经进行过很多的实验，尤其是在美国国家可再生能源实验室（NREL）的数据中心。在2020年2月NREL宣布通过在科罗拉多州戈登市的数据中心中使用热虹吸管制冷每年可节省1150000加仑水。但是直到现在，除了带有经济器的冷机，数据中心制冷设备供应商通常不会使用热虹吸管，因为它的效率并没有那么高。
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率先推出了使用热虹吸科技的集成空气处理器系统，名为SyCool。从那以后，Munters将一种分离式系统部署在数据中心（如图），并通过上千小时的测试实验来进一步研究热虹吸管。与传统的干式机械制冷系统相比，Munters的SyCool具有更一流的节能效果，并且证明热虹吸管能够在不消耗水资源的情况下，有效地减少数据中心散热引起的电力消耗。
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.
随着数据中心逐渐地成为全球关键基础设施的一部分，工业领袖们将会努力寻求运营数据中心更高效的方法。功率密度将随着服务器升级持续增长，并且冷却方式可能会更多地由风冷向液冷转变。随着液冷广泛应用在工业领域，热虹吸技术能被当作一种更高效散热的方法利用。这可以通过一个制冷剂-液体热交换器来耦合热虹吸管系统和液冷系统实现。
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.
有时候答案就是很简单，通过运用一些古老的原理就可以做出解决巨大挑战的创新。当谈及数据中心制冷时，热虹吸也许是数据中心向着可持续发展新篇章前进的新动力。
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.
翻译：
苏鹏伟
捷通智能科技股份有限公司 技术经理
DKV（Deep Knowledge Volunteer）精英成员
校对：
田瑞杰
中国民航信息集团公司 高级工程师
DKV（Deep Knowledge Volunteer）精英成员
公众号声明：