深知社小课堂一文看懂机械制冷小青虫的梦
机械制冷
mechanical refrigeration
加入九三学社Apri 15, 2022 By Gavin Wright
译 者 说
煎糍粑传统的机械制冷，不会随着新技术的涌现而退出市场，总会有一席之地。
肖爱国什么是机械制冷?
What is mechanical refrigeration?
机械制冷就是通常所说的制冷或空调，是一种利用人造热交换系统将热量从一处移除的过程。机房空调(CRAC)是数据中心最常用的制冷形式。
Mechanical refrigeration, often referred to simply as refrigeration or air conditioning, is a pro
cess by which heat is removed from a location using a human-made heat exchange system. In a data center, computer room air conditioning (CRAC) is the most common u of refrigeration.
机械制冷的原理Principles of mechanical refrigeration
机械制冷的基本物理原理是热力学第一定律。这条定律表明，能量（这里指热能）不会凭空产生，也不会凭空消失，只能从一处转移到另一处,且需通过做功来实现。在制冷过程中，热能从一个不需要它的位置被吸收，经过一个过程后，传递到另一个位置被排出或辐射出去。引发热传递所需的能量是由泵或电机提供的，而不是由电或化学过程提供的，因此称为机械制冷。精神家园
The underlying physics principle of mechanical refrigeration is the first law of thermodynamics. This law states that energy -- or heat in this ca -- cannot be created or destroyed, only transferred from one place to another, and that it requires work to cau the transfer of energy. In a refrigeration process, the heat energy is absorbed in one location where it is not wanted, and through a process, it is pumped to another locati
on where the heat can be expelled or radiated away. The work energy required to cau the heat transfer is provided by a pump or motor, not from an electrical or chemical process, so it is referred to as mechanical refrigeration.
上图为一个直膨式机房空调(CRAC)系统的工作循环
Diagram illustrating how a cycle in a a direct expansion computer room air conditioning (CRAC) system works
最常见的机械制冷方式是蒸汽压缩循环，也叫朗肯循环，是利用制冷剂的循环来吸热和放热。制冷剂的工作原理是，液体沸腾或蒸发时会吸热，蒸汽凝结时会放热。利用制冷剂的沸点低于室温的特点，来达到冷却效果。
The most common form of mechanical refrigeration is the vapor compression cycle, also known as a rever-Rankine cycle. It us a refrigerant that is circulated to absorb and expel the heat. The refrigerant operates on the principle that heat is absorbed when a liquid boils or evaporates and that heat is relead when a vapor condens. The refrigerants have below-room temperature boiling points to enable a cooling effect.
在典型的蒸汽压缩式制冷机中，高压液态制冷剂首先被强制通过膨胀阀进入蒸发器。在低压蒸发器中，液态制冷剂从周围空气中吸收热量沸腾变成蒸汽。之后，高温蒸汽通过压缩机或泵被输送至高压冷凝器或盘管。冷凝器的高压使制冷剂凝结成液态，排出热量，排热过程通常采用一种典型的散热器。最后，液态制冷剂再次通过膨胀阀返回，并继续重复此循环。
In a typical vapor compression refrigerator, the high-pressure liquid refrigerant is first forced through an expansion valve. It then enters a lower pressure ries of tubes called the evaporator, where the liquid refrigerant boils. The boiling action caus it to absorb heat from the air around the evaporator as it turns to a vapor. The heated vapor then goes through a compressor or pump that forces it into the higher-pressure condenr tubes or coil. In the condenr, the high pressure caus the refrigerant to conden back into a liquid, which expels the heat, typically to a radiator of some sort. The liquid refrigerant is now ready to go back through the expansion valve again and repeat the process.
制冷的另一个效果是降低湿度或使冷空气变干，此功能在工业中有很多应用。蒸发器盘管上结冰可能导致性能问题，所以系统必须设计成能收集蒸发器盘管上形成的冷凝水。
An additional effect of refrigeration is that it reduces the humidity or dries the cooler air. This has many uful industrial applications. Systems must be designed to collect water condensation that forms on the evaporator coils. It is also possible that ice can form on the evaporator coils, causing performance issues.
上图为冷凝器CRAC制冷单元和水冷循环工作
Diagram illustrating how condenr water CRAC unit refrigeration and water cooling cycles work
数据中心机械制冷Mechanical refrigeration in a data center
电气设备会发热，废热是数据中心暖通（HVAC）系统设计要解决的主要问题。由于数据中心中有大量计算机设备紧密排列，产生的大量废热远远超过了自身被动处理的能力，且湿度过高也会损坏设备，因此需要采用机械制冷。如果数据中心或计算机机房不主动冷却，
就可能很快变得非常热，从而损坏计算机部件。
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Waste heat is a major concern in data center heating, ventilation and air conditioning (HVAC) designs since electronics generate heat. Becau data centers have many computers packed tightly together, they generate massive amounts of waste heat, much more than can be handled through passive means. Additionally, high humidity can damage computers. Therefore, mechanical refrigeration is required. If a data center or computer room is not actively cooled, it can quickly become so hot that the computer components can become damaged.
在传统数据中心设计中，服务器本身是风冷形式，将热量排放到周围空气中。大型CRAC空调单元可以冷却和除湿数据中心内的空气。通常每个数据中心都有一个以上的CRAC单元冗余，这样就可以在不造成过热的情况下进行维护。
职客
In traditional data center designs, the rvers themlves are air-cooled and expel their heat into the surrounding air. A large CRAC unit cools and dehumidifies the air inside the data center. Typically, more than one CRAC unit is in each data center to enable redunda
隐隐约约的意思ncy and so that they can be maintained without causing excessive heat buildup.
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多数情况下，CRAC空调将冷却的空气送入数据中心架空地板层，并在需要的位置设置带百叶的地板，使冷气可以从服务器机架的进气口进入。理想的做法是将服务器机架放置在通道中，使其风扇的进出风口相对，形成热冷通道。之后，热空气被天花板上的空气处理器吸入。
