Shulou(Shulou.com)11/24 Report--

The original title: "it's so hot, who's going to upgrade my air conditioner!" "

Summer is hot, eating watermelons and blowing air conditioners on the net is a very pleasant thing. Have you ever thought that on the other side of the network, a large number of servers are serving us non-stop. They work 24 hours a day, and they can't do without air conditioning for a moment.

Today, the document will take you to learn about several typical cooling technologies in data centers.

1. Mechanical air-cooled refrigeration before 2005, belongs to the initial stage of the development of network business, the computing power of the data center is still relatively small, the data center mainly uses mechanical air-cooled air-conditioning refrigeration. The basic operation principle of this kind of air conditioner is the same as that of household air conditioning. it is mainly cooled by the mechanical work of the compressor to change the state of the refrigerant. the refrigeration principle is shown in the following figure.

1. The compressor compresses the gaseous refrigerant into a state of high temperature and high pressure.

2. When the high temperature and high pressure gaseous refrigerant passes through the condenser, because the ambient temperature is lower than the boiling point temperature of the refrigerant, it condenses into liquid and releases heat to the environment at the same time.

3. The liquid refrigerant from the condenser goes through the expansion valve to throttle and depressurize and enter the evaporator.

4. After entering the evaporator, because the ambient temperature is higher than the boiling point temperature of the refrigerant, the liquid refrigerant evaporates into a gaseous state, from environmental heat absorption to refrigeration purpose.

The above process is repeated, using the principles of condensation heat release and evaporation heat absorption in the process of gaseous and liquid conversion of refrigerants.

When mechanical air-cooled air conditioners are actually installed and deployed, condensers are usually deployed outdoors for heat dissipation, and evaporators, expansion valves and compressors are deployed indoors for equipment cooling. This is shown in the following figure.

Mechanical air-cooled air conditioner each unit is relatively independent control and operation, installation and maintenance is relatively simple, while the refrigeration efficiency is relatively low, outdoor units will also occupy a larger space.

two。 Chilled water refrigeration from 2005 to 2015, with the outbreak of Internet and mobile Internet services, the computing power of data centers increased, and chilled water systems began to be used gradually. Chilled water system on the basis of mechanical air-cooled refrigeration cycle, superimposed cooling water cycle and chilled water cycle to achieve refrigeration, the principle is shown in the following figure.

1. Refrigerant cycle: the same as mechanical air-cooled refrigeration, cooling at the evaporator produces cold capacity, and heating at the condenser produces heat.

2. Chilled water cycle: the water in the water pump drives the pipe to exchange heat with the evaporator to get the frozen water, and the chilled water carries the cooling capacity to the air treatment unit.

3. Air cycle: the air handling unit exchanges heat with frozen water to get cold air and supply air indoors to achieve the purpose of refrigeration.

4. Cooling water circulation: the water in the water pump drives the pipe to exchange heat with the condenser to get the cooling water. The cooling water carries heat to the cooling tower, and the heat is released through the cooling tower.

When the chilled water air conditioning system is actually installed and deployed, compressors, condensers, evaporators and expansion valves are usually integrated in the building for cooling, and cooling towers are deployed on the roof to dissipate heat. This is shown in the following figure.

The chilled water system has larger refrigeration capacity, higher energy efficiency and stability, and is centralized for multiple ends of cooling. At the same time, due to the large number of water pipes, a large number of welding operations are required for installation and deployment.

3. Indirect evaporative refrigeration from 2005 to 2015, with the outbreak of Internet and mobile Internet services, the computing power of the data center further increased, and the indirect evaporative refrigeration system began to be used gradually. Indirect evaporative refrigeration realizes the heat exchange between external natural cold air and hot return air in data center through non-direct contact heat exchanger. The principle is shown in the following figure.

1. The external natural air (secondary air) enters the air from the bottom, passes through the heat exchanger, and comes out from the top.

2. The air in the data center (primary air) enters the air horizontally and passes through the heat exchanger and the secondary air to achieve the purpose of refrigeration.

Indirect evaporative refrigeration and air conditioning integration has a variety of working modes, providing different refrigeration levels.

Dry mode

When the temperature of the secondary air is low, it can directly exchange heat with the primary air to achieve cooling.

Wet mode

When the temperature of the secondary air is high, the secondary air is humidified by spraying water to cool the secondary air after evaporation, and then heat exchange with the primary air to achieve cooling.

Mixed mode

On the basis of dry mode and wet mode, the traditional mechanical air cooling system is added as a means of auxiliary refrigeration.

When indirect evaporative refrigeration air conditioners are actually installed and deployed, they are usually deployed on the side or top of the data center. This is shown in the following figure.

Indirect evaporative refrigeration combines natural cold source refrigeration and evaporative refrigeration technology to increase the natural cooling time and further improve the refrigeration efficiency. At the same time, the products based on indirect evaporation refrigeration are gradually prefabricated and modular, and the installation and deployment is more convenient.

4. When it comes to liquid cooling, do you think of the practice of companies such as Google and Microsoft putting their data centers directly in the sea or in mountain caves, or DIY's cool liquid-cooled chassis? After 2020, with the continuous growth of computing power in the data center, the traditional air-cooled heat dissipation has been close to the bottleneck, and the liquid cooling technology with higher heat dissipation efficiency began to rise gradually. The principle is shown in the following figure.

There are usually three ways of liquid cooling:

Cold plate liquid cooling

The heat of the heating device is transferred indirectly to the coolant in the circulating pipeline through the liquid cooling plate, and the heat is taken away.

Immersion liquid cooling

The coolant is directly used as the heat transfer medium, and the heating device is completely "bubbled" in the coolant and through direct contact heat exchange.

Spray liquid cooling

Dissipate heat for the heating device by spraying coolant.

When the liquid-cooled refrigeration system is actually installed and deployed, the cooling tower is usually deployed outdoors, and the CDU (Cooling Distribution Unit) and liquid-cooled devices in the cabinet are deployed indoors, and the cooling capacity is replenished by air-cooled air-conditioning. The principle is shown in the following figure.

Liquid cooling technology benefits from the higher specific heat capacity of liquid than gas and higher heat dissipation efficiency. Liquid-cooled refrigeration uses liquid instead of traditional air to dissipate heat, and directly refrigerates high-heating devices such as CPU. The liquid cooling system only needs a small amount of energy-consuming elements such as water pumps, and the energy-saving effect is remarkable.

Summary

That's all for today. Mr. documentation, let's briefly summarize the four refrigeration technologies.

Refrigeration technology

Application scenario

Refrigeration efficiency

Deployment and operation and maintenance

Mechanical air-cooled refrigeration

Small data center

Lower

It's relatively simple

Chilled water refrigeration

Medium and large data center

High

It's complicated.

Indirect evaporation refrigeration

Micro-module / container data center

Higher

It's relatively simple

Liquid cooled refrigeration

Large data center

Extremely high

The basic demand for energy saving and consumption reduction in more complex data centers has not changed, and refrigeration technology has been moving in a greener direction. What the future refrigeration technology will look like, interested fans can leave a message to the document to talk about the development direction of refrigeration technology in your eyes.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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