About stable data center wetting

Malfunctions in data center equipment are not only due to deviations from the optimal temperature parameters. No less dangerous for the operation of electronic equipment violation of humidity. High humidity - a source of condensate that causes corrosion of conductors and oxidation of contacts, which in turn can cause failure of components of computer systems. On the other hand, the lack of moisture contributes to the destruction of varnish on electronic printed circuit boards, drying of insulation of power and switching wiring, as well as the formation of static electricity, which can lead to the failure of individual components.

A certain category of equipment in the data center is also sensitive to the purity of the surrounding air - the amount of dust it contains. In addition to the fact that accumulated dust slows down heat removal, it can lead to mechanical damage to the storage media when reading or writing data to a tape or disk.

Precision air conditioners have a humidification function: a small humidifier is built into the air conditioner itself. This is due to the fact that air conditioning leads to its drying in the premises of the data center. The reason for this is the condensation of moisture from the air when the heat transfer surface is cooled below the dew point.

As a rule, the device of humidifiers built into precision air conditioners is based on the isothermal principle, that is, they work like a classic boiler. The air is moistened by steam, which is formed when the water is heated by electrodes, through which an electric current is passed, sufficient for the water to boil quickly and start to evaporate. The controller of the precision conditioner collects information from humidity sensors installed in the room, and periodically turns on or off the humidifier. In such systems, water comes from ordinary water supply - special cleaning or water treatment is not required. In the humidification method based on boiling, the air is not heated.
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Another approach to humidification is based on the adiabatic principle, which can be implemented in different ways: either pressurized air is passed through a structure with a large wet surface (mats or special chambers), or pressurized water is sprayed in the air flow through the nozzles. Another method involves the use of an ultrasonic transducer, which creates a lot of small droplets above the surface of the water.

In addition, adiabatic humidifiers further cool the air. But if we consider the humidifier by itself, and not as an adiabatic cooling system, then the cooling effect from it is insignificant, as with the correct design of the data center the humidity is maintained quite accurately. Accordingly, the amount of external air in the data center is minimal, therefore, water also has to be added quite a bit.

Water consumption in both methods, both when using the classical method of evaporation and in the case of using adiabatic humidification, is small and does not have a fundamental effect on operating costs. But the energy savings in the method of adiabatic cooling is significant.

Evaporative systems, which are traditionally used for humidification and are based on the isothermal principle, are quite expensive to operate: when operating for four months, the classic evaporator with a power of 15 kW consumes electricity for 175 thousand rubles; thousand (depending on the size of PUE: 1.1–1.5). Therefore, the designers of the engineering equipment of the DataPro Tver data center decided to use the principle of adiabatic air humidification.
However, after examining the offers on the market in the segment of adiabatic humidification systems, DataPro experts came to the conclusion that the industrial system with finely dispersed water, along with its economical operation, also has a number of significant drawbacks. Primarily this includes poor scalability and low-level adaptability of such systems. In addition, long delivery times and commissioning of this system may be critical (launch dates are more than one year from the date of the contract). At the same time, the risk of possible damage to adiabatic systems on water mist is high enough, and the additional delivery of components lasts at least 3-4 months. Finally, it is quite difficult to change the logic of the operation of automation of industrial humidification systems of adiabatic type.



In DataPro they took into account all the listed disadvantages and designed their own adiabatic humidification system for the DataPro Tver data center. It uses: pneumatic pumps with nozzles, a compressor with a compressed air line supplied to the pump, and a water reservoir, and a water line connected to the pump. The effect is achieved with spray nozzles. In this solution, there are no high-pressure lines: purified water is supplied to the evaporator, which is driven to the nozzles with air under pressure of 3 atmospheres.
In Russia, this is one of the first implementations of such solutions.

Expert comment
Mikhail Balkarov, Emerson Network Power technical expert
Using a separate dampening system for large data center projects is welcome. This does not affect the stability of maintaining the specified moisture content parameters. At the same time, the system turns out to be simpler, cheaper and maintainable compared to traditional humidifiers built into air conditioners.

Adiabatic cooling is realized either by spraying water in the air flow through the nozzles; either by passing air through a special mat wetted with water; or by creating small droplets above the water surface due to the ultrasonic emitter. In any case, the power consumption is extremely small compared to other methods of humidification.

The disadvantages of using injectors and ultrasound include the need to fulfill the requirement of pre-cleaning water to avoid damage to the system. In addition, all remaining impurities immediately enter the air in the form of extremely fine dust.

Unfortunately, any solutions besides pluses always have minuses. For example, wetted mats and chambers are more cumbersome, in addition, measures will be required to combat pathogenic bacteria, including very dangerous ones - legionella.