How to apply the functions of cooling, heating, humidification, and dehumidification of computer room air conditioning
1. Uninterrupted operation and year-round refrigeration
The heat dissipation of the equipment in the computer room is a steady-state heat source, and it operates continuously throughout the year. This requires an uninterrupted air-conditioning guarantee system. There are also high requirements for the power supply of the air-conditioning equipment. Not only is it necessary to have dual mains mutual investment, And for the air-conditioning system that protects important computer equipment, there should be a generator set as a backup power source. The long-term steady-state heat source causes the need for refrigeration even in winter, especially in the southern region. In the northern region, if cooling is still required in winter, when selecting an air conditioning unit, the condensing pressure of the unit and other related issues need to be considered. In addition, the proportion of outdoor cold air intake can be increased to achieve energy saving.
2. Large air volume, small enthalpy difference
The heat of the equipment is transferred to the computer room through conduction and radiation. The area with dense equipment generates concentrated heat. In order to make the temperature and humidity of each area in the computer room uniform, and to control it within the allowable base and fluctuation range, a larger The air volume takes away the residual heat. In addition, the latent heat in the computer room is small, and dehumidification is generally not required. When the air passes through the air conditioner evaporator, it does not need to drop below the zero temperature. Therefore, the temperature difference and enthalpy difference of the supply air are required to be small. Large air volume.
Three, sensible heat is large
Computer equipment such as hosts and peripherals, servers, switches, optical transceivers, and power supply equipment installed in the computer room, such as UPS power supplies, will dissipate heat into the computer room by means of heat transfer, convection, and radiation. This heat only causes the temperature in the computer room The rise is sensible heat. The heat dissipation of a server cabinet is several kilowatts to ten kilowatts per hour. If blade servers are installed, the heat dissipation will be higher. The heat dissipation of equipment in large and medium-sized computer rooms is about 400W/m2, and the data center with higher installed density may reach more than 600W/m2. The sensible heat ratio in the machine room can be as high as 95%.
Four, low latent heat
does not change the temperature in the computer room, but only changes the moisture content of the air in the computer room. This part of the heat is called latent heat. There is no humidity dissipating equipment in the computer room, and the latent heat mainly comes from the staff and outdoor air. The large and medium-sized computer room generally adopts the management mode of man-machine separation. The enclosure structure of the computer room is well sealed. The fresh air usually enters the man-machine room after temperature and humidity pretreatment. Therefore, the latent heat in the engine room is small.
5. The difference between computer room air conditioners and ordinary comfortable air conditioners
The computer room has strict requirements on temperature, humidity and cleanliness. Therefore, the design of the computer room special air conditioner is very different from the traditional comfort air conditioner, which is manifested in the following 5 aspects:
1. The traditional comfort air conditioner is mainly designed for personnel. The air supply is small, the air supply enthalpy difference is large, and the cooling and dehumidification are performed at the same time; while the sensible heat in the computer room accounts for more than 90% of the total heat, which includes the heating of the equipment itself, The amount of heat generated by lighting, the amount of heat conduction through walls, ceilings, windows, and the floor, as well as the radiant heat of sunlight, the penetration of wind and fresh air heat through gaps, etc. The amount of moisture generated by these heat generation is very small, so the use of comfortable air conditioning will inevitably cause the relative humidity in the computer room to be too low, which will cause the surface of the internal circuit components of the equipment to accumulate static electricity, which will cause discharge to damage the equipment and interfere with data transmission and storage. At the same time, as the cooling capacity (40% to 60%) is consumed in dehumidification, the cooling capacity of the actual cooling equipment is greatly reduced, which greatly increases the energy consumption.
The special air conditioner in the computer room adopts strict control of the evaporation pressure in the evaporator in the design, and increases the air supply so that the surface temperature of the evaporator is higher than the dew point temperature of the air without dehumidification. The cold energy generated is all used for cooling, which improves the work efficiency and reduces Moisture loss (large supply air volume, reduced supply air enthalpy difference).
2. Comfortable air conditioner has small air volume and low wind speed. It can only circulate locally in the air supply direction, and cannot form an overall air circulation in the computer room. The cooling of the computer room is uneven, resulting in a regional temperature difference in the computer room and low temperature in the air supply direction. The temperature in the area is high, and local heat accumulation of the heating equipment due to the different placement positions causes the equipment to overheat and damage.
The special air conditioner in the computer room has a large air supply volume and the number of air changes in the computer room is high (usually 30-60 times/hour). The entire computer room can form an overall air circulation, so that all equipment in the computer room can be cooled evenly.
3. The traditional comfort air conditioner, due to the small air supply volume and few air changes, the air in the computer room cannot be guaranteed to have a high enough flow rate to bring the dust back to the filter, and deposits inside the equipment in the computer room will cause the equipment itself. Adverse effects. Moreover, the filtering performance of general comfort air conditioning units is poor, which cannot meet the purification requirements of computers.
The special air conditioner used in the computer room has large air supply and good air circulation. At the same time, because of the special air filter, it can filter out the dust in the air in time and efficiently to maintain the cleanliness of the computer room.
4. Because most of the electronic equipment in the computer room runs continuously and has a long working time, the special air conditioner for the computer room is required to be designed to operate continuously throughout the year with a large load and maintain extremely high reliability. Comfortable air conditioners are difficult to meet the requirements, especially in winter, because the computer room has good airtightness and there are many heating devices, the air conditioning unit still needs to work normally. At this time, general comfort air conditioners are already difficult due to low outdoor condensing pressure In normal operation, the special air conditioner for the computer room can still ensure the normal operation of the refrigeration cycle through the controllable outdoor condenser.
5. The special air conditioner for the computer room is generally equipped with a special humidification system, a high-efficiency dehumidification system and an electric heating compensation system. Through the microprocessor, the temperature and humidity in the computer room can be accurately controlled based on the data fed back by the sensors, and it is comfortable Sexual air conditioners are generally not equipped with a humidification system and can only control temperature with low accuracy. Humidity is more difficult to control and cannot meet the needs of equipment in the computer room.
In summary, there are significant differences in product design between special air conditioners for computer rooms and comfort air conditioners. The two are designed for different purposes and cannot be used interchangeably. Special air conditioners must be used in the computer room. At present, many domestic industries, such as finance, post and telecommunications, television stations, petroleum exploration, printing, scientific research, electric power, etc., have been widely adopted, improving the reliability and economic efficiency of the computer, network, and communication systems in the computer room.
Six, the scope of application
Computer room precision air conditioners are widely used in high-precision environments such as computer rooms, program-controlled switch rooms, satellite mobile communication stations, large-scale medical equipment rooms, laboratories, testing rooms, and precision electronic instrument production workshops. Various indicators such as cleanliness and airflow distribution have high requirements, and they must be guaranteed by precision air-conditioning equipment in dedicated computer rooms that operate safely and reliably 24 hours a day, 365 days a year.