Energy-saving technology of data center air conditioning system - Indirect natural cooling of computer room air conditioner
Time of issue:2022-12-02
1. Principle of precision air conditioner for indirect natural cooling machine room
The indirect natural cooling system of computer room air conditioner is composed of indoor unit, outdoor dry cooler (or cooling tower) and water pump. The indoor unit is a natural cooling cold water coil added to the evaporator coil of the water-cooled unit. When the outdoor temperature is high, the compressor runs in refrigeration, the cooling water absorbs heat in the plate heat exchanger, and dissipates heat through the dry cooler (or cooling tower); when the outdoor temperature is relatively low, when the water temperature reaches a certain requirement, control the water valve , Let part or all of the cold water flow through the natural cooling cold water coil to cool part or all of the load in the room. Because the refrigerant cycle is independent of the free cooling water cycle, the system has a mixed operation mode, that is, while using free cooling, the compressor runs intermittently to ensure the cooling capacity requirement. This increases the outdoor temperature range using free cooling, resulting in greater energy savings.
2. Indirect natural cooling machine room precision air conditioning control
According to the outdoor temperature and load, the system automatically switches the mode of the air conditioner controller in the machine room. The higher the set indoor return air temperature, the longer the natural cooling time with outdoor fresh air. Taking the indoor return air temperature as 27°C as an example, When the outdoor temperature is lower than 24°C, the natural cooling can be started and the mixed mode operation can be entered. The operating mode of the system is as follows:
1) In compressor mode, when the outdoor temperature is higher than 24°C, the natural cooling water valve is closed, the condenser water valve is opened, and the unit operates in compressor mode to provide cooling capacity for the machine room. The cooling system consumes the most energy in this mode.
2) Mixed mode When the outdoor temperature is within the range of 13°C to 24°C, the unit operates in mixed mode. In this mode, the water valve of the natural cooling coil is opened, the water valve of the condenser is opened, the compressor works intermittently, and the cold water provided by the dry cooler continues to provide part of the cooling capacity for the machine room. Between 42 and 90%. Mixed mode has a larger percentage throughout the year to minimize compressor run time.
3) Natural cooling mode The outdoor temperature is lower than 12°C and the system can realize natural cooling. Compressor cycling does not work in this mode. The chilled water is produced by the dry cooler to provide cooling capacity for the computer room. At this time, the energy saving effect is the most significant, and the power consumption is only about 21%~37% of that in the compressor mode.
3. Advantages of precision air conditioning in indirect natural cooling machine room
The application of indirect natural cooling air-conditioning units in computer rooms has the following advantages:
1) Better environmental applicability: Since there is no fresh air cooling, the indirect natural cooling has lower requirements on the quality of outdoor air, and the scope of application is wider;
2) Significant energy saving effect: In the northern region, 40% of the cooling energy consumption can be saved throughout the year, and more than 12% of the cooling energy consumption can be saved in the Guangzhou area;
3) Installation and design are more flexible and convenient: water cooling is used for cooling, and the distance of pipelines is not limited. The dry cooler can be placed on the roof or on the ground, and the application is more convenient;
4) The solution is more reliable: each unit has its own compressor system, and the failure of a single unit does not affect the operation of other units;
5) Redundant configuration is more economical: the indoor unit and dry cooler can be configured with N+1 redundancy, which is cheaper than the 1+1 or N+1 configuration of the chiller system;
6) Reduced filter maintenance cost: no fresh air cooling, saving the maintenance cost of fresh air filter.
4. Indirect natural cooling machine room precision air conditioning application area
Indirect free cooling is suitable for most areas in China. Indirect free cooling requires less outdoor air and is suitable for more complex installation environments. In terms of application scale, the indirect natural cooling system of computer room air conditioners is suitable for data computer rooms of various sizes.