Choice of precision air conditioner in data center computer room

There are many types of air conditioning refrigeration systems in the computer room. Different refrigeration systems can be selected according to the characteristics of the project. The cooling system of the air conditioning unit for the computer room is mainly cooled by air-cooled, water-cooled or glycol water-cooled, chilled water and double cold source systems. In general, the contents to be referred to when selecting a cold source form include: system investment, system performance, operation and maintenance costs, and location climate conditions.

(1) Air-cooled system 1. Composition and working principle of air-cooled unit The air-cooled direct evaporation system uses refrigerant as a heat transfer medium. The refrigeration system in the unit consists of refrigeration pipes such as evaporator coils, compressors, and condensers. The indoor air circulates through the internal air duct of the unit. The remote air-cooled condenser is connected to the indoor unit, and the entire refrigeration cycle is in a closed system to absorb the heat load in the room and discharge it into the atmosphere.

2. Application characteristics of air-cooled unit The application of air-cooled unit in the data center computer room is extensive, and it has the following characteristics.

advantage:

(1) Direct evaporative refrigeration cycle with no chilled water and cooling water system.

(2) Each unit has its own compressor, which can realize N+1 backup mode in each machine room.

(3) The installation content is relatively simple.

(4) The outdoor unit is installed and dispersed, and there is no need to consider too much load bearing problems of the outdoor unit.

(5) Routine maintenance is relatively simple and does not require consideration of the water system.

Disadvantages:

(1) For large data centers, each unit and compressor refrigeration system requires a set of cooling copper pipe connections, which has a huge amount of engineering.

(2) The distance between indoor unit and outdoor unit is limited, and the efficiency will decrease significantly when the equivalent length is greater than 50m.

(3) In large data centers, the number of outdoor units is relatively large due to the large number of outdoor units.

(2) Water-cooled or glycol-water-cooled system 1. Composition and working principle of water-cooled unit The internal structure of the water-cooled or glycol-cooled system is the same as that of the air-cooled unit, and the indoor air circulates through the evaporator coil. Unlike the air-cooled type, the water-cooled unit is equipped with a plate condenser inside, which will convert the heat between the room heat and the glycol solution. The liquid in the condenser acts as a secondary heat transfer medium and is pumped into a remotely mounted air-cooled dry cooler or cooling tower where the heat is discharged to the atmosphere. Water cooling system room dedicated air conditioning unit Each unit has its own refrigeration cycle system, and is equipped with a separate water-cooled condenser. The condenser is placed inside the indoor unit. The cooling water of all units can be made into a cooling water circulation system, and the circulating power is provided by the water pump. The outdoor cooling water can be used in two ways: an open cooling water tower and a closed dry cooling unit. The air conditioning in the computer room is required to run continuously throughout the year. The closed dry cooler is more energy-intensive and should not be used; the cooling method of the cooling tower is usually adopted. In terms of energy saving, some dedicated air conditioning units are connected in parallel to a natural cooling coil on the evaporator of a water-cooled or glycol cooling system. At lower outdoor ambient temperatures, the valve is precisely controlled by the central controller, and the natural cooling coil will absorb all of the heat transfer in the chamber. During the season, the ambient temperature will drop below the temperature required by the machine room. The natural cooling coil will provide pre-refrigeration to reduce compressor run time. The compressor typically requires only 80% of the input power, which can result in significant cost savings.

2. Application characteristics of water-cooled unit:

(1) The condenser and evaporator of each unit are inside the indoor unit, and the refrigeration cycle system is completed inside the unit, and the cooling efficiency is higher than that of the air-cooled unit.

(2) There is no need to connect copper pipes between indoor and outdoor units. Only one set of cooling water pipes can connect all the units together. In the large data center system, the engineering quantity can be relatively reduced, and there is no indoor or outdoor unit distance. limit.

(3) Several sets of large outdoor dry coolers can be used for N+1 backup work, and the area of ​​medium and large data centers is relatively small.

(4) It is convenient to expand the capacity, and the interface is reserved during the initial design. It is not necessary to find the indoor and outdoor unit channels when it needs to be expanded after being put into use.

(5) The water circulation pipeline does not need too thick heat preservation treatment to save channel space.

Disadvantages:

(1) The data center has a water circulation system inside, and it is necessary to set up a leak detection system and protective measures.

(2) The construction project is relatively complicated and needs to be completed by the engineering team with the pressure pipeline construction process.

(3) The daily maintenance work is more complicated than the air-cooled type, the water quality requirements are relatively high, the failure rate and maintenance cost are high, and it is easy to form a single point failure, but it is simpler than the chilled water type.

(4) Limited energy-saving effect, high energy consumption in small and medium-sized computer rooms, low-energy consumption in air-cooled air conditioners in large computer rooms, but high energy consumption compared with chilled waters, and low operating and maintenance costs, so water-cooled air conditioners are generally used. There are fewer rooms.

(III) Chilled water system When a central air conditioning chilled water system or a separate air-cooled chiller unit is used as the heat exchange mode, the indoor air can directly transfer the heat load to the chilled water system through the chilled water coil. Under the control of the central controller of the dedicated air conditioning unit, the water flow is regulated by a two-way or three-way cooling water valve to accurately maintain the temperature in the equipment room. When using a separate air-cooled chiller to provide a cold source, it is advisable to have multiple N+1 backup methods to improve the operational guarantee capability of the entire system. To improve the safety and backup capacity of the air conditioning unit, two separate cooling coils and control valves can be installed in the unit to handle chilled water from two separate systems. The central air-conditioning chilled water system can be used as the basic chilled water source, and the separate air-cooled chiller unit is used as the secondary chilled water source, which is especially suitable for the case where the central air-conditioning chilled water system is no longer used on weekends or late at night.

advantage:

(1) The air-cooled chiller is centrally cooled, the cooling efficiency is high, and the operating cost is low.

(2) There is no need to connect the copper pipes of the indoor unit and the outdoor unit, and only one set of cooling water pipes is needed to connect all the units together.

(3) In large data center systems, the amount of engineering can be relatively reduced.

(4) There is no limit on the distance between indoor unit and outdoor unit.

(5) Several sets of chillers can be used for N+1 backup work, and the floor space is relatively small.

(6) The price of the indoor unit is very cheap and the overall cost is low.

Disadvantages:

(1) The data center has a water circulation system inside, and it is necessary to set up a leak detection system and protective measures.

(2) The construction project is relatively complicated and needs to be completed by the engineering team with the qualification of pressure pipeline construction.

(3) The routine maintenance work is complicated and requires maintenance personnel in the chiller.

(4) Double cold source system The above three basic cooling methods can form different types of dual cold source systems, such as air-cooled + chilled water system, water-cooled + chilled water system.

1. Air-cooled + chilled water system The air-cooled + chilled water system consists of cooling coils of air-cooled and chilled water systems, respectively, operated by a central controller control system, and the air-cooled system is used as a backup system for the chilled water system. The security of the computer room and additional backups, and vice versa.

2. Water-cooled + chilled water system The water-cooled + chilled water system consists of two coils of water-cooled and chilled water systems, which enable the two systems to back up each other.

3, the application characteristics of the dual cold source system advantages:

(1) It has strong adaptability and flexible cooling method.

(2) The dual systems are backups of each other with high security and reliability.

(3) The energy-saving mode of the unit can be fully utilized.

Disadvantages:

(1) The initial investment is large.

(2) There are many pipelines, which take up a lot of space and bring trouble to the installation.

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