What is the difference between the downward air supply and the upper air supply of the precision air conditioner

What is the difference between the downward air supply and the upper air supply of the precision air conditioner

There are multiple air supply and return modes for precision air conditioners in the computer room, such as upper air supply, lower air supply, upper return air, and lower return air. Different air supply methods are selected for different computer room environment and equipment requirements to ensure the stability of the computer room For efficient operation, the air supply mode of the special air conditioner for the computer room includes upper air supply and lower air supply.

　　What is a precision air-conditioning system?

The bottom air is provided with holes on the floor, the floor is used as a static pressure box, and an air outlet is installed under the rack, so that the air-conditioned lower temperature gas flows from the bottom to the upper process to control the rack to take away the heat. The cold air of the precision air conditioner is discharged downwards, and the cold air is sent to the equipment in the computer room to achieve cooling, so as to ensure that the program-controlled machine works at a suitable ambient temperature.

　　What is an upper air supply precision air conditioner?

The upper air supply system is opposite to the lower air supply method. The air diffuser is installed on the top of the machine room, and the cold air is discharged from the air outlet to cool the machine room. This air supply method is first mixed with air and affects the cooling effect. It is generally suitable for use in Small computer rooms or computer rooms with small heat dissipation are generally treated as static pressure boxes above the ceiling. When some users need to connect the air duct, we hope that the air duct should not be too long, and the static pressure consumption should be less than 75Pa. Longer air ducts are really needed, so consider using a booster fan system to compensate.

　　The difference between the upper and lower air supply of precision air conditioning in the computer room

　　The advantages of the air supply method:

　　 (1) The bottom air supply method is to send low-temperature air directly from the bottom to the communication equipment, absorb the heat of the communication equipment, and return from the top of the computer room to the top of the air conditioning unit. The flow direction of the air conditioning wind is consistent with the air characteristics, and it is easy to obtain a good air conditioning effect.

　　 (2) The space under the floor is much larger than the area of the duct section, which forms a static pressure box, so the downward air supply is uniform and the temperature difference in the entire machine room area is small.

　　(3) Because the air supply is in the raised floor, the distance from the downwind is the same as that of the upper air supply, the required air pressure is low, and the air conditioning equipment and air noise are relatively low.

　　(4) From the professional point of view of air conditioning, the downward air supply method does not require air ducts and air outlets. For design and construction, it is relatively simple and convenient, and the placement of air conditioning equipment can be adjusted flexibly. Since the lower air supply conceals all kinds of pipelines required for communication technology and the professional pipelines of air conditioning in the raised floor, the communication room looks neat and beautiful. Only from the professional investment of air-conditioning, the investment will be lower than that of the upper air supply.

Disadvantages of under the air supply method:

(1) Because the raised floor is mainly used for arranging various communication pipelines for communication equipment, some construction units consider reducing the fire protection area and reducing the investment in the gas fire extinguishing system. The net height of the raised floor is less than 400 mm, generally in the early stage of the project. There are few communication equipments and pipelines, and the layout of the pipelines is also neat and orderly, which can ensure that there is enough space for air conditioning. With the continuous expansion of the project, there are more and more equipment pipelines, and the subsequent construction is also How to save trouble and do so, so that enough area required for the air supply of the air conditioner cannot be guaranteed, thereby affecting the effect of the air conditioner.

(2) The bottom air supply is formed by the raised floor forming a large air supply box, which makes the air-conditioning in the communication room even far and near, so the quality of the raised floor directly affects the air-conditioning effect, due to poor floor quality, or improper construction or management It will cause a short circuit of the air supply and fail to reach the communication equipment rack at the distance of z*, which makes the temperature difference in the area of ​​the computer room larger, and does not use the communication equipment to work normally. Therefore, the air-conditioning effect of the lower air supply is affected by the quality, construction, maintenance and management of the raised floor.

(3) Although the airtightness of the machine room is good, dust still enters the machine room, especially in the northwest and northern areas, where there is a lot of wind and sand, and there is a lot of dust. It is easy to hide dirt under the raised floor and it is difficult to clean up. As a result, dust accumulates in some parts. The air supply under the air conditioner will cause dust to enter the communication equipment with the wind, increasing equipment failure, and affecting the normal operation of the communication equipment in severe cases.

　　 (4) The humidification water supply pipe and the condensate water drainage pipe of the downward air supply air-conditioning method are all arranged in the raised floor. When a problem occurs, it is not easy to find, and it is easy to cause safety hazards. This is unfavorable for safe production.

　　The advantages of the air supply method:

(1) Because the communication equipment is wired up and there is no raised floor in the computer room, the humidification water supply pipe and the condensate drain pipe required by the air-conditioning unit are all arranged explicitly. Once there is water leakage, it can be quickly found, eliminated in time, and eliminated. Factors of insecurity in the computer room. (2) There is no raised floor in the machine room, so it is not easy to accumulate dust. Even if there is dust in the room, it is easy to clean and clean, so that the filter of the air conditioning unit can be used for a long time and reduce the workload of maintenance and management.

(3) For the program-controlled switch room, communication equipment is generally installed in phases and batches, and the air-conditioning equipment is also installed in batches synchronously with the communication equipment. The computer room on the communication cable is conducive to the humidification of the air-conditioning equipment, the water supply pipe and the condensate drainage. The expansion and construction of the pipe.

Disadvantages of upper air supply method:

　　 (1) The air-conditioning air supply method of the upper air supply is from the upper part of the computer room to the communication equipment, and after exchange with hot air, it returns to the air-conditioning unit from the lower part of the computer room. The airflow organization of the air supply in the computer room contradicts the characteristics of the air flow, which makes the temperature in the lower part of the room high, which is not conducive to the operation of communication equipment.

　　 (2) According to the size of the computer room and the length of the air supply distance of the air conditioning unit, the specific form of air supply on the air conditioner is different. When the air supply distance is short, the air outlet of the muffler air supply cap can be used to directly send the air to the machine room. The airflow organization in the machine room is the upper side air supply and the lower side return air mode. When the air supply distance is long, it is necessary to set up the air supply duct in the upper part of the machine room, and send the air to the required part of the machine room through the air supply duct and air outlet of the air conditioner. In this way, the air supply duct and the air outlet need to be connected to the equipment. Coordination of similar wiring racks and lighting fixtures to avoid conflicts and bring a certain amount of work to design and construction.

(3) Since the upper air supply method is to directly blow the wind into the machine room or use the air supply pipe and air outlet to send the air to the machine room, the external residual pressure of the required air blower is higher than the lower air supply, and there is no air supply. In addition to the raised floor, the wind noise of the air supply itself is higher than that of the lower air supply. Therefore, the upper air supply type has higher noise than the lower air supply type for the air conditioning unit of the same specification.

(4) For the communication room with large depth, in order to evenly supply air to the air conditioner, air supply pipes need to be added. The upper part of the room is messy due to the arrangement of communication cable trays, air conditioning ducts, lighting fixtures, etc., and there is no downward air supply method. The machine room is neat and beautiful.

　　 Disadvantages of downward and upward air supply

In the past, special air conditioners for computer rooms often used two methods: bottom air supply or upper air supply. However, with the emergence of high-power servers, the above two air supply methods can no longer solve the heat dissipation problem of high-heat cabinets. The disadvantages include the following aspects :

(1) In order to ensure the effective convection of the cold energy sent by the air conditioner and the heat emitted by the equipment, and complete the cold and heat exchange, so that the electronic equipment can work within the specified ambient temperature and humidity, the air conditioner needs to be equipped with a larger power fan to ensure the large air volume of the air conditioner And high wind pressure, but this is very inefficient.

　　 (2) In most of the lower blower rooms, the cooling capacity sent by the air conditioner is often passed from bottom to top, and there are multiple servers in the 2.2-meter-high server cabinet. Although we hope that each layer of the horizontally placed server can be effectively cooled to ensure the safe and stable operation of the server, in fact, because the airflow composed of the air-conditioning air supply and the exhaust fan in the server is vertical, it is guaranteed that there is no compulsory closed air supply channel. Under the premise, it is difficult to ensure that the cooling capacity sent by the air conditioner can effectively enter the server cabinet. To ensure that the cooling capacity delivered by the air conditioner can reach 2.2 meters above the cabinet, the air speed delivered by the air conditioner is required to reach about 5 m/s. This fast wind speed requires a larger wind pressure in the transmission, and it is placed vertically. The fan in the server has low wind speed and pressure, so the cooling capacity sucked into the server is very limited. The cabinet with 2 kW heat can often meet the requirements, but for the cabinet with heat above 4 kW, the cooling capacity sucked in is far from Meet the requirements of hot and cold convection exchange, which leads to local overheating of the cabinet. If the air supply speed of the air conditioner is lower than 2.5 m/s, the cooling capacity delivered by the air conditioner will not be able to cool the server with a cabinet above 1.5 meters, and local overheating will occur.

　　 (3) Regardless of whether it is a downward or upward air supply method, it is difficult to make the air flow from the air conditioner distribute reasonably in the computer room according to the heat generated by the cabinet. This is the reason for the local overheating of the computer room after the appearance of high-heat cabinets.

　　Why precision air conditioners in the blower room are mostly used in the data center computer room

　　 Why are blower-type precision air conditioners used more in data center computer rooms? The reasonable arrangement of the airflow organization in the data center has a great effect on the cooling effect of the cabinet server. In the design process of the computer room, the precision air conditioner of the downward air supply mode is often used as the s* selection application.

In this layout, the cold air is first sent to the static pressure box under the floor, and enters the server cabinet through the air outlet floor to cool the IT equipment. The hot air discharged from the cabinet enters the computer room space and returns to the air conditioner through the computer room space. Return air through the ceiling space to the air conditioner for cooling.

　　 (1) Use of computer room: a computer room with raised floor and raised floor height ≥ 300.

　　 (2) Advantages: The lower part of the raised floor is a static pressure box as a whole. Relatively speaking, the air supply is relatively uniform during the air supply process. At the same time, due to the shielding effect of the floor, the noise of the air conditioner is relatively light during operation.

Lower blower-type precision air conditioners can ensure the normal operation of the equipment in the data center computer room. Therefore, the lower blower-type precision air conditioners are generally used for data center computer rooms. They are suitable for data centers with large heat dissipation and large computer room area. Choose the lower air supply method with better cooling effect, but the lower air supply requires high wiring in the computer room. If the upper wiring cannot be achieved, the wiring under the floor needs to be arranged reasonably to avoid blocking the air.