In building ventilation systems, centrifugal fans are often used as fans in many cases. Generally, in order to ensure good ventilation in buildings, centrifugal fans that can be long-term, stable and have higher efficiency are often selected, but the working environment of fans is restricted. Because of its performance, it is necessary to pay more attention to the working environment requirements of centrifugal fans when designing and selecting models.
1) Working environment requirements and selection parameters of centrifugal fans
1. Environmental requirements
Usually when designing a building ventilation system, the relevant parameters of the centrifugal fan are required to better adapt to its working environment. There are two main parameters related to the working environment of the centrifugal fan: the upper limit of ambient temperature (tR) and the protection level (IPXX). ). The upper limit of ambient temperature (tR) requires that the centrifugal fan must work below this temperature, otherwise the motor may be burned; the protection level (IPXX) requires that the fan seal can meet the sand and dust environment, otherwise the surrounding environment is too sandy, which will increase the dust on the fan. The wear and tear of the fan will reduce the service life of the fan, so the corresponding filter system should be designed to reduce damage.
2. Environmental selection parameters
(1) Upper limit of ambient temperature (tR): refers to the temperature of the gas medium flowing through the fan impeller and motor when the fan is working normally.
(2) Protection class (IPXX): refers to the dustproof and waterproof characteristics of electrical appliances, which consists of two digits, the former number is the dustproof level, and the latter number is the waterproof level.
2) The influence of environmental parameters on fan performance
1. The influence of ambient temperature
In a stable working state, the heat generated by the fan motor and the heat taken away by the gas will reach a balance. At this time, the temperature difference between the temperature of the motor and the ambient temperature reaches a stable value, which is called the temperature of the motor in this working state. Lift. In most cases, for the same motor, the temperature rise is related to its power. The higher the power, the higher the temperature rise. Since the insulating material used in the motor has a certain heat-resistant temperature, when the temperature does not exceed this temperature, the insulating material can ensure good insulation, but when the temperature exceeds the insulation level of the insulating material, the insulation will fail, and the coil may be short-circuited. Danger of burnout. Therefore, when the fan runs at the upper limit of its power, the temperature rise of the motor reaches the upper limit. If the temperature of the gas medium flowing through the motor is too high at this time, it is very likely that the temperature inside the motor will exceed the resistance of the insulating material. Due to the limit, it will lead to insulation failure, or cause the insulation material to accelerate aging and reduce the service life.
2. Influence of protection level
The protection level of most centrifugal fans is IP54, and the protection level of a small number of fans to enhance the heat dissipation function is only IP20. Under the protection level of IP54, the fan can isolate most dust and rain splashing, but it is not completely dustproof and waterproof. When used in some areas with severe wind and sand, if the ventilation system does not take adequate measures to prevent wind and sand, the dust may enter the inside of the motor. After a large amount of dust accumulates inside the motor, it will adhere to the bearing surface in the motor and enter the bearing along the bearing gap. Subsequently, the lubricating grease in the bearing will gradually reduce the lubricating performance due to the infiltration of dust, causing it to completely lose its lubricating effect, and the bearing will be stuck or deflected, causing the motor to be scrapped.
