In many production industries, the efficiency of centrifugal fans often directly affects production energy consumption. At present, many companies include the improvement of centrifugal fan efficiency when formulating energy-saving plans, and the specific efficiency calculation has become a major premise. How to calculate fan efficiency to be more accurate? How to improve the efficiency of centrifugal fans?
Efficiency calculation formula of centrifugal fan
The efficiency of the centrifugal fan refers to the ratio of the active power of the conveyed medium to the motor power, and its calculation formula is as follows:
In the formula:
η is the efficiency of centrifugal fan (%);
k is the compression factor, usually 0.99;
P is the pressure of the centrifugal fan (Pa);
Q is the flow rate of the centrifugal fan (m³/s);
N is the input power of the motor (kW);
The pressure of the centrifugal fan is mainly divided into full pressure and static pressure. When the centrifugal fan pressure (Pa) in the above formula is full pressure, the calculated efficiency is the total pressure efficiency, and when it is static pressure, the calculated efficiency is the static pressure efficiency. Although the main parameter introduced by many manufacturers to users is static pressure, in actual use, it is more reasonable to express the efficiency of the centrifugal fan by the total pressure efficiency.
Generally, the efficiency of a centrifugal fan directly represents its energy saving (energy consumption) situation, so a centrifugal fan with higher efficiency can provide a better energy-saving solution for enterprises. The method of improving the efficiency of centrifugal fans in enterprises is mainly carried out from two aspects: one is to choose centrifugal fans with more energy saving and higher efficiency; the other is to transform existing ventilation systems and centrifugal fans.
How to improve the efficiency of centrifugal fans
1. Select a new centrifugal fan
For enterprises, it is undoubtedly a more direct and effective way to choose a new centrifugal fan, but most of the centrifugal fan manufacturers on the market still use relatively backward technologies, and a large number of centrifugal fans produced by these manufacturers exist in the fan market. Therefore, it is necessary to choose more advanced and efficient fans. For example, the centrifugal fans we design and produce with ternary flow fan technology have higher full-pressure efficiency and lower failures.
In addition, in order to ensure that the centrifugal fan meets the needs of energy saving, the fan parameters must be selected reasonably. At present, the performance of centrifugal fans is relatively accurate, so when selecting parameters, it is not necessary to leave too much margin, and it is sufficient to comply with the principle of moderation.
2. Retrofit the existing ventilation system
The ventilation system is also an important factor that directly affects the efficiency of the centrifugal fan, so the centrifugal fan can be fully utilized by optimizing the existing system. For example, optimizing the pipeline system to avoid sharp turns or sharp changes in the flow area, or setting guide vanes at the elbow of the pipeline according to the situation to reduce the loss of airflow; another example can make the pipeline at the inlet and outlet of the centrifugal fan long enough Straight pipe section, or use rectifier grille in the pipeline to reduce the turbulence of the airflow in the inlet and outlet pipelines, thereby improving the efficiency of the centrifugal fan.
3. Retrofit existing centrifugal fans
For the existing centrifugal fan, its efficiency can be actually tested, and then modified in the following ways to achieve the purpose of saving energy:
(1) For the centrifugal fan whose actual operating point deviates far from the design point, variable frequency drive can be added, the transformation is relatively simple, and the energy saving effect is very obvious.
(2) For the fan equipment with backward technology, it is possible to consider replacing the whole machine. During the transformation, the inlet and outlet air ducts can basically continue to be used, and the basic changes can be applied to the new centrifugal fan.
(3) For centrifugal fans whose actual operating working point deviates little from the design point, the rotor can be replaced or the blades can be replaced to improve its efficiency.
(4) In the case of large losses in the centrifugal fan system, it can be considered to increase the guide vanes in the air ducts and elbows to reduce the airflow loss, so as to achieve the purpose of energy saving.
How is power independent of the density of the medium?