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# Three stages of centrifugal Fan selection

Oct 23, 2018

In the process of centrifugal fan selection, it is necessary to determine the gas flow rate, pressure and density, which are the three elements of the centrifugal fan selection process.

Density: if the density is not given, it is necessary to calculate or convert the density of the operating gas according to the operating environment of the fan, such as altitude, local atmospheric pressure, working temperature, gas density.

The first stage of selection:

Pressure: according to the given or calculated working condition density, the working pressure is converted into the fan standard state pressure.

Flow: if the system requires the mass flow of gas, it is necessary to convert the mass flow of gas into the volume flow in the standard state of the fan. If the system requires the volume flow of the gas, the volume flow in the standard state of the fan is the same as the volume flow in the working condition.

The second stage of selection:

The model of centrifugal fan determines its performance curve. The performance curve is divided into dimensionality curve and dimensionless curve. The dimensionless curve is the basis for determining whether or not to meet the requirements of the scene, while the dimensionless curve is the basis for describing the characteristics of the fan, the dimensionality represents the particularity, and the dimensionless dimension represents the universality. The commonly used dimensionless parameters are flow coefficient, pressure coefficient, internal efficiency and specific rotation number. One of the factors of flow coefficient and pressure coefficient can be used as the basis for calculating the fan machine number, the specific rotation number is the basis for selecting the fan model, and the internal efficiency is the basis for judging whether the model is an efficient fan or not.

The third stage of selection:

According to the known density, rotational speed, model and roundness of the coarse calculated fan machine number, using the drawing function of the software, the dimensional performance curve of the fan can be expressed. At the same time, the working point of the fan can be calibrated, and the dimensional performance table can also be listed. Calibrate the location of the operating point. Furthermore, the inner power of the fan can be calculated according to the actual working condition performance.http://www.jnblower.com/