Regarding the issue of fan static pressure
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The total pressure of the fan = total pressure at the outlet – total pressure at the inlet; this is easy to understand. But here’s the problem: in the fan manual, the static pressure of a fan is defined as the total pressure of the fan minus the dynamic pressure at the fan outlet, or it equals the static pressure at the fan outlet minus the static pressure at the inlet minus the dynamic pressure at the inlet, or it equals the outlet static pressure minus the total inlet pressure. Why isn’t the fan’s static pressure simply defined as the outlet static pressure minus the inlet static pressure? I hope fellow travelers will kindly share their insights!
This post was last edited by sifangok on 2017-5-11 at 18:10. In practice, the total inlet pressure generally remains constant; under such conditions, there is a linear relationship between the fan’s static pressure and the outlet static pressure. At the same volume and pressure, the higher the fan’s static pressure, the higher the outlet static pressure, allowing the air to be transported over a greater distance. The static pressure of a fan is defined as the total pressure of the fan minus its dynamic pressure. In fact, static pressure is the absolute pressure at a certain point in an airflow or in a gas-filled space. Stagnation pressure acts in all directions within a gas, independent of velocity, and is a measure of the potential energy in the gas. The above is copied over; in my opinion, this refers to the (maximum head) of the fan
Dude, at first I thought that \"fan static pressure = fan total pressure minus fan dynamic pressure,\" but the fan manual actually specifies total pressure minus outlet dynamic pressure, without mentioning inlet dynamic pressure. This is also something I haven’t understood.
It clearly involves inlet dynamic pressure; isn’t the inlet total pressure equal to the inlet dynamic pressure plus the inlet static pressure?
The \"Fan Manual\" states that the static pressure of a fan equals the total pressure of the fan minus the dynamic pressure at the fan’s outlet; the dynamic pressure at the inlet is not taken into account. Could it be a typo?
I think this statement is conditional, referring to the case where the inlet faces the atmosphere directly. Since the static pressure at the inlet remains constant and the dynamic pressure is zero, it can be said that the static pressure of the fan equals the total pressure minus the dynamic pressure. For fans, I believe it is possible to consider the head in the same way as with centrifugal pumps, that is, the pressure difference between the fan’s inlet and outlet, regardless of whether it is static pressure or dynamic pressure.
This post was last edited by RichardChan on 2020-6-28 07:06. Assume that the inlet area of the fan is 1 and the outlet area is 2. The dynamic pressure of the fan refers to the dynamic pressure Pd2 of the gas at the fan’s outlet area. The static pressure of a fan refers to the difference between the fan’s total pressure and its dynamic pressure. The fan’s total pressure is given by: (Outlet dynamic pressure Pd2 + Outlet static pressure Ps2) – (Inlet dynamic pressure Pd1 + Inlet static pressure Ps1). Therefore, the fan’s static pressure = Fan’s total pressure – Outlet dynamic pressure = Outlet static pressure Ps2 – (Inlet dynamic pressure Pd1 + Inlet static pressure Ps1)