Problems with the outlet pressure of the fan
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Today, I saw the outlet pressure of an air blower specified as follows: static pressure of 0.28, dynamic pressure of 0.22, with the unit being kPag. Why are dynamic pressure and static pressure indicated at the fan outlet? I understand that the fan draws air from the atmosphere; according to Bernoulli’s equation, the flow velocity of the gas at the inlet is 0, but there is a certain flow velocity at the outlet, so the dynamic pressure at the outlet also increases. However, between the fan outlet and the destination where the air is delivered, using Bernoulli’s equation, the dynamic pressure in this section should be able to cancel each other out; thus, during the air delivery process, it is still the static pressure at the outlet that plays a major role. The reason for specifying that the fan outlet consists of dynamic pressure and static pressure is mainly to calculate the fan power. I wonder if my understanding is correct? I’d like to ask everyone. . .
My understanding is that static pressure closes the outlet, creating a pressure buildup, while dynamic pressure is the pressure that exists when the outlet is not closed
That’s not what it means. Or conversely, how can one select a fan based on the length of the fan’s outlet duct?
Since there is a certain flow velocity at the fan outlet, it is necessary to take into account the impact of dynamic pressure on the total wind pressure; generally, the fan’s wind pressure represents the total pressure, which includes both dynamic pressure and static pressure； And the flow velocity at the pump outlet is low, so only the static pressure energy is generally considered ；
{:3_46:} Static pressure occurs when the outlet valve is fully closed, while dynamic pressure occurs when it is fully open. These are parameters that do not take into account the pressure drop in your outlet pipeline. I’m not sure if this is correct; you can check on Baidu
This question can be understood by referring to textbooks on chemical engineering principles. When the pipe outlet is used as the reference interface, if it is chosen on the outside side, there is no kinetic energy but there are outlet losses; if it is chosen on the inside side, there is kinetic energy but no outlet losses. In any case, a kinetic energy term is present, so this term must be included