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An axial fan is a type of fan that causes gas to flow through it in an axial direction, parallel to the shaft about which the blades rotate. The flow is axial at entry and exit. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan. Factors which determine the performance of the fan include the ...
Across the expansion fan, the flow accelerates (velocity increases) and the Mach number increases, while the static pressure, temperature and density decrease. Since the process is isentropic, the stagnation properties (e.g. the total pressure and total temperature) remain constant across the fan.
In irrotational flow, total pressure is the same on all streamlines and is therefore constant throughout the flow. [5] The simplified form of Bernoulli's equation can be summarised in the following memorable word equation: [6] [7] [8] static pressure + dynamic pressure = total pressure.
When a centrifugal fan is specified for a given CFM and static pressure at conditions other than standard, an air density correction factor must be applied to select the proper size fan to meet the new condition. Since 200 °F (93 °C) air weighs only 80% of 70 °F (21 °C) air, the centrifugal fan creates less pressure and requires less power.
Total pressure also known as stagnation pressure; sum of static pressure and dynamic pressure; pressure of the fluid if all the kinetic energy were to be converted into pressure isentropically Turbine rotor inlet temperature maximum cycle temperature, ie temperature at which work transfer takes place
q is the dynamic pressure in pascals (i.e., N/m 2, ρ (Greek letter rho) is the fluid mass density (e.g. in kg/m 3), and; u is the flow speed in m/s. It can be thought of as the fluid's kinetic energy per unit volume. For incompressible flow, the dynamic pressure of a fluid is the difference between its total pressure and static pressure.
In fluid dynamics, stagnation pressure, also referred to as total pressure, is what the pressure would be if all the kinetic energy of the fluid were to be converted into pressure in a reversable manner. [1]: § 3.2 ; it is defined as the sum of the free-stream static pressure and the free-stream dynamic pressure. [2]
The affinity laws are useful as they allow the prediction of the head discharge characteristic of a pump or fan from a known characteristic measured at a different speed or impeller diameter. The only requirement is that the two pumps or fans are dynamically similar, that is, the ratios of the fluid forced are the same.