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How to Increase Duct Pressure Through Aerodynamics

The flow of air through a duct can be manipulated by the geometry of the ductwork. Although aerodynamics is often thought of as the flow of air over or around a solid body such as a car or airplane, the same theories can be applied to the design of an air duct. For instance, air will flow differently if pushed through a sharp, square-edged corner, compared to a long radius smooth elbow. Another example is changing the sizes of a duct. Pressure can be increased with an increase in velocity. And velocity can be increased with smaller duct sizes. Total pressure is equal to static pressure plus velocity pressure. As velocity is increased, so is the total pressure.

Things You'll Need

Pen
Paper
Calculator

Instructions

- 1
  Determine the normal air pressure -- or static pressure-- and velocity in a duct. The pressure is measured in pounds per square inch (psi) and the velocity is measured in feet per second (fps). For instance, a common air duct could have a static pressure of 10 psi and a velocity of 50 fps.
- 2
  Determine the standard duct size and amount of size reduction. For instance, assume that a square duct is 24-square-inches and a reduction down to a 12-square-inch duct.
- 3
  Determine the increase in velocity from the 24-inch duct down to the 12-inch duct. This will double the velocity from 50 fps to 100 fps.
- 4
  Determine the velocity pressure increase in the duct. This velocity pressure is measured by the ratio of the increase in velocity. Therefore, doubling the velocity will double the velocity pressure and the new pressure will be 20 psi. This was achieved through a change in the aerodynamic nature of the duct.

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