What happens to the air pressure inside a duct when velocity pressure increases?

When the velocity pressure within a duct increases, it indicates that the speed of the air moving through the duct has risen. According to the principles of fluid dynamics and the relationship between different types of pressures in duct systems, an increase in velocity pressure generally leads to an increase in the static pressure.

Static pressure is the pressure exerted by the air on the walls of the duct when the air is not in motion. When velocity pressure increases—reflecting a higher airspeed—there is more dynamic pressure acting on the air particles. This change can compress the air molecules, leading to a higher static pressure as the air is forced to move through the duct system.

Thus, the increase in velocity pressure effectively elevates the static pressure within the duct system, reinforcing the idea that as air moves faster, its static pressure responds positively to the increase in kinetic energy of the moving air. This relationship is critical in HVAC design and performance, ensuring systems maintain proper pressure balances for efficient operation.