In differential pressure meters, increased velocity in a closed conduit results in which change in pressure?

• A. Increased pressure
• B. Reduced pressure
• C. No change
• D. Fluctuating pressure

Answer: (B)

When fluid speeds up in a closed conduit, its static pressure falls while its kinetic energy rises. This is Bernoulli’s principle in action. A differential pressure meter has taps upstream and at the constriction (throat). As velocity increases, the static pressure at the constriction drops relative to the upstream pressure, so the local pressure is reduced. That pressure drop is what the meter uses to infer flow, but the direct change in pressure at the constriction is a reduction. So the correct idea is that pressure decreases with increased velocity.