How does a pitot tube measure air velocity?

A pitot tube measures air velocity by determining the pressure difference between static and dynamic pressures. This device consists of a small tube with two openings: one that faces the airflow, known as the dynamic or impact pressure port, and another that is positioned perpendicular to the airflow, known as the static pressure port.

When air flows into the pitot tube, it creates a dynamic pressure due to the motion of the air. The static pressure remains unaffected by the airflow direction and represents the pressure that would exist if there were no movement. By measuring both pressures, the pitot tube can calculate the velocity of the air using Bernoulli's equation, which relates pressure and velocity in a fluid. This relationship allows for an accurate assessment of the air speed, making it a crucial tool in HVAC systems for understanding air movement and distribution.

Other options do not align with the actual function of a pitot tube. For instance, calculating the weight of air and measuring temperature do not directly relate to how velocity is gauged. Similarly, using a rotating blade is characteristic of different speed measurement devices and does not apply to the methodology of a pitot tube.