Air Velocity through Piping
Air velocity through piping is the speed at which air flows within a specific section of piping and measure of how quickly the air molecules move through the pipe. Air velocity is an important parameter in various applications, particularly in ventilation, HVAC systems, pneumatic conveying, and industrial processes. The air velocity through piping depends on factors like the diameter of the pipe, the pressure difference across the pipe, the length of the pipe, and any obstructions or restrictions present in the system. It is closely related to the air flow rate, which is the volume or mass of air passing through the pipe per unit of time.
In some cases, air velocity can be controlled to ensure that certain criteria are met. For example, in HVAC systems, maintaining a certain air velocity can help ensure effective air distribution and comfort within a room. In pneumatic conveying systems, controlling air velocity is crucial to avoid material settling or blockages.
It's important to note that air velocity and air flow rate are related but distinct concepts. While air velocity focuses on the speed of air movement, air flow rate takes into account the quantity of air passing through a specific point over time. Calculating air velocity in a pipe involves considering factors such as the area crosssection of the pipe, the volumetric flow rate, and the density of the air. Engineers often use equations based on fluid dynamics principles to determine air velocity accurately. Additionally, specialized instruments like anemometers or pitot tubes can be used to directly measure air velocity in various applications.
Air Velocity through Piping formula 

\(\large{ v_a = \frac { Q_a }{ 60 \; \pi \; { \left( \frac {d}{24} \right) ^2 } } }\)  
Air Flow Rate through Piping  Solve for va\(\large{ v_a = \frac { Q_a }{ 60 \; \pi \; { \left( \frac {d}{24} \right) ^2 } } }\)
Air Flow Rate through Piping  Solve for Qa\(\large{ Q_a = 60 \; \pi \; v_a \; { \left( \frac {d}{24} \right) ^2 } }\)
Air Flow Rate through Piping  Solve for d\(\large{ d = 24 \; \sqrt{ \frac{ Qa }{ 60 \; \pi \; v_a } } }\)


Symbol  English  Metric 
\(\large{ v_a }\) = air velocity  \(\large{\frac{ft}{sec}}\)  \(\large{\frac{m}{s}}\) 
\(\large{ Q_a }\) = air flow rate  \(\large{\frac{ft^3}{sec}}\)  \(\large{\frac{m^3}{s}}\) 
\(\large{ \pi }\) = Pi  \(\large{3.141 592 653 ...}\)  
\(\large{ d }\) = pipe inside diameter  \(\large{ in }\)  \(\large{ mm }\) 
Tags: Velocity Equations Pipe Sizing Equations Air Equations