How is pressure drop calculated in a piping system?

In a piping system, pressure drop is a critical factor that can affect system efficiency and performance. The correct calculation, outlined in the first choice, is based on the Darcy-Weisbach equation, which is used to determine the pressure loss due to friction in a given length of pipe.

The formula provided states that pressure drop is proportional to the friction factor, the length of the pipe divided by the cross-sectional area, and a term involving the fluid's density and the square of its velocity. The inclusion of the square of the velocity is key since the pressure drop across a pipe increases with the velocity of the fluid.

In essence, the equation considers how friction affects flow through the system, allowing for an understanding of how much pressure will be lost as fluid moves through the pipe. The balancing of these factors provides a comprehensive view of how they interact in a dynamic system, which is essential for designing efficient HVAC systems.

The other choices present variations of the equation, but they do not adhere to the established principles of fluid mechanics. The inclusion of the terms and coefficients in the correct equation reflects a deeper understanding of how flow dynamics are evaluated in practical applications.