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The head loss Δh (or h f) expresses the pressure loss due to friction in terms of the equivalent height of a column of the working fluid, so the pressure drop is =, where: Δh = The head loss due to pipe friction over the given length of pipe (SI units: m); [b]
The equation for head loss in pipes, also referred to as slope, S, expressed in "feet per foot of length" vs. in 'psi per foot of length' as described above, with the inside pipe diameter, d, being entered in feet vs. inches, and the flow rate, Q, being entered in cubic feet per second, cfs, vs. gallons per minute, gpm, appears very similar.
This dissipation, called head loss, is divided into two main categories, "major losses" associated with energy loss per length of pipe, and "minor losses" associated with bends, fittings, valves, etc. The most common equation used to calculate major head losses is the Darcy–Weisbach equation.
The friction loss is customarily given as pressure loss for a given duct length, Δp / L, in units of (US) inches of water for 100 feet or (SI) kg / m 2 / s 2. For specific choices of duct material, and assuming air at standard temperature and pressure (STP), standard charts can be used to calculate the expected friction loss.
Before being able to use the minor head losses in an equation, the losses in the system due to friction must also be calculated. Equation for friction losses: = [5] [3] [1] = Frictional head loss = Downstream velocity
Pressure head is the difference in pressure between the suction point and the discharge point, expressed as an equivalent height of fluid. Velocity head represents the kinetic energy of the fluid due to its bulk motion. Friction loss (or head loss) represents energy lost to friction as fluid flows through the pipe.
Once the friction factors of the pipes are obtained (or calculated from pipe friction laws such as the Darcy-Weisbach equation), we can consider how to calculate the flow rates and head losses on the network. Generally the head losses (potential differences) at each node are neglected, and a solution is sought for the steady-state flows on the ...
ΔE is the fluid's mechanical energy loss, ξ is an empirical loss coefficient, which is dimensionless and has a value between zero and one, 0 ≤ ξ ≤ 1, ρ is the fluid density, v 1 and v 2 are the mean flow velocities before and after the expansion. In case of an abrupt and wide expansion, the loss coefficient is equal to one. [1]