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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.
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]
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]
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 ...
Due to the presence of vortices, large flow-turning and secondary flow result to form a complex flow field, and interaction between these effects increases endwall losses. In total loss, endwall losses form the fraction of secondary losses given by Gregory-Smith, et al., 1998. Hence secondary flow theory for small flow-turning fails.
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