Excess head loss

Kf is the excess head loss due to the pipe or pipe fitting (dimensionless) and u is the fluid velocity (length/time). 

For fluids flowing through pipes the excess head loss term Kt is given by... 

For pipe fittings, valves, and other flow obstructions the traditional method has been to use an equivalent pipe length Lequiv in Equation 4-30. The problem with this method is that the specified length is coupled to the friction factor. An improved approach is to use the 2-K method,s-6 which uses the actual flow path length in Equation 4-30 — equivalent lengths are not used — and provides a more detailed approach for pipe fittings, inlets, and outlets. The 2-K method defines the excess head loss in terms of two constants, the Reynolds number and the pipe internal diameter ... 

Kf is the excess head loss (dimensionless), V and are constants (dimensionless),... 

Determine the excess head loss terms for the pipe (using Equation 4-30), for the fittings (using Equation 4-38), and for any entrance and exit effects (using Equation 4-39). Sum the head loss terms, and compute the net frictional loss term using Equation 4-29. Use the velocity at point 2. 

K are the excess head loss terms, including pipe entrances and exits, pipe lengths, and fittings (unitless). 

The excess head loss terms 2 Kt are found using the 2-K method presented earlier in section 4-4. For most accidental discharges of gases the flow is fully developed turbulent flow. This means that for pipes the friction factor is independent of the Reynolds number and that for fittings Kf = and the solution is direct. 

Assume fully developed turbulent flow to determine the friction factor for the pipe and the excess head loss terms for the fittings and pipe entrances and exits. The Reynolds number can be calculated at the completion of the calculation to check this assumption. Sum the individual excess head loss terms to get 2 Kf. 

Table 4-4 Correlations1 for the Expansion Factor Yg, and the Sonic Pressure Drop Ratio (P1 - P2)/Pi, as a Function of the Excess Head Loss K,2...

The simplified procedure with a direct solution can also be used. The excess head loss resulting from the pipe length is given by Equation 4-30. The friction factor/has already been determined ... 

Excess Head Loss K Correlation for Fitting Caused by a Change in Pipe Size... 

Hooper developed a new technique called two-K method to predict the head loss in pipe fittings [49], He defined K, a dimensionless factor, as the excess head loss in a pipe fitting, expressed in velocity heads. It is a function of Reynolds number and of the exact geometry of the fitting as... 

Assume > 10,000. Then the excess head loss for the fluid entering the holeisi(Q= 0.5. 

The calculated results arc determined as follows. The Reynolds number is determined from the guessed velocity, the pipe diameter, the fluid density and viscosity. The friction factor is determined using Eq. (2.7). The Kf faaors for the elbows and valves are determined using Eq. (2.4). The Xf factors for the inlet and exit effects are determined using Eq. (2.6). The pipe Kf factor is found using Eq. (2.3). The excess head loss factors for the complete piping system are summed as shown. 

The required diameter of the pipeline is mainly determined by the pumping capacity of the dredger but may also be influenced by the type of material to be transported, the length of the pipeline, the number of branches, etc If the diameter of the pipeline is too small, friction as a result of high velocities may cause excessive head loss, while a too large diameter may result in deposition of fill material inside the pipeline. 

---