Pressure drop in fittings and curved pipes

So far, only the frictional pressure drop in straight lengths of pipe of circular cross-section has been discussed. The pressure drop in pipelines containing valves and fittings can be calculated from equation 2.13 but with fittings represented by the length of plain pipe that causes the same pressure drop. 

Equivalent lengths of various valves and fittings are readily available [Holland and Chapman (1966)] and a selection is given in Table 2.3. 

Fitting Number of equivalent pipe diameters LJdt Number of velocity heads K 

If the frictional losses were expressed as the head loss, hf= APf/pg, then the quantity 4fLJdi would multiply u2/2g. Thus 4/Le/d, is the total number of velocity heads lost. Consequently, an alternative presentation of frictional losses for fittings is in terms of the number of velocity heads K lost for each fitting. In this case, the total frictional pressure drop may be calculated as 

In equation 2.23, the first term on the right hand side gives the frictional pressure drop for the plain pipe of length L and the second term represents the total loss for all the fittings. Values of K are given in Table 2.3. 

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