Page:Model steam turbines; how to design and build them (IA modelsteamturbin00harrrich).pdf/24

20 at a constant level, and let it be provided with a discharge pipe terminating in a nozzle as shown. Suppose the relation between the height H and the area of the nozzle is such that one pound of water per second is discharged; each pound of water in falling from the tank to the nozzle does 1 × H foot pounds of work, this work is expended in giving velocity to the jet as it leaves the nozzle. Now the kinetic energy of the jet is, as has been

Fig. 9.

proved, $Wv²/2g$ foot pounds, or since W=1, $v²/2g$ is equal to the 1 × H foot pounds of work done in falling from the tank. Assuming no losses by friction in piping or nozzle, then

1 × H or H (foot pounds) = $v²/2g$(foot pounds) and therefore v²=2g (H foot pounds), or the velocity acquired v = √$\overline{2g × the work done in falling through H feet (5)}$

In exactly the same way we may calculate the velocity of steam in falling from an initial pressure p to final pressure p₂. The steam does not work on