The Steam Injector
A theoretical and practical treatise on the design and operation of injectors and on the flow of fluids through and the design of nozzles.

86 THE STEAM INJECTOR. the steam will give up a certain amount of its heat energy, and a portion of the steam will condense. Using formuia (vil.) to calculate the dryness fraction x2 when xA is taken as unity, we get—- 601-6 = ‘83 approximately. That is to say, the steam contains ‘17 moisture when its expansion is completed. The total heat given up by the steam in expanding <%s aforesaid is therefore as follows, using- the symbols of equation (vi.): — ■ Heat units given up by steam = (ix + - t., — x2 L2) = (324 + 886 - 162 - -83 x 1001) = 217-2. Thus, tli© steaiiii supplies 217*2 heat units for use as the motive power in propelling the water jet into the boiler. The water jet provides a very small amount of the pro- pulsive force. The heat energy representer! by each 13 Ibs. of the water entering the injector where the pressure is 5 Ibs. per square inch absolute, after beting lifted 2 ft., is obtained as follows, taking 1 Ib. pressure as equal to a fluid head of 2‘32 ft., and ramembering that the unbalanced pressure on the water tending to drive it into the injector is 10 Ibs. : — tt , Mass in pounds Velocitv2 Heat energy = =—n-------.------- x --------— Joule s equivalent 2 g W — — x (head equivalent in feet of 10 Ibs. pressure — 2) x (10 x 2-32 - 2) = -355 B. T. Units. 13