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.

JOO THE STEAM INJECTOR. therefore —— x 70 A = 13'3________ A< 90 = 0'234 square inch = 0’0016 square foot. To calculate tlie delivery nozzle tliroat area, with any degree of ease we must make two assumptions. The first is as to the velocity of the delivery jet at the said throat, and the seeond is as to the density of the jet there. If we assume that the delivery jet velocity is 25 per cent greater than the velocity equivalent of the difference between the absolute delivery and overflow pres- sures, wliich amount errs on tlie small side, and take the density of the jet as that of hot water at the delivery temperature, which probably errs on the large side, we will obtain a fairly accurate result. This is the methocl adopted in the earlier calculation, -but it is again set out liere. Taking P,„ or the delivery pressure, as 95 Ibs. absolute, and Po, or the overflow pressure, as 15 Ibs. absolute, then : V(i = 1-25 72.7 x 2’3 (P(,-Po) = 1-25 764-4 x 2-3 (95 - 15) = 136 ft. per second. NT A W Now A,( = -------- p x V where A., = area in square feet of delivery nozzle throat, W = weight of water pissing in pounds per second, p = density of jet in pounds per cubic foot, and V — ve’ocity of jet in feet per second • ,, , . 4 x 14-3 therefore A(Z = ——-----------——------— 13*3 x 62‘4 x 136 = 0’0005067 square foot. A further inethod of approaching this, problem is to consider the momentum equation previously given, and which is as follows :