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.

PRINCIPLES OF THE 1NJECTOK. 93 The complets formula for jet pump efficiency is therefore— P W x l + (W + 1) ht> , .. . E = ---------------------. (xxxii.) J (tfx + Lj - t3) If the water is supplied to tlie pump from a point 011 a level with the latter, W has zero value, whilst if the water is supplied under a head, AV has a negative value, and must be subtracted from the reniainder of the niimerator. Application of Formula (xxxii.).—It is desired to calcu- late the mechanical efficiency of a jet pump; when the steam pressure is 95 Ibs. per square inch a-bsolute the incoming water is lifted through a height of 2 ft., the pressure within the pump is 5 Ibs. per square inch absolute. the delivery temperature is 175 deg. Fah., the delivery pressure 115 Ibs. per square inch absolute, and the Mat i o in pounds of water to steam passing- through tlie appliance 13 to 1. Then F _ (13 x 2) + (13 + 1) (115 x 2’3) 778(281+ 886 - 175)" = -0048, or 48 per cent. If the delivery temperature is neglected the efficiency is '42 per cent. Thö advantage possessed by the jet pump over other types of pump is its great simplicity. It is particularly well suited for dealing with Chemicals or liquids having oorrosive properties, as the nozzles can be suitably pro- t&cted"without altectimg the action of the apparatus.