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 INJECTOR. 87 From our theoretical calculations we therefore ascertain that 217*555 heat units are available for conversion into kinetic energy for carrying the combined condensed steam and water jet into the vessel being fed. From our previous ealoulations we find thai the delivery jet only represented the expenditure of 4'7 heat un/its, thus sliowing that 212*8 units must hiave been utilised otherwise than for the pur- pose for which they were availaible. The impact losses, ecldyinig motions, friction, etc., in the injector destroy a large portion of the kinetic energy of the jet and re-convert t)he same to heat energy, which. is absorbed by the> feed water. If the 212'8 units are divided betwe-en the 13 Ibs. of water the temperature of the latter will be raised fi’om 97 deg. Fah. to about 113'3. The heat units remaining in the steam at 5 Ibs. pre&swe per square inch äbsolute, after '17 (clryness fraction=‘83) thereof has been condensed, are as follows:-— Latent heat x -83 = 1001 x ‘83 = 831 units sensible heat =162 units Total............ 993 heat units. The excess of heat units in 1 Ib. of the steam over what is conitained in the delivery jet is thei’øfore: — 993 — 175 = 818 heat units. If the latter are divided between the 13 Ibs. of feed water, the temperature of the latter will be raised from 113-3 deg. Fali to 176’3 deg. Fah; or, sine© the actual delivery temperature is found to be 175 deg. Fah.., we may conclude tliat the 17 heat units remaining after tlie water has been raised to a temperature of 175 deg. Fah. represent the loss due to radiation from the injector and its conniecitions. Calculations in Conneotion with thb Injector. The most important calculation required to be made in conneotion with an injector is tliat for deteranining thø ratio by weiglit of water to steam passing through, the appliance.