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.

94 THE STEAM INJECTOR. CHAPTER VIII. Nozzle Dimensions. The problem of determining the throat areas of the steam and delivery nozzles øf an injector from the result of tests is a difficult one, but has been approached in -various ways, all of which are subject to error owing to the impossibility of stating witli any degree of accuracy the nature and amounts of the various velocity and other losses. According to one proposed method a result is obtained by comparing the condition of the steam jet as it passes the steam nozzle throat witli that of the water j©t as it passes tlie delivery nozzle throat. In this case we require for our calcukations the initial steam pressure and dryness fraction, water head at inlet, water temperature and pressure, and the quantity of water received or delivered by the injector in a specified time. Witli thesø particulars we first proceed to determine the dryness fraction at the steam nozzle throat, the pressure there being *58 of the inlet pressure. This value is always abo ut *96, but can be calculated by foinmula (vii.) as follows • To We then proceed to determine the velocity of th© steam at the nozzle throat and also >as it leaves the steam nozzle. for the actual velocity imparted to the incoming feed water is that of the steam leaving the steam nozzle. These va lueis can be calculated from formula (vi.), namely: — x/2y J + Xx - t., — x.< L2).