. The steam-engine and other heat-motors . are InchPi- By EquationGiven By NapiersFormula. section ofOrifice. . . . 147014951490 * Table from Thomass Steam-turbines (Wiley). If dry saturated steam at pounds absolute flows throughan orifice whose cross-sectional area is .0355 square inch, againsta back pressure of pounds absolute, what will be thevelocity of discharge per second, volume and weight dischargedper second? Draw the entropy diagram, Fig. 119. Then the area TiT2s2mi V2represents H2-Hx in the formula — = 7
. The steam-engine and other heat-motors . are InchPi- By EquationGiven By NapiersFormula. section ofOrifice. . . . 147014951490 * Table from Thomass Steam-turbines (Wiley). If dry saturated steam at pounds absolute flows throughan orifice whose cross-sectional area is .0355 square inch, againsta back pressure of pounds absolute, what will be thevelocity of discharge per second, volume and weight dischargedper second? Draw the entropy diagram, Fig. 119. Then the area TiT2s2mi V2represents H2-Hx in the formula — = 778(H2-Hi). We may obtain that area by either exact or approximatemethods If TXT2 is assumed to be a straight line, the area of thetrapezoid TiT2s2mx is= (T2-T1)B, where 2L, , 2fo-fc) B= T2s2 + Tlmi 2e2e2+eie2 T7 2 TV Tt + T7 218 THE STEAM-ENGINE AND OTHER HEAT-MOTORS. (If the initial steam were wet, the area 772x2m37T1 would be thearea.) .. #2-#i = (809-768) [809 809+768 j72 = = 1500 feet per second. +331Jri?U«. Fig. 119. The more exact method would give 1470 feet per second. Ifthe steam expands adiabatically, its quality is Tint or eie3=r 1-5731 ENTROPY. 219 At pounds the volume per pound weight of dry steamis cubic feet. The volume per pound of wet steam = cubic feet. The volume discharged = area orifice Xvelocity. .0355X1470 — = . 362The weight discharged = ^—p = .0637 pound. Ex. 92. If steam of an initial absolute pressure of poundsflows through an orifice whose cross-sectional area is .0355 squareinch, against a back pressure of 67 pounds absolute, find the velocityof discharge and volume and weight of steam discharged per second. Condensation or Expansion at Constant Volume.—Fig. 120 illus-trates a series of events similar to those given in the example on Jb
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