I UK TAHU.s AM) MAORAMS 



In adiabatic expansion tlu entropy remains constant; hence the 

 is given action of the line i 1.637 * ln ln * saturation curve, 



pressure d l.\ thU |x.int is 68 Ib. per sq. 



Example 3. Steam in the - ami . initial state as in Examples i and 2 nrpands 

 adiabatically to a pressure of 2.5 in. of mercury. Find the volume, beat con- 



iergy, and qualit> in the final stats). 



The entmp) in the initial state is 1.637; hence find the interaction of the 



h the curve p - 2.5 in. of Hg. This point gives the values 



x - 0.822, t - 925 B.t.u. From Table I, *" for 2.5 in. of Hg is 274.7 cu. ft-. 



hence (he \<>lunu , : the mixture \viih quality of O.822 i* 274.7 X O.822 - 225.8 



cu. ft. The energy is 925 0.091 X 2.5 X 225.8 - 873.6 B.t.u. 



Example 4. With the ilxample 3, find the work done by I pound of 



steam in expanding. 



When steam expands adiabatically tlu- work done is equal to the decrease of 

 energy. MI - 1 138.5 (Ex. i) and M - 873.6 B.t.u.; hence the work is 



H'n - 1 138.5 873.6 - 264.9 B.t.u. - 206,000 ft. Ib. 



Example 5. Steam having an initial pressure of 180 Ib. per sq. in. and a 

 tenijH -rature of 550 F. is assumed to pass through an ideal Ranking cycle. 

 Kind the heat .hanged into work (a) when the steam is exhausted at a pressure 

 of 16 Ib. ; (6) when it i> exhausted at a pressure of 3 in. of Hg. 



In tlu- Rankine cycle the heat changed into work is given by the decrease of 

 the heat content during adiabatic expansion. From the diagram. i s - 12974 

 B.t.u. Following the line of constant entropy to p 16 Ib.. h is found to be 

 1094 B.t.u.. and continuing to p - 3 in. of Hg. h - 950 B.t.u. Hence the heat 

 turned int<> \\.. r k i- !'. >r the first case 12974 1094 - 2034 B.t.u., and for the 

 second case 12974 950 - 3474 B.t.u. 



Example 6. Steam at a pressure of 200 Ib. per *q. in. and quality 0.97 is 

 throttled in passing through a reducing valve. At what pressure will the steam 

 be dry and saturated after passing through the va 



In a throttling process tlu ntent i remains constant. Hence a line 



i const, through tlu- initial \*>\i\i intersects the saturation curve in a point 

 that \\ e*. the ret j u i red final state. The pressure is found to be 44 Ib. per sq. in. 



Example 7. In a throttling calorimeter the observed pressure is 17 Ib. and 

 the temperature 255 F. If the initial pressure of the steam was 160 Ib. f what 



Was the initial tjiial: 



A line of constant i through the point p - 17 Ib., / - 255 cuts the line 

 P 160 11>. in a jn.iiit at which the <|ualit> i> o.> 



Example 8. Steam at a pressure of 200 Ib. per sq. in. and a temperature of 

 450 F. expands in a nozzle to a pressure of 60 Ib. per sq. in. Find the velocity 

 ud l>> the jet (a) when the flow is assumed to be friction leas; (ft) when, 

 due -n. there is a loss of 12 per cent in the energy of the 



If the expansion in a nozzle is adiabatic and frict ionics* the fundamental 



equation of flow is - - - J (i'i - H), or IP - 223.7 ^i - H- The effect of fric- 

 tion is to decrea.^ energy, and if this decrease is y per cent of the friction- 

 less jet energy, the velocity in this case is given by w * \ (i it) (i y). 

 From the diagram tlu initial heat content is 1240, and the final beat content 



