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ChBE 2110 Final Exam Solution Fall 2007

ChBE 2110 Final Exam Solution Fall 2007 - NAME...

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Unformatted text preview: NAME ‘4‘”‘0 a; 27" 0 N ChBE 2110 Professor Gallivan, Fall 2007 Final Exam ..mw«~wmmmmmwm.——_mm (l) (25 pts) A process has been proposed whereby 1.5 kmol of an ideal gas (Cp = 30 kJ/kmol—K) is taken from P =10 bar and T = 300 Kto P = 1 bar and T = 500 K in a closed system. During the process the system does work, and receives 50,000 k] of heat reversibly from the surroimdings at 300 K. a. How much work would need to be done by the system on the surroundings? b. Is this process possible? ' 0. Would it be possible for the gas to undergo the same change in state adiabatically? Explain. d. Would it be possible for the gas to return to its original state adiabatically? Explain. ‘ t1 .3 T9 [/9243 x1073 wdk (imam WWW ‘ “BX/0733 A S S ~Nle N'PlRQi-ﬂ ald‘] a T. 3-?de p? 79 ﬂ (EM: 1500 m! (30 In f—% 43314 in E _, «r J E s » “SW73 .1 A- ﬁW " “I 11/05 ﬂ _ S Imfbﬁlﬂé ‘ Ang 3 Ag” 45”} *USx/O <O a" ‘ 6- Ass-so :2 Asmajmsyﬁamtg pOSS’EZf gf at. A5»...;v: «6.3/0ng fmﬂaiﬁﬁﬁéj 1 L g \ €551.31 am- (2) (25 pts) Consider entropy as a function of temperature and pressure, S(T,P). a. Derive an expression for the change of entropy in terms of measurable variables. b. Evaluate the expression from part a. for a Censtant temperature process, using the ' virial equation of state Z21+£ RT .. ~ PW? gimﬁit {Vii/{61 :7 7119 are: ens/£17 9x ‘1 D ‘ fwi 4’ i v as -_; 3V 1 09 W t air (at); (El 6 E3 CMSMM‘ It. ML 6130313): %) at p - s La- Nua’ ﬂu"; {m £03 2: i + B? m 75 . 0 U" ﬁiS‘Srma 5J3 Maﬁa/1% [ME/tit] + B ‘ ENE/i 140- fgﬂWir-VZMVVKLJ r WW0? I"; 1. K . 37‘ r3 . P 013:- algae? a P d (' S‘s-A31“ liﬁh‘ot DBL“ (3) (25 pts) Calculate the enthalpy departure function for the equation of state P2 P(V—B)=RT+a—E~ Use whichever version of the departure formulas is most cenvenient: R V ,0 _ P H—= TEE] —P dV+Z~1=I—T[a—Z] f393-4»z—1=—J"r[a—Z] if: RT” 61",, 0 anp 0 (3pr Hardfa €oh"? 6‘" V V‘Bn‘g-Iai 7 p T : pV_ P U a J ﬂ ’02- 5‘23(B+"F”T “ MM‘L‘X"? PT {- P m“ run/Q 92 ,BP‘ ~7- H: _ 10*“ ~89 15001 p ' 4- 0J0; '3 1U" '£!(Q?—"ﬁ1% ENQT - *’ B 2%) +9 . . «f “9+,” 6113 J a RT 1 Wm ' max-1. __ ._ . . (4) (25 pts) A vapor compression refrigeration process using ammonia as the Working ﬂuid is to operate between cold and hot reservoirs at 20 and 80 C. Determine the coefﬁcient of performance for (a) reversible operation (except for the isenthalpic throttle valve); and for (b) irreversible operation. In the irreversible operation, entropy is generated because the working ﬂuid is 10 degrees lower for evaporation and 10 degrees ‘ higher for the condenser, i.e. the irreversible cycle working ﬂuid operates between 10 and 90 C. Assume for the irreversible operation that the compressor is only 75% efﬁcient. Compare your COP’s from (a) and (b). How signiﬁcant is the irreversible expansion in ' the throttle valve? Should one consider an isentropic valve, which is more expensive? 85’s. fQ 3 .. .. .. ._ .. . . mmxmvaur‘. -_ COP: GQS—g‘tO 33g ' 770-928 ‘ H5 “@163 ........ ,IQQ_.M__MEL Wig? + I 9 0 5'0 52 7 0 O. St}! _ ,. I W 3,. 750 35,0 770 {.14 3 7S0 I 820 M ﬂu. W»— ; CW rt’SSWI I _ ‘ 0 79, cos AH; H3 441 770 4220 H3 = 8 1.1,, a J K 3 “ﬂ " 3 I g m I (/05 “3"”; 2/05" COP: H;— H. c 20'170 1m) us 250 5-3-15? MN {1% {SEW’C WM/ 820 -920 A (210 {ISO .. Cop- a /.8 mm— .. . .W, ., m ‘mmm .w EEEE .ﬂﬁ ~‘Ihinha. §§ ‘ . . A65 .mcom am. 3:3 52. mo "35\$:an 5:5 .mma £2“? .ﬂ tum .mmﬁuﬁi 2.82% 33530 Sammy“ .< .m E; £833 .2 .M .auwaom .<. .0 58nd .3558“ BM SENS“. Robsoéguﬁomﬁoh mé manna V ...m:£:3m. .m .‘ .3 ma .3 m6 . #6 ad \ I’d r“z P“;' 08 n a ....>4?ﬁmwﬂm :, . . 7 @ﬂwﬂoﬁnv 4.1. . an. 7 .yliusal. _ \1 .1. «ﬁg», a“. F £5.21?» n r. (man .2335 ﬂ n . .Euﬂmﬁﬂﬂuaw IIIIIIIIIIIIIIII. "l-llll \$rllﬂﬂl‘lllli'.llll.‘ ﬂaw"?Iﬂumﬂﬂmuhummﬂﬂﬁmmmmaw .w huh JAWS»... 9., . ,, ﬂ ._ ﬂﬂmqmmrﬂﬂwﬁwﬂﬂﬂmmmmﬂ. Amwgy Iii ‘iﬂaﬁﬁkmﬁﬂﬂﬂﬁﬂﬁﬁq ﬂﬂuuwyﬁ 2., W mﬂwMM ,2? MMWMﬂmmmnuy m}... .. '1 AN «wu~df“‘l.“lrll§Elli—II.Ilsa. g I_ w. ...
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ChBE 2110 Final Exam Solution Fall 2007 - NAME...

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