Thermodynamics - Final Examination Questions with Solutions | ENSC 2213, Study notes of Thermodynamics

Download Thermodynamics - Final Examination Questions with Solutions | ENSC 2213 and more Study notes Thermodynamics in PDF only on Docsity! ENSC 2213 Thermodynamics PRACTICE FINAL EXAM NAM (15) Problem 1. A rigid container contains 5 kg of a gas (R= 0.4 kJ/kg K). The gas in the container is heated from 25°C to 75°C. The gas can be considered ideal. Calculate the total change in internal energy, in kJ, if the heat capacity is represented by Cv =3.6-0.00IT . R tEl 'i',- Z'li' ,I - iGo •. ~ 1- ?4f1.',. (pf ~lIf)((1.b)-.fXl'T") _ Mi'f _0.0004 1 /. , . ~'f9 ~ I, '1'1 T - ,0002. -r ~ Iz.Q3 _ (J,'1Io(('H'f\' .o~02. ("'12)'1) _ (',<410( (~i'~) - .000"'2. ('Z.Jlf)'l.) ~ J.lH,g, qlLl) ,.......,61..{ ~ 6",5'1 ~ ';, AU=' Lt.>~'P(%)(~~) [A~-;: 7%.", "l kJ 1 Answer: 327.7 kJ NAME ------------ENSC 2213 ThermodynamicsPRACTICE FINAL EXAM Problem 2. Air (assume ideal gas, Z = 1.0) is contained in a piston-cylinder apparatus, as shown below. The cylinder contains "stops" which limit the travel of the piston between the upper and lower volumes of 0.6 and 0.2m J , respectively. The piston may be considered frictionless and "floats" when the pressure is 500 kPa. Initially the piston is pressed up against the top stop. At this condition 3.66 kg of air at a temperature of 400 K and volume of 0.6 m3 is contained in the cylinder. The air is then slowly cooled until the volume drops to 0.3 m3• (For air, use R= 0.287 v kJ/kg K = 0.00287 bar m 3 /kg K, and Cv = 0.72 kJ/kg K) Z ~ 1.0 ':.)1-'ldu.( G,'l-~":t'" a) What is the initial pressure (kPa) of the air? V, b) What is the final pressure (kPa) of the air? ~':. f;,Cb.~)' •• f;oo ;'I"l\] (35) c) What is the final temperature (K) of the air? /. r: I . ," ( .••.•V1.) ::::;~-;0 1", v, x=') d) How much work (kJ) is done by the air during the process? ~J' W~ II ~""cz. c~ '"7 =) fJ; 1 c~f~ ••1- VV " f (v'- -V J )' :: > ~iJO t;;) ( IN '" '-t~o.'ILJ] ) .' e) How much heat (kJ) is transferred to the air during the process? c..v(T~-T,~ \():: w-t- ~ Q =. - / ~o-t t().h fix) (1.&.6~ \( N l.p - .,ooX) (Q ~ - 8'Z-'>,~ ~ JcJ] Answers: (a) 700 kPa, (b) 500 kPa, (c) 143 K, (d) -150 kJ, (e) _ 827.2 kJ I!'I'=======================================- - ENSC 2213 Thermodynamics PRACTICE FINAL EXAM NAME _ (40) Problem 5. Consider a Rankin cycle with water as the working fluid. Superheated vapor enters the turbine at 480°C and 10 MPa and exits at 6 kPa. The turbine has an isentropic efficiency of 80%. Determine for the cycle: "':",~ .•.f=_ Zoo't.~t ~ ... A,. ~ It," )1,( "', -4.s) <~') - - ------- Jo) It .••~_I ? I. S )-A3 ," - , p ~: f"Z. -:',0 ttl , •••.. ?'If '" O. go (a) The actual turbine work (kJ/kg). (b) The actual rate of heat transfer from the working fluid passing through the condenser to the cooling water (kJ/kg). -r (~.r'-"""\'. ,,0.,. '\ k:-;"~U," ~ >.~',~"'h=h~-....J4!cr" /T. -:...,IV '- -""" ----- I J ' p, =!'f: /00 ~.v- A,,- ,,51.P ':; b.floH -.~~I :2 ••o~.~- I St.s.., V. ",..,0'/ - .'i"ll , I ~ ~) ~c~~ '71 (/It."Atl) ~ C! e)(;n/.,:.. z.,o~.H) ~r01~,q ID I \V~--- ~- Answers: (a) 1049.3 k.Jlkg, (b) 2120.6 kJ/I{g ENSC 2213 Thermodynamics PRACTICE FINAL EXAM NAME ----------- (40) Problem 6. An ideal cold air-standard (constant specific heat analysis) Diesel cycle operates under the following conditions: v (: ~ ~ Z. t v't r = Vx; " /1)v.• - h.'" /.'1 f (.3-1 Z ""_1 ~ -:: II) o.~ \ j, '1 ( Z .- / ) / #,. .' ~ V I / V 2 = 17 , V) / V 2 = 2, PI = 95 kPa , T I =_~5 °C , k = 1.4 For this cycle detennine: ~'l 'i!) (a) The thermal efficiency. - -' (b) The temperature (K) and pressure (kPa) of the air at the end of the compression process. (c) The temperature (K) and pressure (kPa) of the air at the end of the heat addition process. (d) The temperature (K) and pressure (kPa) of the air at the end of the expansion process. A,ocL,.~ --, (. a.) .-.-'/' I • \ f7:"' ~ -= ';J~T,::) /} ~ f'"•.•It. -;;."/2 ( q.'l.-r.~ I ~ L-' ~ ~ ==("Pt -;;. So IS .~'fjJJq 1 d)?- ' Pv,rC:\ '"~) -,;,; 7, (ric; (' .) II" (::' \'\ IT" ~rL."K I Answet"s: (a) 62.3%, (b) 925.5 K & 5016 kPa (c) 1851 K & 5016 kPa, (d) 786.4 K & 250.7 kPa