Summer 10 Exam 2 Key

Summer 10 Exam 2 Key - MEEN 315—Summer 2010 Exam 2 Name K...

Info icon This preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: MEEN 315—Summer 2010, Exam 2 Name K E 2 Section Number 1. Please put your name on e_ve_ry page. 2. RELAX, this is only an exam. Read over the whole exam, then decide which problems to work first. 3. The exam is closed book and notes. Tables are provided. No collaboration with others! 4. Include a sketch, and clearly state assumptions and equations used on problems requiring detailed analysis. 5. If you get stuck on a problem, go to the next one. 6. Problems must be worked in the unit system in which they are specified. Failure to do so will result in a lower score. 7. Assure that you have 12 different pages, including the formula sheet as the last page. AN AGGIE DOES NOT LIE, CHEAT, OR STEAL OR TOLERATE THOSE WHO DO --- _-- --- _-- _-- —-- -- MEEN 315—Summer 2010, Exam 2 Name Section Number Multiple choice problems worth 2 pts each. Circle the answer that is the most appropriate or closest (numerically) to your answer. 1. An oven preheating is an example of what type of process? a. Steady State, Steady Flow b: Isochoric “TevaiCpemture iS chm/19mg Transient l (J, «,6 ® Throttling LU h 2. To increase the COP of a Carnot refrigerator operating between the temperature range TH and TL you can: ‘ / W 7 P .. TL 7 H. {z TL I‘ b. Increase Wln C 0 f . - - a ‘ T” I TL <- 3. For steady state, steady flow process: dEcv/dtzo, dmcv/dt:0 b, dEcv/dtCV750, dmcv/dtséO c. dECV/dt=dw/dt, dmcv/dt=0 d. dECV/dt=0, dmcv/dt=d\y/dt 4. The enthalpy of a substance undergoing a throttling process: a. Decreases b. Increases Q Does not change (1. Increases by a factor proportional to the kinetic energy gained 5. The following is one of the Carnot principles: a. The efficiency of an irreversible heat engine is always more than the efficiency of a reversible one operating between any two reservoirs. b. The efficiency of an irreversible heat engine is always more than the efficiency of a reversible one operating between the same two reservoirs. ® The efficiency of an irreversible heat engine is always less than the efficiency of a H reversible one operating between the same two reservoirs. d. The efficiency of an irreversible heat engine is always less than the efficiency of a reversible one operating between any two reservoirs. 6. A (a) is a device that increases the velocity of a fluid at the expense of pressure. A (b) is a device that increases the pressure of a fluid by slowing it down. What words belong in the blanks? . (a) Compressor (b) Diffuser {$1 (a) Nozzle (b) Diffuser (a) Turbine (b) Compressor d. (a) Nozzle (b) Compressor MEEN 315—Summer 2010, Exam 2 Name Section Number 7. The entropy of steam will (a) as it flows through an actual adiabatic turbine, and the entropy of the working fluid of the ideal Carnot cycle (b) during the isothermal heat addition process. What words belong in the blanks? .T. a g Q (a) Increase (b) Increases 6‘ T b. (a) Decrease (b) Remains the same c. (a) Remain the same (b) Decreases d. (a) Increase (b) Decreases {If m s a») 5 8. An ideal gas is contained in a rigid container. The gas undergoes an isothermal process. What is the entropy change (kJ/K) of the process? 6%? AU’;O 47:0 #9 A510 c. 1.40 d.oo 9. The polytropic constant of an air experiencing an isentropic process is: a. 0 $140 Pu’K: Constant“ d. 00 - K: 1.11 10. A heat pump absorbs heat from the cold outdoors at 3°C and supplies heat to a house at 20°C at a rate of 4 kW. If the power consumed by the heat pump is 3kW, the COP of the heat pump IS: a. 0.33 \ @133 L q KM/ 97‘ MEEN 315—Summer 2010, Exam 2 Name Section Number 1. R-134a expands in a reversible adiabatic turbine from 200 psi and 200 °F to 10 psia at a rate of 12 lbm/s. Determine: a. The power output (hp) of the turbine (6 pts). b. The exit temperature (°F) of the R-134a (6 pts). c. The entropy change (Btu/R) of the process (4 pts) d. Draw the process on a T-s diagram. Include the numbers found in (b) and (c) (4 pts). \ . I I ' . ‘ I . Corn rnp:Me=Mw CoEaMfi-M(hriw) Enifo Pt}- Balantel Sf: 56 §{a{‘(’ 5L " _ b . \ P:_)ooP m " ’11:: 19:9200 P914 376‘ ° '_ - O T: 100°}: 0 W 7" 2‘ 00 F 8f“ = I 3 8 ‘74 ——,6 m , ') — A ‘ Mom 3’ 01%35 ,% \Vzm (him he) K B‘I‘H «1&6 I AP ( 2 “$83? Isak :( Mg; (139 (W 108 mfgfl um; owes W: 5.22 K75 hp MEEN 315—Summer 2010, Exam 2 Name Section Number 2. Air at a pressure of 1.4 MPa, 300 0C is flowing in a pipe. The pipe is connected to a rigid evacuated tank by a threaded globe valve. The valve is opened and the tank fills with air until the pressure in the tank reaches a final pressure. Assuming the process takes place adiabatically, kinetic and potential energies are negligible, and specific heats are constant, determine: a. The appropriate simplification of conservation of mass (7 pts). b. The appropriate simplification of conservation of energy (7 pts). c. The final temperature (K) of the air in the tank (6 pts). aim; hi 2 ’47th mi i’li :n’lzdL ”7;: W); b; r Li). LPL": J; 71: KT: =(/.4)(573)/< MEEN 315—Summer 2010, Exam 2 Name Section Number 1 3. An uninsulated mixing chamber has two streams of water entering. Steam ¢MPa, 500 °C) enters at inlet lwith a mass flow rate of 2.0 kg/s. 0.5 kg/s of water (2 MPa, 30 °C) enters at inlet 2. A single flow exits at point 3. The mixing chamber has a heat loss of300 kW. Determine: a. A sketch of the system described. Include given information (5 pts). b. The mass flow rate (kg/s) of the exiting stream (5 pts). c. The state of the exiting stream. [If the stream exits as a super heated vapor, use temperature (°C) and pressure (MPa) to describe the state. If the stream exits as a 2- M 2 2 B phase mixture, use temperature (°C) and quality (%) to describe the state. If the stream ' exits as a subcooled liquid, use temperature (°C) to describe the state.] (10 pts). _ 4:» [email protected]:300Kw COM: ml+iiflLefiq320 930°C . . State! $156.: Pg; rm PS; MEG . :§00°C 7—2300 , KT . J’ .v : ,. h=39é83 52; h—Iv—vél‘r W77" r9 MEEN BIS—Summer 2010, Exam 2 Name Section Number 4. A power cycle receives 1000 kl of energy by heat transfer from a reservoir at 1200 0C and discharges energy by heat transfer to a reservoir at 30 0C. Determine: a. The minimum amount of heat transfer (kJ) to the cold reservoir. (5 pts). b. The maximum amount of work (kJ) that can be produced by the cycle. (5 pts). 0. The maximum efficiency (%) of the cycle (5 pts). d. The entropy change (kJ/K) of the cold reservoir (5 pts). Q/L _ ’TH ,— [000/57; [#73 K / M/nf-E QC TC QC 3 O 3 F QC: 105,70 kr E) WM: lGOOvQOSJO : 7941,30 KT c) ’7), Wne‘i' V ,_ 7QLI,30 *loo 5 / QM ’ IOOO f4! 10 MEEN 315—Summer 2010, Exam 2 Name Section Number AP=pgh Pv = RT PV = mRT Pv:([email protected] Weed =V-1212R W: [W W=m1Pdv dh=deT 2'71 _ Z ".1” = d121, vx= Vf + x(vg-vf) ux = Uf + x(ug — Uf) hx = hf + x(hg — hf) mic-Ix mule/x W 2 If . d5 F = kx (linearspring) SG=p/pH20 du = cvdT h=u+PV X: mvnpur AKEZ‘l—m(V22—Vlz) APEngZZ—Zl) Inliquirl + mvapar 2 cp =cv +R Q—W+ 282,111,. +V,2/2+gz,) — 27710010 +V02/2+gzo) = dE/dt inlets Guile/s q-WZAU+Ake+Ape Q _ W ___:_t(U + KE + PE) Q'WZAU+ AKE+APE ffig g 0 Clausius Inequality dS : 5Q/T'"> TdS : du + PdV TdS = dh —- VdP T reversible V — V V AS=S§—s§’—I-'\’Inp—2 szufornfl W=p1V1In—2—forn=1 p1 _ ’7 V1 AS=CPln(T2/T.)-Rln(P2/P1)]. P1 _ P11 V1 _ Vrl isentropic, variable ideal gas,constprop ————— ——— . _ AS=CV In(Tz/T1)+Rln(V1/V1) P2 Prz V2 Vrz properties, ideal gas As=Cp1n(T2/T1) incompressible p v k —2 = —1 isentropic, ideal gas p1 V2 W : QH ' QL Q . 1 (k—1)/k k—l AS = — heat reserv01r 12 [P2] [V1] 1. . . — = — = — senlro 1c,1dea] as T T, p1 v2 P g (QH/QL)rev = TH/TL COP = QH/Win (heat Tl = Wnet/QH (heat engine, power COP = QL/Win (refrig. systems) pump) cycle) p V2 -Pz'R+I/22’V2 E =ri1e 6mm“ : — + 7 + g2 - Aemechw p 2 l +g(ZZ ‘Zl mech mech onedimensionalflow :rh = pVA IDEAL GAS CONSTANT: Ru: 0.08314 bar-m3/(kmol-K) Ru= 8.314 kJ/(kmol-K) Ru= 1.986 Btu/(lbmol-°R) Ru: 1545 fi-lbf/(lbmol-°R) 5Q W W (ke) (ke) AS = — + S = S ; = a ; = a ; = ‘ ll T l, “c W1“ w “n (ket “d (ket dSm, Q - . . - dz : Zi— + iggmmsm — Ugly/smmsau, + ng AS = ($va forresewoir 12 ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern