Number of extra papers used if any

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1 Last Nae: First Nae: Thero no. ME 00 Therodynaics 1 Fall 018 Exa Circle your structor s last nae Diision 1 (7:0): Naik Diision (1:0): Wassgren Diision 6 (11:0): Sojka Diision (9:0): Choi Diision 4 (8:0): Holloway Diision 7 (:0): Vuppuluri Nuber of extra papers used if any Diision 8 (1:0): Buckius INSTRUCTIONS Do not reoe staples fro any page. If you use extra paper, attach it at the end of the exa with a paper clip and dicate aboe how any extra sheets were attached. Do not write on the back of any page because it will not be scanned so will not be graded. This is a closed book and closed notes exa. Equation sheets and all needed tables are proided. Significant credit for each proble is gien if you identify your syste and its boundary, draw the releant energy flows on a diagra, i.e., Energy Flow Diagra (EFD), start your analysis with the basic equations, list all releant assuptions, and hae appropriate units and use three significant figures. There is no need to re-write the gien and fd. Do not hesitate to ask if you do not coprehend a proble stateent. For your own benefit, please write clearly and legibly. You ust show your work to receie credit for your answers. IMPORTANT NOTE The use of PDAs, Blackberry-type deices, cell phones, laptop coputers, sart watches or any other sources of counication (wireless or otherwise) is strictly prohibited durg exaations. Dog so is cheatg. If you brg a sart watch, cell phone, or other counication deice to the exaation, it ust be turned off prior to the start of the exa, placed your backpack, and the backpack ust be stored below your seat. It shall be reactiated only after you leae the exaation roo for the fal tie. Otherwise it is a for of cheatg and will be treated as such. SECOND IMPORTANT NOTE The only calculators allowed for use on this exa are those of the TI-0X series. No others. 1

2 Last Nae: First Nae: Thero no. 1. [0 pots] Circle the correct answer(s) (no partial credit) for (a) through (d). (a) [ pots] A constant ass syste hag energy teractions with its surroundgs always operates at steady state. (True or False) (b) [ pots] A flow syste with one let and one exit hag energy teractions with its surroundgs always operates at steady state. (True or False) (c) [ pots] The net work done by a power cycle is always positie. (True or False) (d) [ pots] Which of the followg deice(s) result a pressure drop fro let to exit? (Nozzle, Diffuser, Turbe, Throttlg Vale) (e) [6 pots] Air at 450 K (h 1 = 45.0 /, u 1 =.6 /) enters a horizontal, adiabatic nozzle operatg at steady state with a elocity of 5 /s. At the exit, the air teperature is 00 K (h = 00.1 /, u = 14.1 /). Calculate the elocity (/s) of air at the nozzle exit. Show supportg calculations. de syste Q W h ke pe h ke pe V V1 1 J h h ; 1 1 s s Velocity of air at the nozzle exit: V 551 s (f) [6 pots] Air, considered as an ideal gas, enters an adiabatic, no work throttlg ale at 450 K and flows with negligible changes KE and PE. What is the teperature (K) of air at the exit of the throttlg ale? Show supportg calculations. de Q W h ke pe h ke pe syste h h 1 h f Tonly for an ideal gas T1 T Teperature of air at the exit of the throttlg ale: T 450 K

3 Last Nae: First Nae: Thero no.. [40 pots] A closed, piston-cylder deice contas air at an absolute teperature of T 1 = 00 K and specific olue of 1 = / (State 1). The air undergoes a power cycle coposed of the followg four processes. Data at each state is cluded the table below. Process 1-: Isotheral copression fro 1 = / to = 0. / Process -: Heat transfer at constant olue until T = 1500 K Process -4: Isotheral expansion until 4 = / Process 4-1: Heat transfer at constant olue back to State 1 Molecular weight of air: 8.97 /kol State T, K, / u, / h, / (a) Show the cycle on a P- diagra. Label the axes and four states, show the les of constant teperature, and dicate the process directions with arrows. (b) Calculate the specific work and specific heat transfer for each of the four processes the cycle. Report your answers /. (c) Detere theral efficiency of the cycle. Report your answer %. Identify the syste, show ass/energy teractions (EFD), list any assuptions and basic equations, and proide your solution. There is no need to re-write the gien and fd. Syste/EFD

4 Last Nae: First Nae: Thero no. Extra Space for Proble Assuptions Quasi-equilibriu Ignore KE change Ignore PE change Air behaes as an ideal gas Neglect friction No other work except boundary work Closed = constant Basic Equations Wboundary de syste PdV Integratg: QW U KE PE Q W h ke pe h ke pe P R T air R air R MW air Solution (a) P- diagra 4

5 Last Nae: First Nae: Thero no. Extra Space for Proble (b) Mog boundary work durg copression of the gas fro 1 to : RairT w kol-k 1 Pd d Rair T1 T ln 00 K ln kol w1 198 w < 0 work done on the syste Considerg energy balance for the gas fro 1 to : q1 w1 u u1 q1 w1 q1 198 q < 0 heat transfer of the syste Mog boundary work durg copression of the gas fro to w Pd : w 0 Considerg energy balance for the gas fro to : q w u u u q u q 991 q > 0 heat transfer to the syste Mog boundary work durg expansion of the gas fro to 4: RairT 4 w kol-k 4 Pd d Rair T T4 ln 1500 K ln kol w4 991 w > 0 work done by the syste Considerg energy balance for the gas fro to 4: q4 w4 u4 u q4 w4 q4 991 q > 0 heat transfer to the syste 1 Mog boundary work durg expansion of the gas fro 4 to w41 Pd 1: w Considerg energy balance for the gas fro 4 to 1: q41 w41 u1 u4 q41 u1 u4 q q < 0 heat transfer of the syste 5

6 Last Nae: First Nae: Thero no. Extra Space for Proble (c) Theral efficiency of the cycle: theral w q q H net, For the gien cycle: wnet, w4 w1 79 and q q q theral 0.4 theral 40%

7 Last Nae: First Nae: Thero no.. [40 pots] Refrigerant 14a is contaed a rigid tank of total olue 1 at a teperature of 0C and quality of 10% (State 1). A leak deelops at the top such that saturated apor slowly escapes fro the top of the tank. The leak is stopped when all the liquid side the tank has eaporated and only saturated apor reas the tank (State ). Heat transfer occurs such that teperature reas constant durg the process. (a) Calculate the ass of the refrigerant escapg fro the tank. Report your answer. (b) Fd the heat transfer durg the process. Report your answer. (c) Detere whether heat transfer is to the syste or of the syste. Identify the syste on the sketch proided, show ass/energy teractions (EFD), list any assuptions and basic equations, and proide your solution. There is no need to re-write the gien and fd. Assuptions Ignore KE and PE effects Rigid tank: W 0 One-diensional, unifor flow at the exit Basic Equations d de syste syste Q W h ke pe h ke pe 7

8 Last Nae: First Nae: Thero no. Extra Space for Proble Solution (a) Integratg ass balance: syste 1 1 State 1: f 0 C and g 0 C x 1 g 1x1f V1 1 Initial ass of R-14a the tank: State : g 0 C Fal ass of R-14a the tank: V Mass of R-14a escapg fro the tank through the leak: 1 0 (b) Integratg energy balance: U u u 1 1 Q h Q u u 1 1 h State 1: u f 0 C and ug 0 C 41.0 State : Q 7,800 (c) Q > 0 heat transfer to the syste syste u1 xu 1 g 1x1uf u u g 0 C41.0 Exit State: h hg 0 C61.6 Qu u 1 1h

9 Last Nae: First Nae: Thero no. Extra Space for Proble 9

Number of extra papers used if any

Number of extra papers used if any Last Nae: First Nae: Thero no. ME 00 Therodynaics 1 Fall 018 Exa 1 Circle your instructor s last nae Division 1 (7:0): Naik Division (1:0): Wassgren Division 6 (11:0): Sojka Division (9:0): Choi Division