Exam 1 solutions - 7,61 , ' 1. (£0 Define or describe the...

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Unformatted text preview: 7,61 , ' 1. (£0 Define or describe the following terms with a single phrase or expression. 9 a. adiabatic /V0 heal transier/ Fe mini/l7 I'Vls’M/Qléyc’j ; b. polytropic process flows: fm’ Mil/(A pl/ntmli' c. equilibrium We flermdyfl‘fmw filial? 0‘; WW’k/‘EE [/MI‘C/ [5 Omaha gm? J (1. critical point m 7‘72/0 01! five. MOW/36 ’ J e. intensive property A Prop? [n (9/6,??lf’fJ/tai? J? [474755 3 f. heat We 5P=m1£anecuf 10%.! if {ff/8'7}, Cami” wg/jflm bw4‘n..c/grf Mote a ‘/?m/)€lell4r€ fi/Jéérfnoc 5 g. List three es 0 thermodynamic work. typ g H i I POW film” »/ m/t ,/ (4 pts) h. What is the specific enthalpy of H20 at 150°C and 4 MPa (kJ/kg)? 11,: th- ’UL (10717504) _, 3 652.3? + .08/0fi(4030,_ C Q 3 Q. A; 5/52 (4 pts) i. What is the gauge pressure at t1: bottom of a bucket of water 0.3 m deep (kPa)? Ea 79%(3W) {KR ,= 33?: W ; 2,74 2% M i 4 / £911 A/jL Please! Be neat, write out equations before inserting numbers, and circle your answers. If you cannot figure out one part, assume an answer and carry it through the other parts. 47 2. (46%) An inverted piston-cylinder device contains 4 kg of water initially at a pressure of 1500 kPa and temperature of 250°C (State 1). At this state the frictionless piston is pushed down against a set of stops as illustrated below. Another set of stops is located toward the top of the cylinder. The ambient pressure and temperature is 101 kPa, 25°C. The cylinder has mass of 180 kg and a pressure of 1000 kPa is required to support the weight of the cylinder if it is unconstrained. Cool air is blown over the outside of the un-insulated cylinder causing the water inside to cool until the temperature of the water is 25°C (State 2). If the cylinder comes to rest on the upper stops stops, the volume is 0.2 m3. a) Does the cylinder come to rest on the upper stops _at its final state (State 2)? Show how you know whether it does or not. 4" X 9 ’V" (14 /m 2/ PM} .I r b) What is the pressure of the water at its final state? 7 A Q What is the‘phase region for the water at State 1, and if it is saturated what is the quality? C a) What is the phase region for the water at State 2. and if it is saturated what is the quality? J Q What is the phase region of the water at the point where the piston just leaves the lower stops? < 9) What is the work for the process (kJ)? { 3) What was the change in potential energy of the cylinder per m of downward movement? ) h) Qualitativer (no numbers) sketch the process on a P-V diagram and label end points. hm) unit) ‘« M'W ‘1 43) Qualitativer (no numbers) sketch the process on a T-V diagram and label end pomts. 9 M .1 m3 -,’q:fiT’$T ' 8 T:(§% 1 \l 0 U1 \ 5m$ Lbju <14 -, . . ml / 55kt L />’ >4 v’l‘7’pi 5‘ .\\\\\\\\\\\\\\\\\\\\\\‘ f) : , : i3,/é4 < /000 M: I? /¥w‘-// “5% Z )4? /l ‘ / Since {PL Vo/amz Lum'fi" ) ' ‘ l L“! ’M‘H'l’r", .. ' ljiw r/L' , , _ .Ll: 0 awn/.44 g T« l p T- " 5 K ) DIV 4 L 4 /( r; -- - 7 + .3. 74/7 W1 — z/L‘l' ~ )5" I zxa Problem 2 continued V") L w High , Sail 3. (30%) Exxon has found a high temperature/pressure under round reservoir of methane (CH4). Consider an underground pocket having a fixed volume 245‘ 3 that contains 40 lbm of CH4. The initial temperature is -40°F (State 1). The pocket is then heated by inserting an electrical resistance heater to a temperature of 75°F (State 2). Y ( Wait/ILA /,l a) If you assumed that the CH4 is an ideal gas at the initial state find the pressure in the pocket aqState IXpsia). b) Is the CH4 an ideal gas in State 2 after the heating? Show your calculations of the compressibility factor. c) What is the pressure at State 2 (psia)? d) For the 40 lbm, find the change in the total enthalpy of the CH4 from States 1-2. Assume Constant specific heat for the CH4, of Cp = 0.53 BTU/lbm°R (Table 3e) and that it behaves as an ideal gas. ‘ I I Wt...umwmywmamnxm—WWWWVWMMW 1. HI i I ____,r r - (‘mnprmsihiiiu factor. X I l'v/Rl‘ I) l,“ 2,0 3.0 Jpn 5n ml .,u Reducer! pressure. PR Problem 3 continued ’0 T 535 .. e 25) 7:: f ' 3'47? /’5 7/]: 3/”: : 40"” f fl /5’45 1% 342. 7 vz /6 [7213“ #7” 25 5 0'] > I 74‘56X4 6,0123% 4/ 7:1/5é +V,'=.036 :7 z: .83 /\/o [70% an lflzfifl/ 7575/ a) ms 0 weawwavwm > S é 51’ or EV’ZmKT‘ 760W5):,?3(-40)l7?3535 C] H 6. 7 2352);)514 ‘ 4) AH= MHz-T.) / i : 40 [gm /. 53 {3% )[75 4-40)] 4. 34; (W ...
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This note was uploaded on 01/27/2012 for the course ME 326 taught by Professor Schmidt during the Fall '07 term at University of Texas at Austin.

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Exam 1 solutions - 7,61 , ' 1. (£0 Define or describe the...

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