ME302 s06 thermodynamics exam2 part1

ME302 s06 thermodynamics exam2 part1 - Name _ ___~ _ .J___...

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Unformatted text preview: Name _ ___~ _ .J___ ME 302 THERMODYNAMICS Spring 2006 Exam 2, Part 1 Instructions: 1) The exam is worth 100 points, 40 of which are given for this part. 2) Show all your work and clearly mark your final answers. 3) No assumptions or system boundaries must be identified for this part. 1. (4 points each, 40 points total) Answer the following questions briefly: +2.2. 21) Is the refrigeration cycle below reversible, irreversible, or impossible... QC = 1150 kJ, chcle = 230 kJ, and QH =' 2300 kJ. Recall 5 = Qc/(QH — QC). Why? / 3‘ TL.) ( A "\l 3 ’T“ a\1 .' QC YOU C 3 72m: ’_ 33b. USO ‘ W” b) Write a complete statement of the Second Law of Thermodynamics. Not two statements. Not three statements. Please write one and only one complete statement of the Second Law of Thermodynamics. AS43541.“ (car;an DWAA'Q (av-s a crack at f/o'Juuc Wk (Ail-.314 / (9MMMVI;C'\4;A> oflwg) m c) Cycle A and Cycle B are reversible power cycles which operate between the same two thermal reservoirs. Cycle A has air (ideal gas) as the working fluid and consists of two isothermal and two constant volume processes. Cycle B has water as the working fluid and consists of two isothermal and two adiabatic processes. If possible, compare their thermal efficiencies. I EQVVS‘IbLQ VOW (5&(25 Mans Codiiitifir 0/ / bo-l'ifi “Doc/U so 414 engine/rote; ova £041“ Mfiyimmms arm;Z Same. Ada/mu Vzwixvv'f: WM 1“ : "174 A '73; 8 a. u dufik'fip we SM}; d) In the figures below, energy transfers occur in the directions indicated by the arrows. Identify which, if any, of the devices are possible? - may 15 9055;”, Q) Q“ Q) Q“ fl—L w chele w chcle and/ or e) Below is a system producing work while communicating with a single thermal reservoir. Is this possible? Piston State 1 9 Heat input to system producing work -) Piston State 2 v>2$ \ greasy f) Friction from sliding and friction in the flow of fluids are both examples of irreversibilities. Provide two more examples. , ‘ . Chmitak fizaciion (it (OMLMS‘L/IM) (Lv‘M'U‘i M'X'Hj auc+/;cq\ {asl'j-i-anoL Ll airmen/4km A Jrirmza UL «L/UL ‘ZXQO‘HS {om bkflaling g) What assumptions/ statements can you make about a system which is analyzed with the following equation: 2 2 ‘ Wm, =m[hl .1»,2 +_V1__:_V2_] 8? L0 0M \AQi/wi’ui‘ ' 2 \/ : 0 .3 0% SfiS‘lzm 9’“ Eat?!) 5 h) For the system analyzed in the previous part, the following applies. . .state 1': h = 700 kJ/kg and V = 2 m/s, state 2: h = 400 kJ/kg and V = 30 m/s, and the mass flow rate is 1 kg/s. Is KE important here? i) Air contained in a piston-cylinder is compressed adiabatically. Compare the magnitude of work input during the compression for an actual compression versus a reversible compression (fill in the blank). W < | WI?! V actual _a j) In the tank below, graphically represent (i.e., draw) a system of R134a with quality = 0.5. IP—____________________________i Name Mam gVDm ME 302 THERMODYNAMICS ' EXAM 2, Part 2 Instructions: 1 1) The exam is worth 100 points, 60 of which are given for this part. 2) Show all your work and clearly mark your final answers. 3) Be neat. Partial credit can only be earned if I can follow your solution. +35” 2. (60 points total) A vapor power plant that uses water as its working fluid is shown in the following figure. The mass flow rate of water through the pump is 79 kg/s. KB and PE can be neglected, as can all stray heat transfers. Determine the mass flow rate of cooling water through the condenser (20 points) and the overall thermal efficiency of the power plant (40 points). Qin p, = 100 bar bk 1 ’7‘” ’g '1‘.=520°c 3“ 9 ZE=O=PE O30 Cooling FIND: an“ .15 4'0“ water in at 20°C C‘J‘VEA/ @- Condensei’ OW\ My p4=l00bar -*.> +5 slams) Srlnxk 4 T4 = 43°C COOlIng m _‘,.o W b .I water out at 35°C P a“! .2 0 °“’) KE 3 o 2 PE 1:0.08’bar Power 3 gaturated liquid \ m ‘ {MS 092-“ 09/00:; )‘L ‘ Qrmu; 3’“ E o ‘ M75fw We ‘3 22"" W "5&5 M) : nit ("was 1 -2336.6‘;) - - kl . §l°C _ ‘i ’ {m(uw—u3\ 3 “W 4’2 ‘ I or)”: M]! 109?.‘1 *5/15?) k '73 ‘ ‘ L“ J ( 74% (“‘4' ‘87) ‘ to tn 3 2334.69 kE/lrj 63%: o q ’45,“ g ‘ (w OJQIIZ+V;\(J’W\‘LV.) y.,. a n— X a / a 2 51k“ 331513....I56'3') ’- /4 MW : new? 5/13 AM ” Q 0’10 . — ~-._ 552 cl'éw f, (A) / c I a, a “G . / 0))1 1“ z} + W}q* I ...
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ME302 s06 thermodynamics exam2 part1 - Name _ ___~ _ .J___...

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