Quiz 2 Solutions

Quiz 2 Solutions - WTGERS MAE 14:6502474 Alternative Energy...

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Unformatted text preview: WTGERS. MAE 14:6502474 Alternative Energy Systems School of Engmeenn Quiz 2 (please print) Total Score: Page 2 of 1D ' Mtlltiplo' Choice (4 points each) Figure 1 dopiots on om-oyole ooear. fl'tormal enorgy oomorsion (DIED) system. Use Figure l 1):: answer questions 1—4. VfiWUi‘fi Pumn LOW-PIGSSUT'E 5163M - Gonoramr 3 Direobco ntatt condo war 4 Dissoiuod Gases Warm-51.1 rfaoe Water “tam—Water Discharge Cold-watar Bald BEEF Disch argo "ul'tr‘ator Emmi 1. An open-owl: CITEC system oporatos with warm surfaoo wator at 2TB. an evaporator saturation temporamro of 24‘0, a turbine exit tomporomro of 14°C and cold “oi-or equal to 3°C. The idool (isunlropio) woo: from file turbine is ' K3 ~ _ KT) . a, a. 53.94 kJflcg “7%? ZE‘HSA hag SEA. <85qaq lad K :fbifloaoa mg ) Tczqvc "Tcuwc 1:. 1135.25 kag \(‘3‘ 53'%0* [O-G‘W‘V 996133 = aqugm UJg‘a‘ng-Lt-QWQZBH‘F (33.05K31m d. Noon oft-ho above. 523 : 35:8.5735H= 0-90fiq+$L%v‘50”3"0'30‘tq); X =Q,0\Il$i§ 2. A11 o put-cyclo GTEC systom opomtcfi with warm surfs-co orator at 2?”C, on ovapomtor ooiomtion tempmlurf: ofld'fl, a turbine exit Damp-cram of 14°C and cold wotor at 8°C. If tho actual work domed from tho Lm-hioo is 66.? kakg, tho tmbino ofi‘toionoy is 1:. om: : . vs. a] w - 0.305 4:. £1.95 €3.03‘45ha3. Page 3 of 1D :1. {LEE 3. An openueyele DTEC system operates oath mm smfeee water at E'FC. an evaporator saturation temperature offlnC, a turbine exit temperature of 14°C and cold water at 3°C. The actual work derived from the turbine is 66.? kakg. Determine the mass flow rate required to extreet lflfl kW from the airline. s. seeker do = 129.93. 3 \DOW : Mm 1Ctit/5 I. 3.5m... 03w: unsettle e. 2.351tgfs @te of the age) 4. A11 open-cycle DTEC system operates with warm surface water at ETC. an evaporator saturation temperature of 24°C, a turbine exit temperature of 14°C and cold water at 3°C. The eetnal work derived front the turbine is 66.? kJJ'kg. The enthalpyr of the fluid exiting the turbine is e. 25W.3 kJr’l-tg b. 2645.8 ktkg ha: “33‘ mm «’— 26 L‘iB.‘-‘mi!% e W ,7} 65%“- ZH’W 3%? 24%?ka ,. m”'""""'"* It.‘ ......u.r-'I I .1. 2735.5 1(1ka 5. A 3 meter ocean wave has a period of 5 seconds. The wavelength is s. 45 m l:-. 26m E 39? 7x: \Bflo "CZ :- LLSGXSQIQz seem :1. None of the above 45. A 3 meter ocean wave has a period of 5 seconds. The wave speed is b. 3.5 ma's e. 5.5 mfe Page 4 of ’10 d. 4.5 mite 'f. A 2 meter eeeen wmre has eperied of 5 eecenrie. The density of water is 1025 1:3me and gravity equal te 9.30? men. The tete] energ}.r densityr is 21. 1006.5 I’m" 1:. 5015an Tg=\ 0% :L Suzie) \“V‘ “W 1% <3) 2mm; l 3mm 5) ________ “M 5 5.0Qbe3’ Sim?— 3. A fuel eell has an email reectien: H; + if}; -r ”gem, endideel werk equelte 19303 Jarmfl'l. Avegedre‘e number, hi], - 6.02e23 eteinefniei, electreneharge = q= 1.602e-19 Ceuleinhe. 1heinternel eell reltnge fer this fuel eeli is a LESV I: met: Vlhfifm laigjlmol 400'“ ”MM ....... MR1 ? A W ”9‘0 L2) (\eoae'mllto c2985 c 2.351.: 9. Fer the idle-wing reeetien:L'H+ 4 U: -> CD + H; + 5'3ng the enthalpy,»r ef femletien {if the reaetim, dhflmet stenderd temperature and pressure {STP}ie i - F m a. 38:.65kifmel “Monet?" $3533 I‘m‘ firmed) W050 3:. eeseeknmol hm reorgsmlmd lh%1‘%.®‘c3lmo\ e. -3i}5.55 Mfmel NR Fer-#W' ‘-'— — _. (3| id, _ oi : (”f a. $1.561:er {m {“033 $6335) “ LRWDBW) N... Meme” 2 eggx,3o\<:’>lm\ it]. The current efiieiene}r efe fuel eell is [135, 1when the eetuel current is 6 me and. 2 electrene are transferred ever met efreaetent. Aregadre‘s number, bl, = 6.132623 nemsrnml, electron ehmge - q — 1.6fl2e-l 9 Ceulemhe. The rate at which the preduet is generated is “Ham“..."h FM?” "H“ := \ ,, e. 3.6fie—li mans (‘1 W, L- . - LEW-3’ “M new , h. Ines-e melts , ' m :LO.D(loP‘1’_,__’__.__ .: 3‘ fake—3% (oesilau .eozanXemcfiS 3 FagsSpfw c. 8.53:6 mall's d. Nuns pftim shave 11. Extra Credit If: paints} An ocesnthsrmsl energy mnvsrsipn {UTE-C} system is ssssmially shat snaps, wimp the Camp‘t sfliciency represents an upper bound on the thermal efficiency. For an open- L'ycle OTEC systsm Tlmt ppmtes with warm sat-fans waits: at 2?"C, an evaporator sstmalion tampsrahsrc pf24°C, Lmbim: exit tsmpmiurs of 149123 and salt! Wm at 3°C, rim (1th pflicipnpy ofthp 51:15:11 is a. spas in (1:125 57 11- Q Q U c 2.78.! + - s33 +8 W P: W k? 0.34:3} 1mm: “— 2336*?“ ri. nuns pfths shove Problem 1 (8 points) a) Calculate 1h: svailablp (mp-1'33»r from a tide with a. 12 meter range and surfapc arcs. equal to 1:6 .112. Th: density pfwaxsr is 1025 kgr'm and gravity equal In 9. 8|]? mfs. Use Frames] 1 {Scensrlu 1}. III. '5: I. Qfiagli f 10; fiat—fit fl ri'h' 1! {rs 1: {LE (- J‘Ji w {EL} E x. u 3. 1h“) “.3: 3m“: i: T» r: Jill iffy-Z} 2-2.?- gig-#311 '3‘“ .f' Eli-E." :3 C ”7:“ ['(HOMWM 3 :3 a c5 “‘4‘“ in) CaicuIsts fllfl available energy-1590111 a 11:53 with [[2 master range, surfapas ales pqual to lsfi m’, and a = 0.13625 11'1 when the energy is harvestsd helm ll=1 11an- snd t1 = 4 hour. Um Prat-Jpn] 2 {Scenario 2] Page 6 01°10 Problem 2 (24 points) A close—cycle Ocean Thermal Energy Conversion system is depicted in Figure 2. Ammonia is used as the working fluid. The warm water surface water enters and leaves the evaporator at 28°C and 25°C respectively. The ammonia exits the turbine at 12°C. The cold water enters and ieaves the evaporator (condenser) at 5°C and 8°C respectively. The overall heat transfer coefficient for both the evaporator and condenser is 1400 W/mz. The quality of the ammonia at the turbine exit is 0.988. Vapor me- Turbine Generator Heat Exchanger (Boiier) Cool Water Intake Warm Surface Surface Water Cool Water Water Discharge Discharge Figure 2 a) What is the temperature at the turbine entrance? (3 points) s/3;W\X UK: Page 7 of 10 e) The actual work from the turbine is 12.31 kJ/kg. Determine the efficiency of the turbine. (3 points) (“yr _ iwiwfflkfivk: a, K}\~-}(1€§;Efxr.)a& “MW ..._._....,_._M.,. iii d) The mass flow rate of the ammonia is 10,000 kg/s. Determine the power extracted from the turbine in units of kW. (3 points) (vi = we «r i\ 00 ‘“‘“ 5 3a.. M OW “WW rattan . 6) Determine the evaporator (boiler) surface area. (10 points) Page 8 of 10 f) Extra credit: Determine the warm—water mass flow rate. (4 points) (i Q r w " /' fl, . V \ Meme “1"“ (Dr: ‘33 {£3 {1111935}? "W mm Mm w w MAmWMMMW ” M 51": V3 {23:33 h (“333- ~ 9 :. . r’ f“ r: , I‘m {mi/{fl a; 6t; % UT V5266»? Huge-53:: . e ‘ Jr?» U393} 0/ w ”WW. .WWHJJW Problem 3 (26 pomts) ‘ .3 vw-‘u‘kq A fuel cell uses methane for its operation, where the overall reaction: CH4 + 02 —> C0 + H2 + Hzoaiq). Avogadro’s number, N0 = 6.02e23 atoms/mol = 6.02e26 atoms/limo], electron charge = q = 1.602e—19 Coulombs. a) Write an expression for the change in Gibbs free energy for the reaction at a temperature, T. (10 points) m3; 3; :2: . 3x; fl ,3 WW WW , mg {33 333;; 3; h N. “WW k b) W111 {he réactlon Bé favorabie When TM Page 10 of 10 e) The actual current and voltage are equal to 1.5 amps and 0.6 V, and the thermal efficiency is equal to 0.85. Determine the fuel cell efficiency. (4 points) ...
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