ME 200 Thermodynamics I Spring 2014 Examination 3 Thu 4/10/14 6:30 7:30 PM WTHR 200, CL50 224, PHY 112 LAST NAME FIRST NAME

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1 M 00 hrodynac Sprng 014 xanaton 3 hu 4/10/14 6:30 7:30 PM WHR 00, CL50 4, PHY 11 Crcl your dvon: PHY 11 WHR 00 WHR 00 CL50 4 CL50 4 PHY 11 7:30 Joglkar 9:30 Wagrn 10:30 Gor 1:30 Chn :30 Woodland 4:30 Srcar ntructon: 1) h a clod book/not xa. ) Wrt lgbly 3) You ay u a -30XS calculator. 4) Wrt on only on d of th pag. Work on th back d of th pag wll not b gradd. 5) Falur to how approprat aupton and bac quaton for Probl and 3 wll rult n lo of cr. 6) Provdng a nurcal anwr wthout howng work wll not rcv cr. 7) f you gv ultpl oluton, you wll rcv only a partal cr although on of th oluton ght b corrct. Dlt th oluton() you do not want gradd. 8) Plac anwr n th box provdd n varou part of th quton. 9) Show unt for all nurcal anwr. 10) f you ar caught chatng you wll gt a zro for th xa and your na wll b turnd ovr to th Dan of Studnt. OAL POSSBL SCOR YOUR SCOR Quton 1 Quton Quton 3 OAL 0 Pont 45 Pont 35 Pont 100 Pont ~0~

2 Probl 1 (0 Pont): hr ar two part and tandard oluton forat not rqurd for th probl. (a) (10 Pont): Ar at at and 580 R coprd adabatcally and rvrbly n a tady-flow dvc to a fnal prur of 1 at. What th fnal tpratur f th pcfc hat not contant? U abl A, Ar Stat P, at, o R o Btu/lb- o R ?? / U abl A, Ar = 960 R (b) (10 Pont): On kg coppr ntally at 300 K and 0.5 kg alunu ntally at 500 K ar placd togthr to rach a fnal tpratur of 410 K. Fnd th ntropy chang (kj/k). Cu, 1 kg, Cu1 = 300 K Al, 0.5 kg, Al1 = 500 K Cu = Al = 410 K!" #$ #$ % #$ & #$ & #$!" %!" &!" &!" 1'0.385) '0.903) *+/, ~1~

3 LAS NAM FRS NAM Probl (45 Pont): Gvn: wo lb/ (.0 lb/) of aturatd vapor R134a at 30 lbf/n ntr a copror. h copror dlvr R134a vapor at 10 lbf/n and 10 F to a condnr. h condnr rjct hat to th nvronnt at 70 F and dlvr aturatd R134a lqudd at 10 lbf/n. Fnd: (a) Show th do, labl tat and proc 1- and -3 n th - dagra n th dagra blow; (b) Coplt th tabl on th nxt pag (Do not ntrpolat tabl but u th clot tabl valu); (c) Calculat (c1) th work nput (Btu/) to th adabatc copror and (c) th work nput (Btu/) to an ntropc copror wth th a nlt tat and th a xt prur (tat ); (d) Fnd th ntropy producton rat for th adabatc copror, n Btu/( or). () Fnd th ntropy producton rat for th condnr, n Btu/( or); Aupton: (1) Stady Stat, Stady Flow () Nglct K, P (3) No hat tranfr for th copror (4) No work tranfr for th condnr Bac quaton: d = ɺ ɺ d = ɺ ɺ V Q + ɺ W ( h + + ɺ V gz ) ( h + + gz ) H,L B,S = + ɺ σ + ɺ ɺ Syt ktch: H,L 3 Cond hro Cop 4 vap ~~

4 Soluton: (b) Stat p (lb f /n ) ( o F) h (Btu/lb) (Btu/lb or) (c) d = ɺ ɺ = 0 ɺ = ɺ = lb / 1 d = ɺ ɺ V V Q + ɺ + + ɺ + + = 0 ɺ W ( h gz ) ( h gz ) W C = ( ) = Btu / H,L B,S W ɺ = = 4. 7 Btu / CS ( ) (c1). # = Btu/ (d) Copror: Adabatc, = + ɺ σ + ɺ ɺ H,L o ( ɺ 1 ) = ɺ σ = ( ) = Btu / R (c) 1#. = -4.7 Btu/ o (d) -.#3 = Btu / R () Condnr: - H rduc, rrvrbl H at nvronnt tpratur of 70 o F cau σ ɺ Q = + ɺ σ + ɺ ɺ H,L Q ɺ 161. ( ɺ 3 ) = + ɺ σ = + ɺ (.. ) σ ( ) () -.#/0 = Btu/( or) Q ɺ = ( ) = 161. Btu / ɺ σ 161. o = + ( ) = Btu / R ( ) ~3~

5 Probl 3 (35 Pont): Gvn: A CO tra wth a flow rat of 1.5 kg/ at bar and 700K (tat 1) xd wth anothr CO tra wth a flow rat of 1.5 kg/ at 1.5 bar and 300K (tat ) n a xr. h xtur (3.0 kg/) xt th xr at 500 K and 1 bar (tat 3). h tpratur of th urroundng nvronnt 300 K. h pcfc hat of CO (c p =1.014 kj/ (kg K)) can b aud to b contant. Fnd: (a) Sktch th xr (opn yt or control volu) to b ud for part (b) and (c); (b) Calculat th hat tranfr (kw) fro th xr to th urroundng nvronnt; (c) valuat th total ntropy producton rat n kw/k: (c1) for th xr bcau of th xng proc and (c) for th nvronnt bcau of th hat tranfr calculatd n part (b); Aupton: (1) Stady Stat, Stady Flow () Nglct K, P (3) No work don othr than flow work Bac quaton: d = ɺ ɺ d = ɺ ɺ V V Q + ɺ + + ɺ W ( h gz ) ( h + + gz ) H,L B,S ɺ Q = + ɺ σ + ɺ ɺ H,L (a) Syt ktch: 1.5 kg/ 1 = 700 K P1 = bar Q 3 kg/ 3=500 K P3=1 bar 1.5 kg/ = 300 K P =1.5 bar ~4~

6 Soluton: (b) Hat lo fro th xr d = ɺ ɺ ɺ + ɺ = ɺ 1 3 d = ɺ ɺ V V Q + ɺ + + ɺ + + ɺ + ɺ + ɺ = ɺ W ( h gz ) ( h gz ) QH h h h H,L B,S Q ɺ = 3( )( 500 ) 1. 5( )( 700 ) 1. 5( )( 300 ) = 0kJ / H (b) 0 kw (c) ntropy producton rat (Mxr) = + ɺ σ + ɺ ɺ ɺ σ = ( ɺ + ɺ ) ɺ ɺ ɺ σ H,L = 1. 5( c ln( / ) R ln( p / p )) ( c ln( / ) Rln( p / p )) p p = 1. 5( ln( 500 / 300 ) ln( 1 / 1. 5 ) ( ln( 500 / 700 ) ln( 1 / ) = = kw / K (c1) kw/k (c) ntropy producton rat (Surroundng) ɺ σ Surroundng = + ɺ σ + ɺ ɺ H,L Q = ɺ = 0 (c) 0 kw/k nflow and outflow bad ntropy producton agnd to xr and o not condrd n th urroundng vn though a broad dfnton of th urroundng could nclud t whr th nflow orgnat and outflow fnh. f th tr ar not xplctly xcludd hr, thy wll b doubl countd n vw of (b) abov whn accountng for ntropy producton rat of th unvr. ~5~

ME 300 Exam 1 October 9, :30 p.m. to 7:30 p.m.

ME 300 Exam 1 October 9, :30 p.m. to 7:30 p.m. CIRCLE YOUR LECTURE BELOW: First Na Last Na 10:0 a.. 1:0 p.. Naik Gor ME 00 Exa 1 Octobr 9, 014 6:0 p.. to 7:0 p.. INSTRUCTIONS 1. This is a closd book and closd nots xaination. You ar providd with an