Thermo EQs - Aftercooler Boiler Condenser Combustor...

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Unformatted text preview: Aftercooler Boiler Condenser Combustor Compressor Deaerator Dehumidifier Desuperheater Diffuser Economizer Evaporator Expander Fan/blower Feedwater heater Flash evaporator Heat engine Heat exchanger Heat pump Heater Humidifier lntercooler Nozzle Mixing chamber Pump Reactor Regenerator Steam generator Supercharger Superheater Turbine Turbocharger Throttle Valve Cool a flow after a compressor Bring substance to a vapor state Take 9* out to bring substance to liquid state Burn fuel; acts like heat transfer in Bring a substance to higher pressure Remove gases dissolved in liquids Remove water from air Add liquid water to superheated vapor steam to make it saturated vapor Convert KE energy to higher P Low-T, low—P heat exchanger Bring a substance to vapor state Similar to a turbine, but may have a q Move a substance, typically air Heat liquid water with another flow Generate vapor by expansion (throttling) A device that converts part of heat into work Transfer heat from one medium to another A device moving a Q from TN to Thigh, requires a work input, refrigerator Heat a substanCe Add water to airw—water mixture Heat exchanger between compressor stages Create KE; P drops Measure flow rate Mix two or more flows Same as compressor, but handles liquid Allow reaction between two or more substances Usualiy a heat exchanger to recover energy Same as boiler, heat iiquid water to superheat vapor A compressor driven by engine shaft work to drive air into an automotive engine A heat exchanger that brings T up over T3,,at Create shaft work from high P flow A compressor driven by an exhaust flow turbine to charge air into an engine Same as valve Control flow by restriction; P drops Given w=0 w=0 w=0 w=0 win w=0 w==0 w=0 w=0 w=0 wrn,KEup w=0 w=0 qin,wout l*’=0 win w=0 w=0 w=0 w=0 w=0 win,Pup w==0 w=0 w=0 win w=0 wout WmmineWWCV w=0 Assumption P = constant P = constant P = constant P = constant 9 = 0 P = constant P = constant P = constant q = 0 P = constant P = constant P = C, q z 0 P : constant :3 = 0 P = constant P = constant P = constant P = constant q = 0 P = constant 4 = 0 Rate equation for entropy Entropy equation Total entropy change Lost work Actual boundary work Gibbs relations Solids, Liquids Change in 3 Ideal Gas Standard entropy Change in 5 Ratio of specific heats Polyttopic processes Specific work. tW2=deV_ Wins: Ttis=du+Pdv Tds=dh~vdP dv=0 _ _ @_ an; E .32 Chi-T} v = constant, T (Function of T) To P s2 3. = 3?" s21 —~ R In F2 (Using Table A? or A.8) 1 T P S2 - .s'; = C1,,0 in ? R111 172 (For constant Cp, CU) 1 1 Tz 1)2 52 s, a CD in? + R In 0—] (For constant Cp, C”) l k = CPD/C00 PU" = constant; PV” = constant flzfln=fln=§njl P1 1/2 v2 r. 1w2:l*n(P2l-}2 Plvl)=lwn(T2_‘Tl) 71*] v P ,w2=P1vllnv—?=Rflln;%=RTlln~i n=1 The work is moving boundary work w = f P do _ v” .Wma-MMWWM... entifiable processes 11 = 0; P = constant; lsobaric n l; T = constant; Isothermal n —- k; s = constant; Isentropic v = constant; Isochoric or isometric MWnM'u-nrm . (All W, Q can also be rates Q) Heat engine Heat pump Refrigerator Factors that make processes irreversible Carnot cycle Proposition 1 Proposition II Absolute temperature Real heat engine Real heat pump Real refrigerator Heat—transfer rates Flow irreversibility Reversible work C.M. Irreversibility C.M. Second-law efficiency Exergy, flow availability Exergy, stored Exergy transfer by heat Exergy transfer by flow Exergy rate Eq. Exergy Eq, CM. W 0 WHE =QH—QL; 71H}: :Q—ZE:1_§—; WHP ZQI-I—QL; 3H1) =7§izfi _ Qt. _ QL WREF 2 QH — QL; finer — WREF " m Friction, unrestrained expansion (W = 0), Q over AT, mixing, current through a resistor, combustion, or valve flow (throttle). 1—2 Isothermal heat addition Q” in at T” 2—3 Adiabatic expansion process Tdoes down 3—4 Isothermal heat rejection QL out at T L 4—1 Adiabatic compression process T goes up "any S nmvcrsible same TH: TL "Carnot 1 = "Camotz same TH» TI. 35 : e TH T 77m; = Q—fs nCamotHE =1" 7T; QH T1 BHP — W—HP S BCamotl—l? = TH _: TL ., T BREF = WklEF S BCnmot REF = TH _L TL 9 = CAT i= w'e" — w = q?" = ToSge r52 = Tosgen T IWECV = T0032 _ SI) — (U2 .— Ul) + IQZ — T 112 = T00} _ Si) — inTI: = TOISchn 77an law '— Cbgnincd __ (bsupplied _ d>destroyed «supplied damned w= [h- Tos+%V2+ng—[ho—Toso+gzol 2 <75 = (e —- e0) + P00) — v0) — T0(s — so); (I) = m To qbtransfer = q 1 — TH d’transfcr = htot I _ him e _ T0(Si _ Se) "d_t'_ Qc.v. Wow. +P0 dt + 2 mil/Ii — 2 rhe¢e — Taggen 'WM Mu. :MWp—u,mcummmifl‘mmm Wh‘lmgfin‘flfifig‘fimmmxmm\=rdmmhmwwmnmmguwmm m.w-.. Volume flow rate I" = [V dA = AV (using average velocity) Mass flow rate ti; = fp V tiA = pAV = A‘Wv (using average values) Flow work rate Wflow = PV = :7?th Flow direction From higher P to lower P unless significant KB or PE. Instantaneous Process Continuity equation the» = 2 132‘- - 2 rite Energy equation EC“ = QC“ - WCN. + 2 rig-km ,. - 2 mam TOtal hm: = h + %V2 + = hsmgnation + Steady State No storage: 152C.“ = 0; EC_V_ == 0 Continuity equation 2 :52; = 2 rite (in = out) Energy equation ch. + 2 mshmu 2 av. + E Iiichum: (in = 0110 Specific heat transfer q = gay/2;: (steady state only) Specific work w = Wc‘v‘hiz (steady state only) Steady-state single flow q + km 1 = w + hm L, (in = out) energy equation Transient Process Continuity equation m2 — m1 = E m: — 2 me Energy equation E2 '" E! = 1Q2 “ {W2 + E mr'hlotf _ 2 mehtote 1 1 E2 '“ El = "12(“2 + EVE + 822) _ "110*! + 3"? + 8'21) 1 hm: e : blot exit average 3 E (hllot el + htot :32) W w M...”— WW" t-H-Iwh—um—‘Wl—W m..- -—--—u--._-......_-... up“..- .m.mm.muw_——wwm"——wm—MW .an Total energy E = U + KE + KB = mu + 1» mV2 + ng 2 Kinetic energy KE = %m"lf2 Potential energy KE = ng Specific energy e = u + % ‘II2 + gZ Enthalpy h *=‘ u + PU Two-phase mass average at = uf + xufg = (1 - x)uf + 3mg )2 = hf+ mfg = (1 — x)hf+ xhg . . =’ 15:25 . z 212 SpeCIfie heat, heat capaelty Cu (M1)”: Cp (3T1) Solids and liquids Incompressible, so u = constant “=" of and v very small C = CU = CF, [Tables A3 and AA (F2 and F.3)] “2 " “I = 002 F T1) hz — h, = 242 - u} + 00’: - Pl) (Often the second term is small.) 11 = hf+ vf (P — Pm); u E a; (saturated at same .7) Ideal gas I: = u + Pv = u + RT (only functions of I) -"-' fl' = fl : Cu — dT,CP dT Cu+ R M2 _ “1=JCudT§ Cv(T2 "' Tl) h2 - h, = [ders (3,,(23 —— T.) Left—hand side from Table A7 or A.8, middle from Table A.6 and right-hand side from Table A.6 at a TM or from Table A5 at 25°C Lefi-hand side from Table F.5 or R6, right—hand side from TableFA at 77 F Energy equation rate form E = Q — W (rate = + in - out) Energy equation integrated £2 —* E, = lQ2 — .Wz (change = + in — out) I 5 MOVE — Vi) + mg(Zz “ Zn) Multiple masses, states E = mAeA + 271363 + mc ac + - - - "1(92 ‘ 91) = "3(“2 — “1) + :u- um-u—awwummmmmnw mtmmmmmn‘nn—n m wax mmqmme-‘W7de—memmmmu Rate equation for entropy rate of change = + in — out + generation SW = 2 131,3,- — 2 153953 + E Q?“ + Sam 5L“:- e 5 Steady state single flow 59 = s,r + ~13 + 336,, Reversible shaft work w = --f U dP + — %V§ + gZi — ch, i Reversible heat transfer q : Tds = he. — h,- — v dP (from Gibbs relation) Bernoulli equation v0”i m P6) + % V? — %V§ + ng — ch, = 0 (v = constant) Polytropic process work w = —n f 1 (Pene — Pivi) = —nn_Rl (Te - T!) :2 # I _ _ P8 _ _ Pa _ ve _ w— Pivilnpiw REInPE—RTilnE 11—] E The work is shaft work w = - I v dP and for ideal gas Isentropic efficiencies 17mm = who/W73 (Turbine work is out) momma, = Wag/WC“ (Compressor work is in) 71me = WP5/Wpac (Pump work is in) “name = A %V§c/A % V3 (Kinetic energy is out) - - - MAW ummmumm w r m mammmmmmmmmwmmwmwanmumwwmmwwnmmwmmmwm: mam)“ M. w 43573:."wa . W T Available work from heat W = Q (I _ 5T3) H Reversible flow work with extra q?" T from ambient at T0 and q in at TH 936V : T0698 in Si) b q 7:9” H To WICVEhimhemTo(s.-mse)+q 1“? H Rankine Cycle Open feedwater heater Closed feedwater heater Deaerating FWH Cogeneration Brayton Cycle Compression ratio Regenerator Intercooler Jet engine Thrust Propulsive power Feedwater mixed with extraction steam, exit as saturated liquid Feedwater heated by extraction steam, no mixing Open feedwater heater operating at Pm to vent gas out Turbine power is cogenerated with a desired steam supply Pressure ratio rp = Phigh/Plow Dual fluid heat exchanger, uses exhaust flow energy Cooler between compressor stages, reduces work input No shaftwork out, kinetic energy generated in exit nozzle E = 152(Ve — Vi) momentum equation W = F Vaircrafi x _ vi)vaircrafi Piston Cylinder Power Cycles Compression ratio Displacement (1 cyl.) Stroke Mean effective pressure Power by I cylinder Refrigeration Cycle Coefficient of performance Combined Cycles Topping, bottoming cycle Cascade system Volume ratio rv = CR = V / V max min AV “— Vmax — ‘Vmin 1—" mfijmax — Umin) : SAcyl S — 2 Rm, piston travel in compression or expansion. Pmeff m wnet/ vmax u Umin) 2 Wnet/(Vmax "— Vmin) _ RPM - W — mwm ——6—6— (times% for four-stroke cycle) The high- and low-temperature cycles Stacked refrigeration cycles Phases Phase equilibrium Multiphase boundaries Equilibrium state Quality Average specific volume Equilibrium surface Ideal—gas law Universal gas constant Gas constant Compressibility factor Z Reduced properties Equations of state Work Heat Displacement work Specific work Power, rate of work Polytropic process Polytropic process work Conduction heat transfer Conductivity Convection heat transfer Convection coefficient Radiation heat transfer (net to ambient) Rate integration Solid, liquid, and vapor (gas) Tsar» Psat: Ufi Ug? vi Vaporization, sublimation, and fiision lines: Figs. 3.5 (general), 3.6 (C02) and 3.7 (water) Critical point: Table 3.1, Table A2 (F .1) Triple point: Table 3.2 Two independent properties (#1, #2) x = mvap/m (vapor mass fraction) 1. — x = mnq/m (liquid mass fraction) 0 = (1 — 2c)vJ,r + xvg (only two—phase mixture) P—U—T Tables or equation of state 5v = RT PV= mRT = nRT R = §3145 kJ/krnol K R = R/M kJ/kg K, Table A5 or M from Table A2 it lbf/lbrn R, Table F4 or M from Table El PD 3 ZRT Chart for Zin Fig. D.l P,. = 3 T, = I Entry to compressibility chart PC Tc Cubic, pressure explicit: Appendix D, Table D.l B»W~.R: Eq. 3.7 and Table 13.2 for various substances Lee Kesler: Appendix D, Table D3, and Fig. D.l Energy in transfer—mechanical, electrical, and chemical Energy in transfer, caused by a AT 2 2 2 2 W=der=deV=fffdA=de8 1 l 1 1 mg = W/m (work per unit mass) W = F V = PV = Tm (V displacement rate) Velocity V = rm, torque T = Fr, angular velocity 2 a) PV" 2 constant or Pv" = constant 1 [W231MH(P2V2”PIVI) V .W, = PIV, In}; (ifn =1) l ' _ ._ if Q — kA (ix It; (W/m K) Q = 11A AT h_(W/m2 K) Q = eel-AU: — Tgmb) (0' = 5.67 x 10*8 W/m2 K4) 1Q2 : [ th ” Qavg A1 ...
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Thermo EQs - Aftercooler Boiler Condenser Combustor...

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