# Rankine Cycle

 The flashcards below were created by user KatieMac on FreezingBlue Flashcards. Rankine Cycle Ideal cycle for vapor power plants Process 1-2 isentropic compression in a pump process 2-3 constant pressure heat addition in a boiler process 3-4 isentropic expansion in a turbine process 4-1 constant pressure heat rejection in a condenser internal irreversibilities? NO! Pump enters as - saturated liquidduring: compressed isentropically; T increases, brought to operating pressure of boilerleaves as - compressed liquid boiler enters as - compressed liquidduring: heat exchanger, T increase, no P changeleaves as - superheated vapor turbine enters as - superheated vaporduring - expands isentropically; T and P dropleaves as - saturated liquid-vapor mix condenser enters as - saturated liquid-vapor mixduring - Heat exchanger, reject heat to cooling medium, no P change dropleaves as - saturated liquid steady-flow energy equation (qin-qout) + (win-wout) = he-hi simple - Pump eq. (q=0)wpump,in=h2-h1 = v(P2-P1)h1=hf@P1 and v=v1=vf@p1 simple - boiler eq. (w = 0)qin=h3-h2 simple - turbine eq (q=0)wturb,out = h3-h4 simple - condenser eq (w=0)qout=h4-h1 thermal efficiency nth=wnet/qin =1 - qout/qin wnet wnet = qin-qout=wturb,out-wpump,in simple - state 1 saturated liquidFind h and v - given P, look @ Table A-5 (saturated water) simple - state 2 compressed liquidFind h - apply conservation of energy eq. simple - state 2 cons. of energy equation wpump,in = wturb,outh2-h1=v(P2-P1)h2 = v(P2-P1)+h1 simple - state 3 superheated vaporFind h and s - given T and P, look @ Table A-6 (superheated water) simple - state 4 saturated liquid-vapor mixFind h - given P; apply quality equationsget values from A-5 quality equations x# = x# - sf / sfgh# = hf+x#hfgh# = hf + (s# - sf / sfg)hfg wturb,out w/ efficiency wturb,out = ntws turb,out wpump,in w/ efficiency wpump,in = ws, pump in / np linear interpolate y = y0 + (x-x0)(y1-y0 / x1-x0)x - given0 and 1; table #'s double linear interpolate Using ex. from hw1) Btwn two P's, linear interpolation for each T, get ha and hb2) Btwn two T's, linear interpolate with ha and hb for final h net power W*dot*net = (mass flow rate)Wnet Increase efficiency increase T for superheated steamincrease boiler pressure, at same T (but quality decreases)decrease T heat is rejected from condenser reheat rankine cycle two stage turbine to solve excessive moisture problem after increasing boiler pressure reheat - qin qin = qprimary + qreheat = (h3-h2) + (h5-h4) reheat - wturb,out wturb,out = wturb,I + wturb,II = (h3-h4)+(h5-h6) Preheat = P5 = P4 Find Preheat T3 = T5 - to maintain heatfind entropy at state 6 - s6 = sf + x6sfguse T5 and s5/6 , look @ Table A-6 to find P reheat - state 1 saturated liquidfind h and v = given P, look @ table A-5 reheat - state 2 compressed liquidapply conservation of energy eq. (use h1 and v1) reheat - state 3 superheated vaporfind h3 and s3, given P and T look @ Table A-6 reheat - state 4 saturated liquid-vapor mixCalculate P4, s4 (s3)Look @ Table A-6 reheat- state 5 Superheated vaporGiven T and s5(s4), look @ Table A-6 reheat - state 6 Saturated mixtureGiven P, look @ A-5apply quality equations, h6 = hf + x6hfg Ideal Regen. Rankine cycle w/ open FWH FHW - device that heats feedwater by regeneration regeneration transfer heat to the feedwater from the expanding steam, in counterflow exchanger built into the turbine FWH - qin qin = h5-h4 FWH - qout qout = (1-y)(h7-h1) FWH - wturb,out wturb,out = (h5-h6) + (1-y)(h6-h7) FWH - wpump,in wpump,in = (1-y)wpumpI,in + wpumpII,in fraction of heat extracted y = m6/m5 (mass flow) = h3-h2 / h6-h2 FWH - state 1 saturated liquidFind h and v - given P, look @ Table A-5 FWH - state 2 compressed liquidapply conservation energyFind h FWH - state 3 saturated liquidfind h and v, given P (same as 2 and 6), look @ Table A-5 FWH - state 4 compressed liquidapply conservation energyfind h FWH - state 5 superheated vaporfind h and s, given P and T, look @ Table A-6 FWH - state 6 saturated liquid-vapor mixfind h, given P, apply quality equation FWH - state 7 saturated liquid-vapor mixfind h, given P appy quality equation AuthorKatieMac ID10842 Card SetRankine Cycle DescriptionChemical Thermodynamics Updated2010-03-17T09:14:41Z Show Answers