University:
The Pennsylvania State University
Course:
CHE 220 | Introduction to Chemical Engineering Thermodynamics
Academic year:

2020
Views:

47

Pages:

9
Author:

study_genius

Topics for Reading : * Heat capacities * Heat of * Const P 3.5 - 3.7 Today ,G 4 Cv vaporisation process with phase change Elementary Constant * Paths const Volume Process W oh Q+ w=ypµr0=o} °u=Q For Constant * . Volume Pressure Constant DU = heating : Qtw w¥Pdv= For constant Pressure . p Heating : #: T T Q=0U Process .o✓] \ . Q=oU+Po✓=oµ Q=oH . ✓ Heat + Definition of Cp cp= const : ( 3¥)p heat P . Capacities capacity = : heat change capacity . Cv=( ¥ )v amountofheat@cont.V = : , ÷ temperature change amountofheat@cmsT.Ptemp.c4gngehophaseXDetinitionofcviamst.V Immediate consequence anstv process of these definitions Q=¥TudT : IT bhofgudt , The const .P Q=§?g>dT oHiz¥,cpdT , process Bothqantcvdepemdonidp . For liquids , theeftetotpis very small . . nd 1bar Solution From 20°C , . Definition of Cp : Tables Steam @ 70bar H ,= Ti=37 's : × 3090.4 Note : DT has the same valu eintantink -12=400 5=450 1+2=3159.1 EXampU1Usethesteam-abbstoca1w1atetheCpotwator@7Obar.400oC.a op.co#DptH*@sami~x H# zzggzf Hz= Cpc or or q ,~ . Cpc Hz H } - . # ,= 2.748¥gk Hz = HjyH÷= 2.5821¥ 8 2.637 KJIKGK ! 1bar Solution From 20°C , . Definition of Cp : 9 : " ( ¥T ) "=&¥)@" Takesfrsatnianie ~×µµ ¥6 steam MP : T=l6°C Hit T2= 20°C HZ H3I 67.17 " 83.92 24°C 100.66 Tz -240C Exampllt.Usethesteam-abbstoca1w1atetheCpotwator@70baY400oC.an CPI or Or #= HZH Cpc 4.1875K¥ #z= H3 Hz - Cpa , Hs H , - #= c 4.18541g 4186k¥ K .k Example 2 : Jlmdk yk a Aatcnlisheated@anHantR1barfrm2Okto40k.CaklateOybH.DU Attritional 135.6 = , p= Solution >T+ an ' p 2.837 = kglm 791 3 MW at =§ta+bT+cT3tkT= kslmol = Thtbfi Tilts ftp.T.3 ) - . 58.08×153 DUN H If Attn = - PV - BDV Vi = Vz= A . 6.48×503 ki Q=oHz=§÷pdT h= .io#6.89.io7T3 =L g into . . My 0 ( pv ) ,z= OHR - P . Dkz Krol change . k¢Y pkY=§pdT 1uV÷=kE = , . T, due PDVn= 01 0Uh=DHizPDk2= 2543.78 Jlmol . . . . . to ) Vz=V 73426.10-5 MYKG 8.359.155 hhlkg 2544.8 = Hmo , Jlmol heating , Ekth 'T ' ' . During added heat the phase chance goes HeatofVaporitatimHea-ofvapontntim.0HraPOqA@0Hrap-Hv-Hu.X the but does not convert into , liquid change heat heat Latent * The Go For : change For example , . causes : causes in change a Temperature change phase a only for heating / cooling used be can phase vapor ( vapor temperature Sensible to use for HP an 2¥ Dltrap no , with change phase no heating from AT = compressed liquid Tz Jcpldt IT g heat capacity of + Okapi f + liquid change . . . state Q temperature in heat of SAT dt 1- capahity vapor of ( state 1) to superheated Mean Cp Cp is generally The a btw Cp mean function of I T go : defined is Tz & got = ) as : Tz Ep ¥dT = Tz If the go is known mean OH However each for , 2 : el I ( cm 0h12 't 'd = Ep ( Tz we - can change . . The mean - T, ) write ) I the calculations Tz ) , Tz 5kd,o§;do÷= cI= Then Tp ( = T then , accurate time Example he - mean ( be recalculated . got acetone 252440.8=127.4 = must Cp 127.4 mtg , ,c btw 20°C ¢ 40°C is Hmotk ) ( 40 -24°C = 2544.8£ , , Sources for oltrap Tables * ( e.g. steam Empirical Equations 0,2kt * Note : At = the of Sat big . tables ) . : 7.084-7935+4 critical point converge to 10 . wa -75656 bk the as oHvap=o those of Sat . vapor properties .