Departet of echacal Egeerg E 322 echacal Egeerg Therodyacs Ideal Gas xtures Lecture 31
xtures Egeerg Applcatos atural gas ethae, ethae, propae, butae, troge, hydroge, carbo doxde, ad others Refrgerats Zeotropes - True xture behavor Exaple: R407c - R32/125/134a (23/25/52 by ass) Azeotropes - xtures that behave as a pure flud Exaple: R507A - R125/143a (50/50 by ass) Ar ad ater vapor Psychroetrc aalyss Ar codtog applcatos 2
P [psa] P [psa] Pure Flud vs. xture Behavor 10 3 R22 10 3 R407C 150 F 200 F 150 F 100 F 100 F 200 F 10 2 50 F 10 2 50 F 0 F 0 F -50 F 10 1 60 80 100 120 140 160 180 200 220 h [Btu/lb] R22: a pure flud; a halogeated ethae olecule (chlorodflouroethae) -50 F 10 1 8x10 0-20 0 20 40 60 80 100 120 140 160 h [Btu/lb] R407C: a xture of R32, R125, ad R134a 3
Therodyac Propertes of xtures Real xture behavor Real xture odel Very coplex to descrbe aalytcally Topc for a advaced course EES ca calculate real-propertes of coo xtures! Lo-pressure, oderate desty Ideal soluto odel Gases are treated as real fluds th dealzed xg Topc for a advaced course Lo-pressure, lo desty Ideal gas xg odel Gases are treated as deal gases th dealzed xg E 322!! 4
Ideal Gas xture odels Eve though the deal gas xg odel s splfed, t turs out to be farly accurate for to portat processes that echacal egeers deal th... Ar Codtog Water vapor + ar xtures Codtos are sutable for deal gas property estato eve for ater vapor! Cobusto Aalyss Products of cobusto are ofte at hgh teperatures ad lo pressure The rest of E 322 deals th these to processes 5
A Exaple Gas Turbes Ar to the cobusto chaber Products of cobusto leavg the cobusto chaber Cobusto products ca cota CO 2, H 2 O, O 2, 2, CO, O 2, ad others! I order to get a better estate of the perforace of the gas turbe, e eed to be able to detere the propertes of the xture passg through the turbe 6
Propertes of Ideal Gas xtures Cosder ay property, B (extesve) or b (tesve). For a xture, ass Bass* olar Bass B B b 1 1 b B b b 1 1 ass fracto *Other coo ords: eght bass or gravetrc bass B B b 1 1 b B b y b 1 1 y ole fracto** **ote: The text uses c for ole fractos 7
ass/ole Fracto Coverso 8 I soe staces, a coverso betee ass fracto ad ole fracto s eeded. The ass of a substace s related to the uber of oles through the olecular ass,, Cosderg the ass fracto, y y
ass/ole Fracto Coverso 9 A slar aalyss for the ole fracto reveals, y Suary of fdgs... y y / / y 1 1 / /
Exaple Gve: A xture of deal gases has the follog olar coposto; Argo (y Ar = 0.20), helu (y He = 0.54), ad the balace s carbo ooxde. Fd: (a) ole fracto of carbo ooxde (b) the olecular ass of the xture (c) the gravetrc (ass) coposto of the xture ote: The olecular ass of the xture ca be foud by, 1 1 y 10
Exaple The ole fractos of the argo ad helu are gve. Therefore, the ole fracto of carbo ooxde ca be foud, y y y y Ar He CO 1 1 y 1 y 1 y y 10.20 0.54 0.26 CO Ar He o, the olecular ass of the xture ca be foud, y y y y Ar Ar He He CO CO lb lb lb lb 0.2039.94 0.54 4.003 0.26 28.01 17.43 lbol lbol lbol lbol Table C.13a Table C.13a Table C.13a 11
Exaple The ass fracto coposto of the xture ca be foud by, Therefore, Ar lb y y 0.20 39.94 lbol Table C.13a 0.458 lb 17.43 lbol He y 0.54 4.003 lbol Table C.13a 0.124 lb 17.43 lbol lb CO lb 0.26 28.01 lbol Table C.13a 0.418 lb 17.43 lbol 12
Exaple Coparso of ole fractos ad ass fractos for ths xture... Copoet y Ar 0.20 0.458 He 0.54 0.124 CO 0.26 0.418 1.00 1.00 It s alays a good dea to chec f the calculated fractos su up to oe! 13
Ideal Gas xture Propertes We have prevously see that, b b or b y b Cosder the teral eergy ad ethalpy of a deal gas xture. The copoets of the xture exst at the sae teperature as the xture. Therefore, accordg to the expressos above, or u T u T u y u T T T or h T h T h y h T T T 14
Aother Exaple Gve: A xture of deal gases s cotaed a closed, rgd cotaer that has a volue of 2 ft 3. The xture s a equolar bary xture of ethae ad ethae. The xture s tally at 15 psa, 20 F. Heat s o trasferred to the xture pressure ad teperature becoe 60 psa, 300 F. T T 20F P 15 psa 300F P 60 psa 1 1 2 2 V 3 2 ft Q 12 Fd: The aout of heat trasferred ths process. 15