Question

"Entropy change" negative will? Prove using the relevant equations. (Only verbal answer will not be accepted. It will be proved as thermodynamic calculations under relevant equations). (a) Air isothermally expanded from 6 bar pressure to 3 bar pressure (b) Compressing the air to half its volume at constant pressure (c) constant volume control of air until the pressure is threefold (d) Air expansion isentropically from 6 bar pressure to 3 bar pressure

Answer 1

Vi Sola (9) Griven that process is Isothermal So, If = Ti = T Pga 3 bar Also P ;= 6 bar , Now, pln If Ti AS - 1.005 in T T 0.287 in 3 6 O (-0.1989) 0. 1989 kJ / kg. K AS (6) Griven that process is isobaric . So, Pf a P j = p Also, Vi-V, Vg ald Now, Co In Pf AS2 Cp ln t. 1.005 Xi'an (7) 0.718 In P واسه P AS -0.6966 kJIng. K

le) Isometric 2 Given that So, process is Vj = Vi = V Pipi Pf = 3p Now, AS - Cp ln Vf + Cv lng ASE + 1.005 in v V 0 7 18 in (3p) (p) As= 0.7888 kJ l bg.K (d) P; = 6 bar, Pf = 3 bar Given that process is isentropic: Sf = Si So, AS: 0 Hence, out of all given option, Option (6) has Change" "Negative ". W entropy Completed