ME 200 L26: Entropy Change for an Ideal Gas Kim See’s Office ME Gatewood Wing Room 2172 Please check your HW and Examination Grades on Blackboard Please pick up all graded Home Work ThermoMentor © Program Spring 2014 MWF AM J. P. Gore Gatewood Wing 3166, Office Hours: MWF TAs: Robert Kapaku Dong Han

Recall Ideal Gas, Substitute Entropy Definition into First Law ►Superheated Vapor may be treated as an Ideal Gas if: p/p c 2 ►Property relations derived from mass conservation, first law, and second law apply to all systems when derived from any system.

Entropy S kJ/K or BTU/ o R Change for Ideal Gases ►Remember Chapter 3 (State Principle, Property Relations for p, T, V, v, ρ, U, u, H, h)

Specific Entropy “s” (kJ/kg-K or BTU/lbm- o R) Change for Ideal Gases, Constant c p, c v ►Remember Chapter 3 (Property Relations). Divide by “m” kg

Specific Entropy “s” (kJ/kg-K or BTU/lbm- o R) Change for Ideal Gases, Variable c p, c v ►Remember Chapter 3 (Property Relations). Divide by “m” kg

Entropy Change for Air: Example 0.15 kg of Air at 700 K, 10 atm pressure is heated to 1200 K in a piston cylinder device at constant pressure, find heat added and change in entropy considering variable specific heat and properties from Table A-22. Solution: T, Ku, kJ/kgS o kJ/kg-K

Entropy Change for Ideal Gases: Example 2 lbm of N 2 is heated at constant volume from 32 o F to 70 o F find heat added and change in entropy. Assume: Ideal Gas and variable specific heat with properties given in Table A23E Solution: