1. ENGR 2213 Thermodynamics F. C. Lai School of Aerospace and Mechanical
Engineering
University of Oklahoma

2. Enthalpy H = U + pV h = u + pv dh = du + p dv + v dp du = q - w
q = du + w
= du + p dv
= dh – v dp
For an ideal gas undergoes a constant pressure
process,
cp specific heat at constant
pressure
cp = cp (T)

3. Enthalpy h = u + pv = u + RT cp = cv + R
k = cp / cv specific heat ratio

4. Enthalpy For compressed liquids, v ~ vf u ~ uf h = u + pv ~ uf + pvf
~ uf + psatvf + pvf – psatvf
~ hf + vf (p – psat)

5. Polytropic Process of an Ideal Gas
pVn = constant
n ≠ 1
n = 1

6. Polytropic Process of an Ideal Gas
pVn = constant
(pV)Vn-1 = constant
(mRT)Vn-1 = constant
TVn-1 = constant
T1V1n-1 = T2V2n-1 = constant

7. Polytropic Process of an Ideal Gas
pVn = constant
(pV)np1-n = constant
(mRT)np1-n = constant
Tnp1-n = constant
T1np11-n = T2np21-n = constant