Question

A mass of 1 kg of air contained in a cylinder at 1.5 MPa, 1000 K, expands in a reversible adiabatic process to 100 kPa. Calculate the final temperature and the work done during the process, using

a. Constant specific heat, value

b. The ideal gas tables,

Answer 1

C.V. Air.

Continuity Eq. m2 = m1 = m ;

Energy Eq. m(u2 − u1) = 1Q2 − 1W2

Entropy Eq m(s2 − s1) = ∫ dQ/T + 1S2 gen

Process: 1Q2 = 0, 1S2 gen = 0 => s2 = s1

(a) Using constant Cp gives the power relation

(b) Use the standard entropy function that includes variable heat capacity