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 + ₁S_{2 gen} 

Process: ₁Q₂ = 0, ₁S_{2 gen} = 0 => s₂ = s₁ 

(a) Using constant Cp  gives the power relation

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