Efficiency of Carnot Cycle with Arbitrary Gas Equation of State
  The derivation of the efficiency of Carnot cycle is usually done by calculating the heats involved in two isothermal processes and making use of the associated adiabatic relation for a given working substance's equation of state, usually the ideal gas. We present a derivation of Carnot efficiency using the same procedure with Redlich-Kwong gas as working substance to answer the calculation difficulties raised by Agrawal and Menon. We also show that using the same procedure, the Carnot efficiency may be derived regardless of the functional form of the gas equation of state. 
Paulus C. Tjiang, Sylvia H. Sutanto