Abstract: Isobaric molar heat capacity affected by pressures for non-ideal gases is calculated theoretically at specified temperatures by means of gaseous equations of state, i.e. Redlish-Kwong (RK) Equation, Soave-Redlich-Kwong (SRK) Equation, Peng-Robinson (PR) Equation, Virial Equation, coupled with Romberg numeric integral via solving the key obstacle (∂V/∂T)_p, and integral (∂²V/∂T²)_p. As an example, methane's C_p is calculated at constant 300 K but 1 MPa & 10 MPa. The calculation results show that less than 2% relative errors occur in comparison with literature values at any specified temperatures and pressures if no phase change survives at elevated pressure P₂ and temperature T, or when specified temperatures are greater than critical temperatures in spite of elevated pressures. However, greater errors would be present if gases were considered to be ideal, or if temperatures are lower than critical temperatures at elevated pressures (>10 MPa), because C_p is the function of both temperature and pressure. In particular, elevated pressures have significant effect on C_p.

Key words: Isobaric molar heat capacity, Non-ideal gaseous equation of state, Romberg numeric integral

摘要： Isobaric molar heat capacity affected by pressures for non-ideal gases is calculated theoretically at specified temperatures by means of gaseous equations of state, i.e. Redlish-Kwong (RK) Equation, Soave-Redlich-Kwong (SRK) Equation, Peng-Robinson (PR) Equation, Virial Equation, coupled with Romberg numeric integral via solving the key obstacle (∂V/∂T)_p, and integral (∂²V/∂T²)_p. As an example, methane's C_p is calculated at constant 300 K but 1 MPa & 10 MPa. The calculation results show that less than 2% relative errors occur in comparison with literature values at any specified temperatures and pressures if no phase change survives at elevated pressure P₂ and temperature T, or when specified temperatures are greater than critical temperatures in spite of elevated pressures. However, greater errors would be present if gases were considered to be ideal, or if temperatures are lower than critical temperatures at elevated pressures (>10 MPa), because C_p is the function of both temperature and pressure. In particular, elevated pressures have significant effect on C_p.

关键词: Isobaric molar heat capacity, Non-ideal gaseous equation of state, Romberg numeric integral