Peng-Robinson Parameter a Formula:
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Definition: Peng-Robinson parameter 'a' is an empirical parameter characteristic to the equation obtained from the Peng-Robinson model of real gas.
Purpose: It's used in the Peng-Robinson equation of state to better predict the behavior of real gases, especially near the critical point.
The calculator uses the formula:
Where:
Details: The 'a' parameter accounts for intermolecular attractive forces in real gases. Accurate calculation is essential for precise thermodynamic modeling.
Tips: Enter all required parameters. Default α-function value is 2, but this may vary based on temperature and substance. All values must be positive.
Q1: What are typical values for critical temperature and pressure?
A: These vary by substance. For water: Tc = 647 K, Pc = 22.06 MPa. For methane: Tc = 190.6 K, Pc = 4.59 MPa.
Q2: How do I determine reduced parameters?
A: Reduced parameters are actual values divided by critical values (e.g., Tr = T/Tc).
Q3: What's the significance of the α-function?
A: The α-function accounts for temperature dependence of the attractive term in the equation of state.
Q4: How does this differ from van der Waals parameter a?
A: Peng-Robinson 'a' is temperature-dependent and generally provides better accuracy, especially for polar molecules.
Q5: What units should I use for consistency?
A: Use SI units: K for temperature, Pa for pressure, m³/mol for volume.