Pressure Formula:
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Definition: The Peng-Robinson equation is a thermodynamic equation of state that provides accurate predictions of the behavior of real gases.
Purpose: It's widely used in chemical engineering and thermodynamics to calculate properties of pure components and mixtures.
The calculator uses the Peng-Robinson equation:
Where:
Details: This equation provides more accurate predictions of vapor pressures and liquid densities than simpler equations of state, especially near the critical point.
Tips: Enter all required parameters. Reduced parameters are dimensionless ratios (actual value/critical value). Critical parameters are substance-specific properties.
Q1: What are typical values for a and b parameters?
A: These vary by substance. For example, for water: a ≈ 0.5536 Pa·m⁶/mol², b ≈ 3.049×10⁻⁵ m³/mol.
Q2: How is the α-function determined?
A: It's typically a function of temperature and acentric factor, often calculated as α = [1 + κ(1 - √(T_r))]² where κ is substance-specific.
Q3: When is this equation most useful?
A: For calculating properties of non-polar or slightly polar fluids at conditions near or above critical point.
Q4: What are reduced properties?
A: Reduced properties are dimensionless ratios of actual properties to critical properties (e.g., T_r = T/T_c).
Q5: How accurate is this equation?
A: Typically within 1-2% for vapor pressures and 2-5% for liquid densities for many substances.