Reduced Pressure of Real Gas using Reduced Wohl Equation given Reduced Parameters Calculator

Formula Used:

\[ P_r = \frac{15T_r}{4(V'_r - \frac{1}{4})} - \frac{6}{T_r V'_r (V'_r - \frac{1}{4})} + \frac{4}{T_r^2 V'_r^3} \]

Reduced Pressure (P_r):

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1. What is Reduced Pressure in Wohl Equation?

Definition: Reduced pressure is the ratio of the actual pressure of a fluid to its critical pressure. It's a dimensionless quantity used in corresponding states theory.

Purpose: This calculator determines the reduced pressure of a real gas using the Wohl equation with reduced temperature and reduced molar volume as inputs.

2. How Does the Calculator Work?

The calculator uses the Wohl equation in reduced form:

\[ P_r = \frac{15T_r}{4(V'_r - \frac{1}{4})} - \frac{6}{T_r V'_r (V'_r - \frac{1}{4})} + \frac{4}{T_r^2 V'_r^3} \]

Where:

\( P_r \) — Reduced pressure (dimensionless)
\( T_r \) — Reduced temperature (dimensionless)
\( V'_r \) — Reduced molar volume (dimensionless)

Explanation: The equation accounts for deviations from ideal gas behavior through three terms that consider different molecular interactions.

3. Importance of Reduced Parameters

Details: Using reduced parameters allows for generalized calculations that can be applied to many substances when their critical properties are known.

4. Using the Calculator

Tips:

Enter reduced temperature (typically between 0 and 10)
Enter reduced molar volume (must be greater than 0.25)
All values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What is the range of valid inputs?
A: Reduced temperature must be > 0, and reduced molar volume must be > 0.25 to avoid division by zero.

Q2: How do I obtain reduced temperature and volume?
A: Reduced temperature = T/T_c, Reduced volume = V/V_c, where T_c and V_c are critical properties.

Q3: Why does the equation have three terms?
A: The terms account for different molecular interactions: the first for repulsive forces, the second for attractive forces, and the third for polar interactions.

Q4: When is the Wohl equation most accurate?
A: It works best for simple, non-polar molecules at moderate pressures and temperatures.

Q5: What are typical values for reduced pressure?
A: Most systems operate with P_r between 0 and 10, though values can be higher in special cases.