The van der Waals pressure calculator computes the pressure of fluid using the van der Waals formula.

INSTRUCTIONS: Choose the preferred units and enter the following:

• (T)  The absolute temperature of the fluid.
• (V_m)  This molar volume.  (The volume is divided by 1 mole)
• (Fluid)  Choose a fluid from the list.

Pressure (P): Pressure is returned in pascals.  However, this can be automatically converted to other pressure units via the pull-down menu.

The Math / Science

This equation computes the pressure of a real fluid.  The van der Waals equation is a state equation based on a the ideal gas law which approximates the behavior of real fluids.

The form of the equation is `p = (R*T)/(V_m-b) - a/V_m^2`, where a and b are look-up values derived from a table specifying these coefficients for a specific selected fluid.

INPUTS:

• T - absolute temperature of the fluid
• `V_m` - molar volume of the fluid ( in `m^3`/mol)
• Fluid - choice of fluid from the list: NH3, Ar, CO2, CI2, C2H6, He, H2, Kr, CH4, Ne, N2, O2, C3H8, SO2, Xe, H2O

Description

The van der Waals coefficients,  a and b, are empirically derived and contribute to the equation being more accurate for real fluids than the Ideal Gas equation . 

This equation looks up the coefficients, a and b from the data set named Van Der Waals Constants.