Peng-Robinson Eqn. of State, Thermo I

In summary, the Peng-Robinson Equation of State is a thermodynamic model used to calculate the properties of fluids, particularly gases and liquids, under various conditions. It combines the van der Waals and Redlich-Kwong equations and is derived from a statistical mechanical approach. However, it has limitations and may not accurately predict the behavior of certain systems. It is commonly used in the oil and gas industry and chemical process design, and there are variations that may be more accurate for specific applications.
  • #1
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Could you please give me a walk through on how to solve for volume of a substance using the Peng-Robinson Equation of State, given:

1. initial and final pressure
2. initial and final temperature (it is an isotherm)
3. it is frictionless (all work is reversible)

P= (RT/V-b)-a(T)/(V(V-b)+b(V-b))
 
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  • #2
You can check out the website and the link below to get an idea how to solve for volume of a substance using the Peng-Robinson Equation of State:

http://eq-comp.com/peng-robinson-cubic-equation-of-state.htm"
 
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  • #3



The Peng-Robinson Equation of State is a thermodynamic model used to describe the behavior of gases and liquids. It is based on the principle of the ideal gas law combined with corrections for non-ideal behavior. In order to solve for the volume of a substance using this equation, we will need to use the given information of initial and final pressure, temperature, and the fact that the process is isothermal and reversible.

Step 1: Write out the Peng-Robinson Equation of State

P= (RT/V-b)-a(T)/(V(V-b)+b(V-b))

Step 2: Substitute the given values into the equation

P= (RT/V-b)-a(T)/(V(V-b)+b(V-b))
P= (RT/V-b)-a(T)/(V(V-b)+b(V-b))
P= (RT/V-b)-a(T)/(V(V-b)+b(V-b))

Step 3: Rearrange the equation to solve for volume (V)

V= (RT/P)+b-(aT)/(P(V-b)+b(V-b))

Step 4: Substitute the initial pressure and temperature values into the equation

V= (RT/P)+b-(aT)/(P(V-b)+b(V-b))
V= (RT1/P1)+b-(aT1)/(P1(V-b)+b(V-b))

Step 5: Solve for the initial volume (V1)

V1= (RT1/P1)+b-(aT1)/(P1(V1-b)+b(V1-b))

Step 6: Use the final pressure and temperature values to solve for the final volume (V2)

V2= (RT2/P2)+b-(aT2)/(P2(V2-b)+b(V2-b))

Step 7: The change in volume (ΔV) can be calculated by subtracting V1 from V2

ΔV = V2 - V1

Step 8: The final volume can be determined by adding the change in volume to the initial volume

Vfinal = V1 + ΔV

Step 9: Substitute the calculated values into the equation to solve for the final volume (Vfinal)

Vfinal = V1 + ΔV
Vfinal = (RT1/P1)+b-(aT1)/(P1(V1-b)+b(V1-b)) + (V2 - V1)

Step 10: Simplify the equation to
 

1. What is the Peng-Robinson Equation of State?

The Peng-Robinson Equation of State is a thermodynamic model used to calculate the properties of fluids, particularly the behavior of gases and liquids under various conditions of pressure, temperature, and volume. It is based on the principle of combining the van der Waals equation with the Redlich-Kwong equation.

2. How is the Peng-Robinson Equation of State derived?

The Peng-Robinson Equation of State is derived from a statistical mechanical approach, using the concept of hard sphere repulsion and attractive forces between molecules. It takes into account the size and shape of molecules, as well as intermolecular interactions, to accurately describe the behavior of real fluids.

3. What are the limitations of the Peng-Robinson Equation of State?

Like all thermodynamic models, the Peng-Robinson Equation of State has its limitations. It is most accurate for small, spherical molecules at moderate pressures and temperatures. It may not accurately predict the behavior of highly non-ideal systems, such as mixtures, polymers, or complex fluids.

4. How is the Peng-Robinson Equation of State used in practice?

The Peng-Robinson Equation of State is commonly used in the oil and gas industry to calculate the properties of hydrocarbons. It is also used in chemical process design, as well as in the development of models for predicting the behavior of mixtures and complex fluids.

5. Are there any variations of the Peng-Robinson Equation of State?

Yes, there are several variations of the Peng-Robinson Equation of State, including modifications to account for specific types of molecules or conditions. Some common variations include the Soave-Redlich-Kwong (SRK) equation and the Patel-Teja equation. These variations may be more accurate for certain applications, but the basic principles of the Peng-Robinson Equation of State remain the same.

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