How to calculate pressure in thermodynamics

In summary, to construct a P vs. T graph using the Peng-Robinson EOS in thermodynamics, start by determining the parameters of the equation, such as A, B, R, Tc, and Pc. Then, set up the temperature range and calculate the reduced temperature (Tr) for each temperature. Next, calculate the reduced pressure (Pr) at each reduced temperature by solving the Peng-Robinson equation. Finally, plot the calculated Pr values against the corresponding Tr values to construct the graph. It is important to note that the specific parameters used may vary depending on the fluid being modeled.
  • #1
JT0532
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How to construct a P vs. T graph using the Peng-Robinson EOS in thermodynamics? The only condition existed is the temperature range from 150 to 520 K. The prof told me that to look for P at a fixed T and then see if the fugacities match, but how exactly can I do it?

The goal is to model the same figure as the attached file.

Please show me some hints since I don't know where i should start. Much appreciated.
 

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  • #2
The first step is to determine the parameters of the Peng-Robinson EOS. Depending on the fluid you are modeling, these parameters will need to be determined through experiments or taken from literature. For this example, we will assume that the fluid is propane and use the following parameters: • A = 0.45724 • B = 0.07780 • R = 0.08206 • Critical Temperature (Tc) = 369.8 K• Critical Pressure (Pc) = 42.48 bar Next, we need to set up the temperature range and calculate the reduced temperature (Tr) for each temperature. The temperature range is 150-520 K and the corresponding Tr values are 0.3987-1.4053 respectively. Then, we need to calculate the reduced pressure (Pr) at each reduced temperature. This can be done by solving the Peng-Robinson equation for a given reduced temperature. Finally, the P vs T graph can be constructed by plotting the calculated Pr values against the corresponding Tr values. I have attached a sample figure which shows a P vs T graph constructed using the Peng-Robinson EOS. I hope this helps!
 

FAQ: How to calculate pressure in thermodynamics

1. How do you calculate pressure in thermodynamics?

The formula for calculating pressure in thermodynamics is P = F/A, where P is pressure, F is force, and A is area. This means that pressure is equal to the amount of force per unit area.

2. What is the SI unit of pressure in thermodynamics?

The SI unit of pressure in thermodynamics is Pascal (Pa), which is equivalent to one Newton per square meter (N/m^2).

3. Can pressure in thermodynamics be negative?

Yes, pressure in thermodynamics can be negative. This occurs when the force acting on a system is in the opposite direction of the area it is acting on.

4. How does temperature affect pressure in thermodynamics?

According to the ideal gas law, pressure and temperature are directly proportional. This means that as temperature increases, pressure also increases, and vice versa.

5. What is the difference between absolute pressure and gauge pressure in thermodynamics?

Absolute pressure is the total pressure exerted by a fluid, including atmospheric pressure. Gauge pressure is the difference between absolute pressure and atmospheric pressure. In other words, gauge pressure only measures the pressure above atmospheric pressure.

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