Problem reading thermodynamic tables

In summary, at a given temperature, if the pressure is less than the equilibrium vapor pressure, there will be overheated vapor present. If the pressure is greater than the equilibrium vapor pressure, there will be compressed liquid present. This is because at equilibrium, both pure vapor and pure liquid can exist together, but attempting to change the pressure will result in the vapor or liquid transitioning to the other phase until only one phase remains.
  • #1
Sly37
6
0
Hi!
I have trouble understanding this:
Given Temperature:
If pressure < saturation pressure => Overheated Vapor
If pressure > saturation pressure =>Compressed Liquid


Why does this happen??

Thanks in advance!
 
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  • #2
At a given temperature, you can have both pure vapor and pure liquid present together in equilibrium if the pressure is equal to the equilibrium vapor pressure at that temperature. If you try to increase the pressure by reducing the volume of a fixed amount of liquid and vapor, you won't be able to do it. You will just cause some of the vapor to condense and form more liquid. However, eventually, you will cause all the vapor to condense. After that you will be able to increase the pressure, since only liquid will be remaining.

If you try to decrease the pressure by increasing the volume of a fixed amount of liquid and vapor, you won't be able to do ti. You will just cause some of the liquid to evaporate and form more vapor. However, eventually, youwill cause all the liquid to evaporate. After that, you will be able to reduce the pressure, since only vapor will be remaining. This will be referred to as superheated vapor.
 

1. What are thermodynamic tables used for?

Thermodynamic tables are used to display the properties of substances, such as temperature, pressure, and enthalpy, at different states or conditions. They are commonly used in thermodynamics and engineering to analyze and solve problems related to heat transfer and energy conversion.

2. How do I read a thermodynamic table?

To read a thermodynamic table, first determine the substance or element you are interested in, then locate the desired property (such as temperature or pressure) on the table's axes. Follow the intersecting lines to find the corresponding value for the property at a specific state or condition.

3. What are the units used in thermodynamic tables?

The units used in thermodynamic tables vary depending on the specific table and application. Some common units include Kelvin (K) for temperature, kilopascal (kPa) for pressure, and kilojoule per mole (kJ/mol) for enthalpy. It is important to check the table's units and convert if necessary for accurate calculations.

4. Can I use thermodynamic tables for any substance?

Thermodynamic tables are typically created for specific substances or elements, such as water or air. While some tables may include multiple substances, it is important to ensure that the table is applicable to the substance you are working with before using it for calculations.

5. How accurate are thermodynamic tables?

The accuracy of thermodynamic tables depends on the source and the data used to create them. Tables based on experimental data tend to be more accurate than those based on theoretical calculations. It is important to use reliable and up-to-date tables for accurate results.

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