1. THERMODYNAMICS LAB Properties of Pure Substances
ENTC - 370
ENTC 370
PROF. ALVARADO

2. Substances with fixed chemical composition
Pure Substances
Substances with fixed chemical composition
Examples: Water, Hydrogen, Nitrogen
Homogenous mixture of various components
Examples: Air (combination of oxygen, nitrogen etc.)

3. Pure Substances
It can exist in three different phases- solid, liquid, gas
Under certain conditions, two phases can co-exist
Ex: liquid and gas co-existing in the evaporator and condenser of a refrigerator

4. Property of a substance is independent of the path travelled
Properties of Pure substances
Intensive: Independent of the mass of the substance
Ex: Pressure, Temperature
Extensive: Dependent on the mass of the substance
Ex: Volume, Total Energy, Quality
An Extensive property can be converted to an Intensive property by specifying the property per unit mass, such as specific properties.

5. Pure Substances
A state of a substances can be specified by two independent properties
In single phase, pressure and temperature are the two common independent properties
In two phase, pressure and temperature are no longer independent. In this case we have to use another independent property (mostly “quality”) along with pressure or temperature to determine the state of the substance.

6. Quality The quality of a fluid is the percentage of mass that is vapor
Saturated vapor has a "quality" of 100%
Saturated liquid has a "quality" of 0%
X = 1, Saturated Vapor
X = 0, Saturated Liquid
0 < X < 1, Mixture

7. Example
Suppose that we want to complete the following table of properties for R-134a (‘Refrigerant found in air conditioning systems’):
T [°C]
P [kPa]
V [m3/kg]
Phase Description -8
320
180
Saturated vapor (x = 1.0)
Note: Remember that in order to specify a thermodynamic state, you just need two independent properties.
ENTC 370
PROF. ALVARADO

8. Thermodynamics Properties in EES
EES provides thermophysical property data on a wide variety of fluids that are found in engineering applications
To access this option, in the menu Options, select Function info and The following window will appear
Select the fluid and the property of interest, and paste it to the equations window
ENTC 370
PROF. ALVARADO

9. Properties
Remember EES uses the following representations for the most common properties:
T= temperature
P= Pressure
x= Quality
u= Internal Energy
h= Enthalpy
v= Specific Volume
s= Entropy
Use EES Property Calculator instead of the EES function to fill out the previous table
ENTC 370
PROF. ALVARADO

10. Example
In order to find the missing properties of the first row, we just input the equations, press F2 and get the solutions
ENTC 370
PROF. ALVARADO

11. Example
The second line of the table gives us the pressure and tell us that the refrigerant is in the form of saturated vapor (quality=1).
If we paste the temperature function in the equations window; we will see that the default properties used to calculate the temperature are Pressure and enthalpy
TEMPERATURE(R134a,h=h1,P=P1)
It is possible to change the enthalpy for quality and obtain the temperature
ENTC 370
PROF. ALVARADO

12. Example T [°C] P [kPa] V [m3/kg] The completed table looks like this:
Phase Description -8
320
7.569 * 10-4
Compressed Liquid
-12.73
180
0.1104
Saturated vapor
ENTC 370
PROF. ALVARADO

13. H2O
P=600kPa
Problem 1
A piston-cylinder device contains 0.3 m3 of liquid water and 0.7 m3 of water vapor in equilibrium at 600 kPa. Heat is transferred at constant pressure until the temperature reaches 400 °C.
What is the initial temperature of the water?
Determine the total mass of the water.
Calculate the final volume
Let the final temperature vary from 180 to 1080 °C. Determine the impact on final volume in the tank. Plot the final volume vs. final temperature. Discuss results.
Let the pressure vary from 150 to 1050 kPa. Determine the impact on the final volume of water. Plot the total volume of water vs. Pressure. Discuss results.
ENTC 370
PROF. ALVARADO

14. Lab Report – Problem 1 only
Discussion: State the problem with your own words
Equation: Summary of the equations used in the experiment with explanation.
Findings: Summary of the experimental data, you could use tables, figures, graphs.
Conclusions: Interpretation of the findings.
ENTC 370
PROF. ALVARADO