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How to Obtain Data From Tables

In the previous lesson, we discussed the relationships between pressure, temperature and volume. We focused on understanding the nature of phases and phase changes by studying phase diagrams. Now, we will turn our attention to determining pressure, volume, temperature and other properties from tables of thermodynamic data.

In this lesson, we will study all three parts of a typical set of thermodynamic tables.

Saturation Temperature Tables

Saturation Pressure Tables

Subcooled Liquid Tables

Superheated Vapor Tables

We will only consider water in this lesson, but thermodynamic tables for ammonia and the refrigerant R-134a are also provided in the Ch 2 First Aid Kit.

Lesson 2C: page 1 of 24

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Ch2, Lesson C, Page 1 - How to Obtain Data From Tables

In the previous lesson, we introduced the concept of phase diagrams.
Phase diagrams are graphical representations of the relationships between pressure, volume and temperature.
As wonderful as phase diagrams are for helping to understand and visualize phases and phase changes, it is not very easy to accurately obtain numerical values from them.
Consequently, vast amounts of thermodynamic data have been compiled in tabular form.
As you might imagine, these tables are very large and take up many pages each.
The goal of this lesson is to learn how to quickly and accurately obtain the values you need from thermodynamic tables.
Now, the catch is that a set of thermodynamic tables for a given substance comes in 4 parts.
The 1st two parts provide the properties of sat’d liquids and sat’d vapors.
So, why are there 2 parts that provide the same information ?
Well, one part contains rows of data evaluated at nice even values of temperature.
The other part has rows of data evaluated at nice even values of pressure.
That’s why the two parts are called the saturation temperature tables and the saturation pressure tables.
The properties of superheated vapors occupy a separate section of their own.
The properties of subcooled liquids also have their own section in a complete set of thermodynamic tables.
That may sound a bit scary, but we’ll work it all out in great detail so that you feel confident about using thermodynamic tables.
In this lesson, we’ll only use the thermodynamic tables for water, ammonia and a refrigerant called R-134a.
The thermodynamic tables for steam are always called the steam tables even though they include the properties of liquid water as well.
You will find the steam tables as well as the thermodynamic tables for two common refrigerants, ammonia and R-134a, in the Ch2 1st Aid Kit.
These 2 refrigerants are popular because they are environmentally friendly and you will lean more about these and other refrigerants in Chapter 9.
But right now, let’s learn about thermodynamic tables.

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