### Using "Steam" Tables (and other tabulated data)

Recall that the state postulate tells us that knowing two
intensive variables of a pure species fixes all others (i.e., the
state).

##### DEFINITION

A **"steam" tables** typically organize u, s, h, v,
and sometimes g state functions according to (typically) T and
P.

In our book, the steam tables (See Appendix B) include:

- 2 tables for vapor-liquid
- 1 for vapor-solid
- 1 for superheated vapor
- 1 for subcooled liquid.

##### Outcome:

Read desired thermodynamic properties from steam tables

##### NOTE

Often the quantity of interest does not fall at exactly the
tabulated properties.

##### DEFINITION:

**Interpolation** is the calculation procedure that
assumes a straight line between neighboring "points" in a table or
figure in order to estimate an intermediate value.

$\frac{y-y_{1}}{y_{2}-y_{1}} =
\frac{x-x_{1}}{x_{2}-x_{1}}$

$y = y_{1} +(y_{2}-y_{1})*\left( \frac{x-x_{1}}{x_{2}-x_{1}}
\right)$

##### Note:

If both known properties are intermediate to the tabulated data,
**double** interpolation is necessary.

##### Outcome:

Using linear, sometimes double, interpolation to calculate
property values from sparse tabular data

##### Test Yourself:

Calculate the specific volume of superheated water vapor (see
Appendix B.4) at 230 kPa and 460 ${}^\circ$ C.