TP: Using "Steam" Tables (and other tabulated data)

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:

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.