The Steam Tables
The graphical representations of Figures 2.8 and 2.9 are valuable for understanding the general features of the pvT properties of water but are of little use for quantitative analysis. For this purpose, extensive tables of the thermodynamic properties of water have been compiled. Such tabular information is available for many condensable substances in addition to water. For the latter, the property listings are called the steam tables, although they contain data for liquid water and ice as well as for the vapor phase. The steam considered in the tables is pure, undiluted by other gases such as air. Mixtures of water vapor and noncondensible gases are considered in Chapter 5.
In addition to listing the numerical values of the pvT properties illustrated in Figures 2.8 and 2.9, the steam tables present a complete listing of the thermal properties h and s. Tables 2.22.5 are condensed versions of these tabulations. Complete tables can be found in the appendices of References 4 and 5.
2.7.1 TwoPhase Saturated LiquidSaturated Vapor
Table 2.2 contains properties of saturated water, both gaseous (denoted by subscript^) and liquid (subscript f). These are the numerical values along the heavyline, twophase envelope in the Tv projection of Figure 2.9. The first two columns of Table 2.2 gives the coordinates of the L/V line in the pT projection of Figure 2.9. That is, these data represent the vapor pressure of liquid water. Like the line in righthand graph of Figure 2.9, the pT properties in the saturatedwater table start at the triple point and end at the critical point.
The intervals of temperature,and jpressure in Table 2.2 are designed so that intermediate values can be obtained with reasonable accuracy by linear interpolation. Using Table 2.2, for example, the vapor pressure at 73°C is determined by solving the following equation for p^ (73°C):
Psai(73°C)psg,(70°C) _ jPjb>(73°C)312 ^ 7370 Psa (75°C)  pM (70°C) 386312 7570
The variable absent from Table 2.2 is the volume v. The reason is that in a twophase region, Equation (2.20) shows that the system volume depends on the quality (steam mass fraction) in addition to the specific volumes vf and vg of the saturated liquid and vapor phases. The latter are listed in the third and fourth columns of the table. The quality x is not a thermodynamic property; it can vary between 0 and 1. Internal energy (u), enthalpy (h) and entropy (s) are handled in the same manner as described above for the specific volume (v).
Getting Started With Solar
Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.
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