Page 185 - Advanced Thermodynamics for Engineers, Second Edition

172 CHAPTER 8 EQUATIONS OF STATE

250

7
200

Pressure, p / (bar) 150 6 4 I 3 2

100 II 1

5
50
0 0.005 0.010 0.015 0.020 0.025 0.030
3
Specific volume, v /(m /kg)
FIGURE 8.4

Variation of pressure and specific volume for water along the 300 C isotherm.
This variation has been calculated for the region between points 1 and 7 in Fig. 8.4, and is shown
in Fig. 8.5.
It can be seen from Fig. 8.5 that the Gibbs energy increases along the isotherm from point 1 to
point 3. Between point 3 and point 5 the Gibbs energy decreases, but then begins to increase again

200

175

7 3
150
Pressure, p / (bar) 125 1
2,4,6

100

75
5
50
Variation of Gibbs energy along an isotherm
FIGURE 8.5
Variation of Gibbs energy for water along the 300 C isotherm.