Yr ni nh r 05Ji

a _,r

1 dYr"

Ynn =

d 2y r

r

I dYr"

r

d 2y r

=

d 2y r

Yr =

dn

T

dn2 J

T

Yr =

dr J

jt

Yrr =

3 dr2 6

Equation (18) is valid in the metastable-vapor region from the saturated vapor line to the 5 % equilibrium moisture line (determined from the equilibrium ti and h" values) at pressures from the triple-point pressure, see Eq. (9), up to 10 MPa.

Consistency with the basic equation

The consistency of Eq. (18) with the basic equation, Eq. (15), along the saturated vapor line is characterized by the following maximum inconsistencies regarding the properties v, h, cp , s, g, and w:

|A V | max = 0.014 % |A s | max = 0.082 J kg"1 K"1

|Ah | max = 0.043 kJ kg-1 |Ag | max = 0.023 kJ kg"1 |ACp | max = 0.78 % |A w | max = 0.051 % .

These maximum inconsistencies are clearly smaller than the consistency requirements on region boundaries corresponding to the so-called Prague values [13], which are given in Section 10.

Along the 10 MPa isobar in the metastable-vapor region, the transition between Eq. (18) and Eq. (15) is not smooth, which is however, not of importance for practical calculations.

Computer-program verification

To assist the user in computer-program verification of Eq. (18), Table 18 contains test values of the most relevant properties.

Table 18. Thermodynamic property values calculated from Eq. (18) for selected values of Tand pa

T = 450 K,

T = 440 K,

T = 450 K,

p = 1 MPa

p = 1 MPa

p = 1.5 MPa

v/ (m3 kg 1)

0.192 516 540

0.186 212 297

0.121 685 206

h/ (kJ kg-1)

0.276 881 115 x 104

0.274 015 123 x 104

0.272 134 539 x 104

u/ (kJ kg-1)

0.257 629 461 x 104

0.255 393 894 x 104

0.253 881 758 x 104

s/(kJ kg-1 K-1)

0.656 660 377 x 101

0.650 218 759 x 101

0.629 170 440 x 101

Cp/(kJ kg-1 K-1)

0.276 349 265 x 101

0.298 166 443 x 101

0.362 795 578 x 101

w/ (m s-1)

0.498 408 101 x 103

0.489 363 295 x 103

0.481 941 819 x 103

a It is recommended to verify programmed functions using 8 byte real values for all three combinations of T and p given in this table.

a It is recommended to verify programmed functions using 8 byte real values for all three combinations of T and p given in this table.

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