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3.4.2 Vapour pressure of water at temperatures between 0 and 360°C

The table has been calculated from the equation given by Wagner and Pruss (1993)

ln(p/pc) = (a1τ + a2τ1.5 + a3τ3 + a4τ3.5 + a5τ4 + a6τ7.5)Tc/T,

where p is the pressure, T = T90, and subscript c indicates the values at the critical point; τ = 1 − T/Tc. The values for substitution in the equation are:

Tc = 647.096K     pc = 220 64 kPa     a1 = −7.859 51783     a2 = 1.844 082 59

a3 = −11.786 6497     a4 = 22.680 7411     a5 = −15.961 8719      a6 = 1.801 225 02

Pressures are tabulated in kPa for Celsius temperatures t90. For example, at 34 °C the pressure is 5.3240 kPa and at 102°C is 108.87 kPa.

t/°C

0

2

4

6

8

10

12

14

16

18

                     

0

    0.6112

    0.7060

      0.8135

    0.9353

       1.0729

    1.2281

   1.4027

    1.5989

   1.8187

     2.0646

20  

    2.3392

    2.6452

      2.9857

    3.3638

       3.7809

    4.2452

   4.7582

    5.3240

    5.9472

     6.6324

40  

    7.3848

    8.2096

      9.1126

10.100

   11.117

12.352

13.632

15.023

16.534

18.173

60  

19.948

 21.869

  23.946

26.188

   28.605

 31.210 

34.013

37.010

40.240

43.704

80  

47.416

 51.388

  55.636

60.174

   65.018

70.183

75.685

81.542

87.771

94.390

100    

101.42    

108.87   

116.78  

125.15    

134.01  

143.38    

153.28    

163.74   

174.77    

186.41    

120    

198.67    

211.59   

225.18  

239.47   

254.49  

270.28    

286.84   

304.22   

322.44   

341.54    

140    

361.53    

382.46   

404.36  

427.25   

451.17  

476.16    

502.24   

529.45   

557.83   

587.41    

160    

618.23    

650.32   

683.73  

718.48   

754.62  

792.18    

831.22   

871.75   

913.84   

957.51    

180    

1002.8       

1049.8      

1098.5     

1148.9       

1201.2      

1255.2       

1311.2      

1369.1       

1429.0        

1490.9        

200    

1554.9       

1621.0      

1689.3     

1759.8       

1832.6      

1907.7       

1985.1      

 2065.0         

2147.3        

2232.2       

 

 

 

 

 

 

 

 

 

 

 


t/°C

 

 

220

240

260

280

300

  320

    340

   360

p/kPa

2319.6

3347.0

4692.3

6416.6

8587.9

11 284

14 601

18 666


The pressure at the triple point, 273.16 K, is 0.611 657 kPa and the temperature at which the pressure is one standard atmosphere, 101.325 kPa, is 372.124 K (99.974 °C). Change in the temperature T with change in pressure p in the region of atmospheric pressure may be calculated from the following equation applicable in the range 95 °C to 105 °C (85 kPa to 120 kPa):

   ln(p/kPa) = 16.166 29 − 3736.276/((T/K) − 49.577)




Reference

W. Wagner and A. Pruss (1993) J. Phys. Chem. Reference Data, 22, 783–787.




D.Ambrose

 

 

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