Properties of metastable supercooled steam

For calculation of some thermal processes, first of all of processes of steam expansion in turbines, is important to know properties of a metastable supercooled steam in area adjoining to area 2 formulation on the part of dextral boundary curves. In view of full absence of experimental data about thermodynamic properties of an overcooled water vapor, the calculation them can be conducted only at an extrapolation any of the equation of state which has been compounded(drawn up) for a stable superheated steam, in this area. The outcomes of the analysis of behavior of a series of equations, have shown such as the main equation for area 2 formulation, equation for a superheated steam from formulation IFC-67 and International equation of state for general and scientific application IAPWS-95, that all of them at an extrapolation give the considerably distinguishing data. Such situation is representative of composite multiconstant equations. Therefore as initial for an equation of state of a metastable supercooled steam the data obtained on more simple equation are adopted compounded as auxiliary at mining an International equation of state IAPWS-95 [1].

For calculation of metastable area of a supercooled steam the equation, given in [3] will be used. List of functions for calculating properties of supercooled metastable steam given here.

The equation is applicable for area a metastable steam from the upper boundary curve up to a line 5% of steam humidity in equilibrium h, s - chart at pressure up to 10 MPa. The coordination of values, calculated on it on a line of a saturation with the main equation for area 2 is characterized by the following data:

v|max = 0.014 % s|max = 0.082 J/(kg·K)
h|max = 0.043 kJ/kg g|max = 0.023 kJ/kg
cp|max = 0.78 % w|max = 0.05 %

Along an isobar 10 MPa in the field of a metastable steam transition from an equation for area the metastable steam to an equation for area 2 descends spasmodically, but it has no essential practical value.

The monitoring values of thermodynamic properties of a metastable supercooled steam are adduced in tab. 1.

The table 1. Thermodynamic properties of a metastable supercooled steam
Property t = 450 K, P = 1 MPa t = 440 K, P = 1 MPa t = 450 K, P = 1.5 MPa
v, m3/kg 0.192516540 0.186212297 0.121685206
h, kJ/kg 0.276881115·104 0.274015123·104 0.272134539·104
u, kJ/kg 0.257629461·104 0.255393894·104 0.253881785·104
s, kJ/(kg·K) 0.656660377·101 0.650218759·101 0.629170440·101
cp, kJ/(kg·K) 0.276349265·101 0.298166443·101 0.362795578·101
w, m/sec 0.498408101·103 0.489363295·103 0.481941819·103