Determining # of phases given two variables

[mandangalo]

I cannot determine how to figure out how many phases of H20 are present using steam tables given two variables. I have five tables from my old thermodynamics class that are for the following:

Saturated Water: Temperature table
Saturated Water: Pressure table
Saturated Water: Solid-vapor
Superheated Water Vapor
Subcooled Liquid Water

How would I be able to determine how many phases are present give, say, a specific volume of 3 (m^3/kg) at 70 deg celsius? The book doesn't have any examples of how to do so...

 

[Valerie Park]

To find the number of phases of H2O present at a specific volume and temperature, you will need to compare the values in the tables. First, look up the values for the specific volume of 3 (m^3/kg) in the saturated water temperature table and saturated water pressure table. This will give you the corresponding pressure and temperature values. Next, use these pressure and temperature values in the saturated water solid-vapor table to find the specific volume of the vapor phase. Then, compare this specific volume with the initial value of 3 (m^3/kg). If the two values are equal, then there is only one phase of H2O present. If the two values are different, then there are two phases of H2O present. To determine the proportions of each phase, refer to the superheated water vapor table and subcooled liquid water table.