Use Table C.1b to find the values of p sat, v f, v g, u f, u g, h f, and h g for saturated water at 100.☌. The same notation is used with the intensive properties u and h. This is a convenient way of recording the pair of independent intensive properties used to determine the value of v. psia) means the value of the specific volume at 100.☏ and 50. In Example 3.9, we introduce notation of the form v( X☏, Y psia), which represents the value of the specific volume evaluated at X☏ and Y psia.
It is therefore essential to understand how to determine which table to use in the solution of a thermodynamics problem. It is important to remember that thermodynamic states are unique and a given pair of independent properties fix the state at only one point in the tables. While it is true that any pair of independent properties fix the state of a simple substance subjected to only one work mode, you must be able to deduce the system's thermodynamic state (compressed liquid, saturated liquid or vapor, liquid-vapor mixture, or superheated vapor) from the data given in a problem statement to know in which table to find the other properties required in the analysis. Since your value of p given = 1.0 MPa < p sat = 1.554 MPa, you again conclude that the water must be in a superheated vapor state. From Table C.1 at T given = 200.☌, you find that p sat = 1.554 MPa.
Similarly, if you choose T given = 200.☌ instead of p given, then you would look up p sat at that value of T given. Since your value of T given = 200.☌ > T sat = 179.9☌, the water must be in a superheated vapor state. From Table C.1 at p given = 1.0 MPa, you find that T sat = 179.9☌. Properties Given in the Problem Statementįor example, if you are given water at a pressure of 1.0 MPa and a temperature of 200.☌, then you could choose p given = 1.0 MPa and look up T sat at that value of p given.