| Abstract |
H2O is one of the fluids that has been more and better theoretically and experimentally investigated worldwide. The thermodynamic behavior of water has a crucial importance in a multitude of scientific and industrial applications of geothermal energy. The International Association for the Properties of Water and Steam (IAPWS) is an organization responsible for the international standardization of the thermophysical water properties. This includes an equation of state of ordinary H2O for general and scientific use. The IAPWS-95 formulation is based on the Helmholtz's free energy as the fundamental potential that is a function of both, the density and the temperature of water. All other thermodynamic properties can be obtained by partial differentiation and algebraic manipulation of the corresponding Helmholtz surface f(rho,T). We constructed a useful computer code of this formulation for water properties within an interactive graphical interface using the programming language of the software Mathematica, version 9. The properties shown in this paper are the most useful in geothermal engineering practice: pressure, specific volume, entropy, enthalpy, internal energy, dynamic and kinematic viscosity, isothermal compressibility, specific heat and thermal conductivity. These properties are computed separately for each phase, liquid and vapor, in a wide thermodynamical range. The program calculates also the saturation pressure and temperature in the K-line for two-phase water. All the properties are computed with high numerical precision covering all experimentally measured ranges and reported in the IAPWS-95 formulation. The powerful graphical interface of the code allows displaying immediately any of the H2O properties in 2D and 3D graphics simultaneously. The covered range of temperatures goes from 0°C to 4730°C and for pressures it goes from 0.1 MPa (1 bar) to 100 GPa (106 bar). We used highly efficient algorithms based on the IAPWS-95 formulation. The computer program is original, freely available and can be used in all type of geothermal systems of low, medium, high and supercritical enthalpy. Examples are presented to illustrate the code for critical and supercritical conditions. The code is useful in practical and theoretical geothermal research and is a valuable didactic tool for any person interested in geothermal water properties. |