Thermodynamic Properties of Pure Water with an Approach of Multi Input Variable Sets

Abstract

Most of the scientific and engineering problems may be solved by considering temperature and pressure as independent variables, but in some cases we need to consider other variables as independent parameters like the pressure-enthalpy chart, which is of extreme importance for electricity production engineers. Using the IAPWS-95 formulation, an ActiveX component SteamTablesIIE in Visual Basic 6.0 is developed to calculate thermodynamic properties of pure water as a function of two independent intensive variables: (1) temperature (T) or pressure (P) and (2) T, P, volume (V), internal energy (U), enthalpy (H), entropy (S) or Gibbs free energy (G). The second variable cannot be same as variable 1. The following 27 properties are calculated: temperature (T), pressure (P), fraction, state, volume (V), density, compressibility factor (Z0), internal energy (U), enthalpy (H), Gibbs free energy (G), Helmholtz free energy (A), entropy (S), heat capacity at constant pressure (Cp), heat capacity at constant volume (Cv), coefficient of thermal expansion (CTE), isothermal compressibility (Ziso), speed of sound (VelS), partial derivative of P with T at constant V (dPdT), partial derivative of T with V at constant P (dTdV), partial derivative of V with P at constant T (dVdP), Joule-Thomson coefficient (JTC), isothermal throttling coefficient (IJTC), viscosity (Vis), thermal conductivity (Thrm- Cond), surface tension (SurfTen), Prandtl number (PrdNum) and dielectric constant (DielCons). The use of SteamTbalesIIE requires certain precautions because there may be multiple values. Another ActiveX component, SteamTablesGrid is written to store the matrix of V, U, H, S and, G of water for a specified range of temperature and pressure. This is very helpful to speed up and make more efficient the numerical simulation of water and steam flow in a pipeline network.