水和水蒸气热力性质

代码说明：

 IAPWS_IF97(FUN,IN1,IN2) is 104 functions of water properties and derivatives, based on the International Association on Properties of Water and Steam (http://www.iapws.org). Thermodynamic, hydrodynamic and non-linear modeling often requires thermodynamic derivatives, therefore IAPWS_IF97 can calculate most property derivates as functions of pressure and enthalpy, e.g.: dT/dp_ph, cp_ph, dv/dp_ph and dv/dh_ph. Since modeling often involves multiple dimensions that are discretized or meshed to form a set of either finite-difference or finite-element equations, IAPWS_IF97 is vectorized even across regions (subcooled/compressed-liquid, saturated, superheated and supercritical)