水蒸气蒸发过程UDF程序段，fluent关于流体相变的UDF-UDF steam evaporation process block, fluent UDF on fluid phase transition

用快速算法，近似计算调节剂的特性曲线，水蒸气热力性质采用经验公式-With fast algorithms, approximation modifier curve, thermodynamic properties of steam empirical formula