Only differences in enthalpy are of practical engineering interest .
在实际工程上有意义的只是热含量之差。
A change in enthalpy also takes place when a change of phase occurs .
相发生变化时，焓也发生变化。
The article analyses and sumanzes auto control of humidity , enthalpy and yegulate air volume system by example of clean air codifioning auto cotroling engineering for scientific and research institute .
